NAT L INST OF STAND & TECH R.j^C. NIST X3/TR-1—77 PUBLICATIONS -SniDB 517103 1977 SEPTEMBER

X3 TECHNICAL REPORT

Adopted tor Use by the Federal Government

AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

FIPS 11-1

See Notice on Inside Front Cover

M AMERICAN NATIONAL STANDARDS COMMITTEE X3 — COMPUTERS & INFORMATION PROCESSING JKm - ■ PRsA2> tlD II- I iq-n ab( TTTli This DICTIONARY has been adopted for Federal Government use as a basic reference document to promote a common understanding of information processing terminology. Details concerning the specific use of this DICTIONARY are contained in Federal Information Processing Standards Publication 11-1, DICTIONARY FOR INFORMATION PROCESSING For a complete list of publications avail¬ able in the FIPS Series, write to the Office of ADP Standards Management, Institute for Computer Sciences and Technology, National Bureau of Stan¬ dards, Washington, D C 20234 f-^oftH QvlasviStzaiiTft DEC 71378 not (\Cc-;<£ Secretariat: ComputerandBusinessEquipment ManufacturersAssociation

SKI X3 —ComputersandInformationProcessing American NationalDictionary American NationalStandardsCommittee Information Processing for X3/TR-1-77 1977 September Published by

Computer and Business Equipment Manufacturers Association 1828 L Street NW, Washington DC 20036 202/466-2299

Copyright © 1977 by Computer and Business Equipment Manufacturers Association All rights reserved.

Permission is herby granted for quotation, with accreditation to "American National Dictionary for Information Processing, X3/TR-1-77". of up to fifty terms and their definitions. Other than such quotation, no part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.

Printed in the United States of America. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 1

Foreword The communication of facts and ideas de¬ The members of Technical Committee pends upon a mutual understanding of who participated in the development of terminology. This is particularly true in this Dictionary were: the rapidly growing field of information processing, in which there is a continuing M. H. Weik, Jr., Chairman need for a comprehensive source of tech¬ J. R. Wood, Vice-Chairman nical terms and definitions. J. L. Walkowicz, Secretary E. A. Anderson By direction of the American National L. A. Difford Standards Committee on Computers and P. M. Gaynor Information Processing (X3) the Technical C. R. Gethmann Committee on Vocabulary (X3K5) pre¬ Dr. S. Gorn pared this American National Dictionary F. T. Grampp for Information Processing (ANDIP). The R. R. Hegland Dictionary is based on the American Na¬ T. D. C. Kuch tional Standard Vocabulary for Informa¬ T. Leach tion Processing, X3.12-1970, published by R. P. Mullinax the American National Standards Institute. A. J. Neumann The Dictionary was developed not only Dr. G. Patterson (Deceased) by combining existing lexicons, but also R. D. Pngge by studying the use of terms throughout H. E. Thiess the field of computers and information C. K. Vanderhoof processing. Technical Committee X3K5, in consultation with other X3 technical Sequence of Entries committees, used proposed and approved The sequence of entries in this Dictionary American national standards and vocabu¬ is determined on a letter-by-letter basis, in laries submitted by other bodies as the other words, only the letters of the alpha¬ sources of terms and definitions. The bet are used to determine the sequence of Dictionary influenced the development of entries. sections of the International Organization for Standardization Vocabulary of Data Processing, prepared by ISO Technical Organization of an Entry Committee 97, Subcommittee 1 (ISO/TC An entry consists of a term or the ab¬ breviation or acronym for a term followed 97/SC 1), and includes terms and defini¬ by a commentary. When a commentary tions from that vocabulary. includes several different definitions for that term, each definition is a separate Advances in the field of information proc¬ item. When an item is used to refer to essing cause changes in terminology. all the terms having the same last word, Suggestions for changes or additions to it lists all of these terms in natural order this document should be addressed to the and precedes this list with the word Computer and Business Equipment “See”. Manufacturers association, 1828 L Street NW, Washington, DC 20036. 2 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

Selection of Terms disciplines) A term is a word or group of words to (16) International Definitions be defined. In this Dictionary, the singu¬ (17) USA Definition lar form of the noun and the infinitive (18) References form of the verb are the terms most often

selected to be defined. If the term can Each item may include an item number, a be abbreviated, the abbreviation is given source label, a usage label, a descriptive in parentheses immediately following the phrase, an annotation, and a reference to term. other terms, in that order.

Organization of a Commentary Item Number A commentary consists of one or more Each item in a commentary is numbered items (definitions or references) arranged consecutively starting with item (1). If in the following order: the commentary consists of only one item, the item number is omitted. Noun Form General Definitions Source Label (1) International Definition This label precedes the definition and (2) USA Definition identifies the source of the definition. (3) References Definitions bearing the source label (ISO) are based on material developed by the Specific Definitions (for special International Organization for Standardiza¬ disciplines) tion. All other definitions are based on (4) International Definition sundry authoritative sources. (5) USA Definition (6) References

Usage Label Verb Form (if applicable) This label is a word or phrase that indi¬ General Definitions cates the area or manner of usage of the (7) International Definition (8) USA Definition item. For example, the label “In (9) References programming” indicates an area of usage, and the label “Loosely,” indicates a man¬

Specific Definitions (for special ner of usage. The usage label is followed disciplines) by a comma. (10) International Definition (11) USA Definition Descriptive Phrase (12) References This states, or provides an initial state¬ ment of, the definition of the term and Adjective Form (if applicable) may be assumed to be preceded by the General Definitions phrase, “(the term) is defined as.” The (13) International Definition descriptive phrase completes the initial ( 14) USA Definition sentence. The part of speech of the term (15) References being defined is indicated by the introduc¬ tory words in the descriptive phrase, Specific Definitions (for special where the word “to” indicates a verb. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 3

“pertaining to” indicates a modifier, and as described below. The reference sym¬ other words indicate a noun. bols are described in the order in which they would occur within an entry: Annotation

This part of the definition consists of any Deprecated term for. Indicates that the number of complete sentences. These term should not be used (because it is sentences follow the descriptive phrase obsolete, misleading, ambiguous, or and provide additional descriptive or ex¬ jargon) and refers to the preferred term. planatory information.

Synonymous with. Identifies terms that References have the same meaning as the defined A reference consists of a symbol or term, and which refer to the defined term phrase to direct the user to another item with a “Synonym for” reference symbol. in the same commentary or to another en¬ try or item in the Dictionary. If the term Synonym for. Refers to a defined term being defined is an acronym or abbrevia¬ that has the same meaning. tion, the complete unabbreviated term is given and the term is defined in a sepa¬ Contrast with. Refers to a term that rate entry (except where the abbreviation has an opposite or substantively different or acronym is predominantly used; e.g., FORTRAN.) An italicized term occurring meaning. in a commentary indicates that the term, or a grammatically different form of it, See. Refers to multiple-word terms that has been defined elsewhere in the Dic¬ have the same last word or words. tionary. Also, the reference symbols (De¬ precated term for. Synonymous with. See also. Refers to related terms that Synonym for. Contrast with. See, and See have a similar, but not synonymous, also) explain the nature of the reference meaning. 4 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

A abstract symbol (1) (ISO) A symbol whose meaning and use have not been determined by a general agreement but have to be de¬ fined for each application of the sym¬ absolute address bol. (1) (ISO) An address in a computer lan¬ (2) In optical character recognition, a guage that identifies a storage location symbol whose form does not suggest or a device without the use of any in¬ its meaning and use; these should be termediate reference. defined for each specific set of ap¬ (2) An address that is permanently as¬ plications. signed by the machine designer to a

storage location. access (3) Synonymous with explicit address, ma¬ See direct access, direct access storage, im¬ chine address, specific address. mediate access storage, random access, remote access, serial access. absolute addressing

(ISO) A method of addressing in which access arm the address part of an instruction contains A part of a disk storage unit that is used an absolute address. to hold one or more reading and writing heads. absolute coding

Coding that uses computer instructions access mode with absolute addresses. Synonymous A technique that is used to obtain a with specific coding. specific logical record from, or to place a specific logical record into, a file assigned absolute error to a mass storage device. (1) (ISO) The algebraic result of subtract¬

ing a true, specified, or theoretically access time correct value from the value comput¬ (1) (ISO) The time interval between the ed, observed, measured, or achieved. instant at which an instruction control (2) The amount of error expressed in the unit initiates a call for data and the same units as the quantity containing instant at which delivery of the data the error. is completed. Access time equals la¬ (3) Loosely, the absolute value of the er¬ tency plus transfer time. ror, i.e., the magnitude of the error (2) The time interval between the instant without regard to its algebraic sign. at which data are requested to be stored and the instant at which stor¬ absolute instruction age is started. (ISO) A computer instruction in its final, (3) (ISO) Deprecated term for cycle time. executable form.

accounting machine absolute loader ( 1) A keyboard-actuated machine that A routine that reads a computer program prepares accounting records. into main storage, beginning at the assem¬ (2) A machine that reads data from exter¬ bled origin. nal storage media, such as cards or AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 5

tapes, and automatically produces ac¬ acoustic delay line counting records or tabulations, usually A delay line whose operation is based on on continuous forms. time of propagation of sound waves in a (3) See electrical accounting machines. given medium. Synonymous with sonic delay line.

accumulator (ISO) A register in which the result of an acoustic memory operation is formed. Deprecated term for acoustic storage.

acoustic storage accuracy A storage device consisting of acoustic (1) (ISO) A quality held by that which is delay lines. free of error. (2) (ISO) A qualitative assessment of free¬ actual instruction dom from error, a high assessment (ISO) Deprecated term for effective in¬ corresponding to a small error. struction. (3) (ISO) A quantitative measure of the magnitude of error, preferably ex¬ actual key pressed as a function of the relative In COBOL, a key that directly expresses error, a high value of this measure the physical location of a logical record corresponding to a small error. on a mass storage medium. (4) Contrast with precision.

add accuracy control character See false add. A control character used to indicate whether the data with which it is associat¬ addend ed are in error or are to be disregarded, (ISO) In an addition operation, a number or cannot be represented on a particular or quantity added to the augend. device. Synonymous with error control character. adder (1) (ISO) A device whose output data are ACK a representation of the sum of the The acknowledge character. numbers represented by its input data. (2) A device whose output is a represen¬ acknowledge character (ACK) tation of the sum of the quantities (1) (ISO) A transmission control character represented by its inputs. transmitted by a station as an affirma¬ (3) See full adder, half adder, parallel tive response to the station with which adder, serial adder. the connection has been set up. (2) A transmission control character trans¬ adder subtracter mitted by a receiver as an affirmative (ISO) A device that acts as an adder or response to a sender. An acknowl¬ subtracter depending upon the control sig¬ edge character may also be used as nal received. The adder subtracter may an accuracy control character. be constructed so as to yield the sum and (3) See negative acknowledge character. the difference at the same time. 6 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

addition addressable vertical positions See parallel addition, serial addition. (1) In micrographics, the number of posi¬ tions, within a specified film frame, at

addition without carry which a horizontal line can be placed. (ISO) Deprecated term for non-equiva¬ (2) In computer graphics, the number of lence operation. positions, within a specified raster, at which a full length horizontal line can be placed. address ( 1) (ISO) A character or group of charac¬ address format ters that identifies a register, a par¬ (1) The arrangement of the address parts ticular part of storage, or some other of an instruction. The expression data source or destination. plus-one is frequently used to indicate (2) (ISO) To refer to a device or an item that one of the addresses specifies the of data by its address. location of the next instruction to be (3) See absolute address, base address, di¬ executed, such as one-plus-one, two- rect address, effective address, four address, four-plus-one address, plus-one, three-plus-one, four-plus-one. (2) The arrangement of the parts of a generated address, immediate address, indexed address, indirect address, in¬ single address, such as those required for identifying channel, module, track, struction address, machine address, multiaddress, multilevel address, n- etc. in a magnetic disk system. level address, one-level address, real address, relative address, relocatable addressing address, self-relative address, single- See absolute addressing, deferred address¬ address, specific address, symbolic ad¬ ing, direct addressing, immediate address¬ dress, synthetic address, two-level ad¬ ing, implied addressing, indirect address¬ dress, virtual address, zero-level ad¬ ing, one-ahead addressing, relative ad¬ dress. dressing, repetitive addressing, self-relative addressing, symbolic addressing.

addressability In micrographics, the number of addressa¬ address modification ble positions, within a specified film Any arithmetic, logic or syntactic operation frame, as follows: number of addressable performed on an address. horizontal positions by number of address¬ able vertical positions, e.g., 4000 by 4000. address part (ISO) A part of an instruction that usual¬

addressable horizontal positions ly contains only an address or part of an (1) In micrographics, the number of posi¬ address. tions, within a specified film frame, at which a vertical line can be placed. address register (2) In computer graphics, the number of ( 1) A register in which an address is positions, within a specified raster, at stored. which a full length vertical line can (2) See base address register, instruction be placed. address register. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 7

address track alias (ISO) A track that contains addresses. An alternate label. For example, a label and one or more aliases may be used to

adjacency refer to the same data element or point In character recognition, a condition in in a computer program. which the character spacing reference lines allocation of two consecutively printed characters See dynamic storage allocation, storage al¬ printed on the same line are separated by location. less than a specified distance.

alphabet administrative data processing (1) (ISO) An ordered set of all the letters (ISO) Automatic data processing used in used in a language, including letters accounting or in management. Synony¬ with diacritical signs where appropri¬ mous with business data processing. ate, but not including punctuation marks. ADP (2) An ordered set of symbols used in a Automatic data processing. language, e.g., the Morse code alpha¬ bet, the 128 ASCII characters. algebraic language

An algorithmic language many of whose alphabetic character set statements are structured to resemble the (ISO) A character set that contains letters structure of algebraic expressions, e.g., AL¬ and may contain control characters, spe¬ GOL, FORTRAN. cial characters, and the space character, but not digits.

algebraic manipulation The processing of mathematical expres¬ alphabetic character subset sions without concern for the numeric va¬ (ISO) A character subset that contains let¬ lues of the symbols that represent num¬ ters and may contain control characters, special characters, and the space character, bers. but not digits.

ALGOL(Algorithmic language) alphabetic code A language used to express computer pro¬ (ISO) A code according to which data is grams by algorithms. represented using an alphabetic character set. algorithm (ISO) A finite set of well-defined rules for alphabetic coded character set the solution of a problem in a finite num¬ (ISO) A coded character set whose ber of steps, e.g., a full statement of an character set is an alphabetic character arithmetic procedure for evaluating sin x set. to a stated precision.

alphabetic string algorithmic language (1) (ISO) A string consisting solely of let¬ (ISO) An artificial language established ters from the same alphabet. for expressing algorithms. (2) A character string consisting solely of 8 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

letters and associated special characters analog from the same alphabet. (1) (ISO) Pertaining to representation by means of continuously variable physi¬ alphabetic word cal quantities. (1) (ISO) A word consisting solely of let¬ (2) Contrast with digital, discrete. ters from the same alphabet. (3 ) See network analog. (2) A word consisting of letters and as¬ sociated special characters, but not di¬ analog computer gits. ( 1) (ISO) A computer in which analog re¬ presentation of data is mainly used. alphameric (2) A computer that operates on analog Synonym for alphanumeric. data by performing physical processes on these data. alphanumeric (3) Contrast with digital computer. Pertaining to a character set that contains letters, digits, and usually other characters analog data such as punctuation marks. Synonymous (ISO) Data represented by a physical with alphameric. quantity that is considered to be contin¬ uously variable and whose magnitude is alphanumeric character set made directly proportional to the data or (ISO) A character set that contains both to a suitable function of the data. letters and digits and may contain control characters, special characters, and the analog representation space character. (ISO) A representation of the value of a variable by a physical quantity that is alphanumeric character subset considered to be continuously variable, the (ISO) A character subset that contains magnitude of the physical quantity being both letters and digits and may contain made directly proportional to the variable control characters, special characters, and or to a suitable function of the variable. the space character. analysis alphanumeric code (1) The methodical investigation of a (ISO) A code according to which data is problem, and the separation of the represented using an alphanumeric charac¬ problem into smaller related units for ter set. further detailed study. (2) See flow analysis, numerical analysis. alphanumeric coded character set (ISO) A coded character set whose analyst character set is an alphanumeric character (ISO) A person who defines problems and set. develops algorithms and procedures for their solution. alphanumeric data (ISO) Data represented by letters and di¬ analyzer gits, perhaps with special characters and See differential analyzer, digital differential the space character. analyzer, network analyzer. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 9

AND aperture card (ISO) A logic operator having the proper¬ A processable card of standard dimensions ty that if P is a statement, Q is a state¬ into which microfilm frames can be insert¬ ment, R is a statement. then the AND ed. of P,Q,R... is true if all statements are true, false if any statement is false. P aperture core AND Q is often represented by P*Q, PQ, See multiple aperture core. PAQ. Synonymous with logical multiply. application-oriented language AND element A problem-oriented language whose state¬ (1) (ISO) A logic element that performs ments contain or resemble the terminology the boolean operation of conjunction. of the occupation or profession of the us¬ (2) Synonym for AND gate. er, e.g., a report program generator.

AND gate arbitrary sequence computer (1) A gate that implements the logic (ISO) A computer in which each instruc¬ AND operator. tion explicitly determines the location of (2) Synonym for AND element. the next instruction to be executed.

AND-not operation architecture (ISO) Deprecated term for exclusion. See computer architecture.

AND operation argument (ISO) Synonym for conjunction. (1) (ISO) An independent variable. (2) (ISO) Any value of an independent

annotation variable. An added descriptive comment or ex¬ planatory note. arithmetical instruction (ISO) Synonym for arithmetic instruction. anticipatory buffering A technique by which data are stored in arithmetic and logic unit a buffer before they are needed. (ISO) A part of a computer that performs arithmetic operations, logic operations, and

aperture related operations. (1) (ISO) One or more adjacent charac¬ ters in a mask that cause retention of arithmetic check the corresponding characters. Synonym for mathematical check. (2) An opening in a data medium or de¬ vice such as a card or magnetic core; arithmetic instruction e.g., the aperture in an aperture card (ISO) An instruction in which the opera¬ combining a microfilm with a punched tion part specifies an arithmetic operation. card, or in a multiple aperture core. Synonymous with arithmetical instruction. (3) A part of a mask that permits reten¬ tion of the corresponding portions of arithmetic operation data. (1) (ISO) An operation that follows the (4) See multiple aperture core. rules of arithmetic. 10 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(2) See binary arithmetic operation. arithmetic unit (ISO) A part of a computer that performs arithmetic overflow arithmetic operations, and related opera¬ (1) (ISO) That portion of a numeric word tions. expressing the result of an arithmetic operation by which its word length array exceeds the word length provided for An arrangement of elements in one or the number representation. more dimensions. Synonymous with overflow. (2) (ISO) That portion of a word express¬ array pitch ing the result of an operation by Synonym for row pitch. which its word length exceeds the storage capacity of the intended stor¬ artificial intelligence age device. (1) The capability of a device to perform functions that are normally associated arithmetic register with human intelligence, such as rea¬ (ISO) A register that holds the operands soning, learning, and self-improvement. or the results of operations such as arith¬ (2) See also machine learning. metic operations, logic operations, and shifts. artificial language (1) (ISO) A language whose rules are ex¬ arithmetic shift plicitly established prior to its use. (ISO) A shift, applied to the representa¬ (2) Contrast with natural language. tion of a number in a fixed-radix numera¬ tion system and in a fixed-point represen¬ ASCII (American National Standard Code tation system, in which only the characters for Information Interchange) representing the absolute value of the The standard code, using a coded charac¬ number are moved. An arithmetic shift is ter set consisting of 7-bit coded characters usually equivalent to multiplying the num¬ (8-bits including parity check), used for ber by a positive or a negative integral information interchange among data proc¬ power of the radix except for the effect essing system, data communication sys¬ of any rounding. tems, and associated equipment. The AS¬ CII set consists of control characters and arithmetic underflow graphic characters. (ISO) In an arithmetic operation, a result whose absolute value is too small to be assemble represented within the range of the nu¬ (1) (ISO) To translate a program ex¬ meration system in use. For example, the pressed in an assembly language into condition existing, particularly when a a computer language and perhaps to floating-point representation system is link subroutines. Assembling is usual¬ used, when the result is smaller than the ly accomplished by substituting the non-zero quantity that can be represented; computer language operation code for the result may underflow because of the the assembly language operation code generation of a negative exponent that is and by substituting absolute addresses, outside the permissable range. immediate addresses, relocatable ad- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 11

dresses, or virtual addresses for sym¬ with machine instructions. bolic addresses. Synonymous with computer-dependent (2) To prepare a machine language pro¬ language, computer-oriented language. gram from a symbolic language pro¬ gram by substituting absolute opera¬ assembly phase tion codes for symbolic operation (ISO) Of a run, the logical subdivision codes and absolute or relocatable ad¬ that includes the execution of the assem¬ dresses for symbolic addresses. bler. Synonymous with assembling phase.

assemble-and-go assembly program An operating technique in which there are (ISO) Synonym for assembler. no stops between the assembling, loading, and execution of a computer program. assignment statement (1) An instruction used to express a se¬ assembled origin quence of operations, or used to as¬ The address of the initial storage location sign operands to specified variables, or assigned to a computer program by an as¬ symbols, or both. sembler, a compiler, or a linkage editor. (2) In COBOL, a statement used to as¬ sociate a file with the symbolic name assemble duration of a device. (ISO) Synonym for assembling time.

associative storage assembler (1) (ISO) A storage device whose storage (ISO) A computer program used to as¬ locations are identified by their con¬ semble. Synonymous with assembly pro¬ tents, or by part of their contents, gram. rather than by their names or posi¬ tions. Synonymous with content- assembling phase addressed storage. (ISO) Synonym for assembly phase. (2) Contrast with parallel search storage.

assembling time asynchronous computer (ISO) The elapsed time taken for the exe¬ (1) (ISO) A computer in which each cution of an assembler. Synonymous with event or the performance of each op¬ assemble duration. eration starts as a result of a signal generated by the completion of the assembly language previous event or operation, or on the (1) (ISO) A computer-oriented language availability of the parts of the com¬ whose instructions are usually in one- puter required for the next event or to-one correspondence with computer operation. instructions and that may provide (2) Contrast with synchronous computer. facilities such as the use of macro- instructions. asynchronous operation (2) A computer programming language (1) (ISO) An operation that occurs with¬ whose statements may be instructions out a regular or predictable time rela¬ or declarations. The instructions usu¬ tionship to a specified event, e.g., the ally have a one-to-one correspondence calling of an error diagnostic routine 12 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

that may receive control at any time automatic control engineering during the execution of a computer (ISO) That branch of science and tech¬ program. nology which deals with the design and (2) A sequence of operations in which op¬ use of automatic control devices and sys¬ erations are executed out of time coin¬ tems. cidence with any event. (3) Synonymous with asynchronous work¬ automatic data processing (ADP) ing. (1) (ISO) Data processing largely per¬ formed by automatic means. asynchronous working (2) (ISO) The branch of science and tech¬ (ISO) Synonym for asynchronous opera¬ nology concerned with methods and tion. techniques relating to data processing largely performed by automatic means.

attribute (3) Pertaining to data processing equip¬ See data attribute. ment such as electrical accounting ma¬ chines and electronic data processing

augend equipment. (ISO) In an addition operation, a number or quantity to which numbers or quantities automatic-feed punch are added. A punch that automatically moves punch cards from a card hopper, along a card automated data medium path and to a card stacker. Synonym for machine readable medium.

automatic programming automatic The process of using a computer to per¬ (ISO) Pertaining to a process or device form some stages of the work involved in that, under specified conditions, functions preparing a computer program. without intervention by a human operator. Synonymous with automatic coding.

automatic carriage automatic punch A control mechanism for a typewriter or Synonym for card punch. other listing device that can automatically control the feeding, spacing, skipping, and automation ejecting of paper or preprinted forms. (1) (ISO) The implementation of processes by automatic means. automatic check (2) (ISO) The conversion of a procedure, ( 1) A check performed by equipment a process, or equipment to automatic built-in specifically for checking pur¬ opation. poses. Synonymous with built-in (3) The theory, art, or technique of mak¬ check, hardware check. ing a process more automatic. (2) Contrast with programmed check. (4) The investigation, design, development, and application of methods of render¬ automatic coding ing processes automatic, self-moving, Synonym for automatic programming. or self-controlling. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 13

auxiliary operation The average information rate may be ex¬ An offline operation performed by equip¬ pressed in a unit such as Shannon per se¬ ment not under control of the central cond. processing unit.

auxiliary storage average transinformation content (1) (ISO) A storage device that is not (ISO) Synonym for mean transinformation maw storage. content. (2) Storage that supplements another stor¬ age. (3) Contrast with main storage. average transinformation rate

The mean transinformation content per available time character per time unit; in mathematical (1) (ISO) The time during which a func¬ tional unit can be used. notation this T* equals the mean transin¬ (2) Synonymous with uptime. formation content per character T' divided (3) Contrast with maintenance time. by the mathematical expectation, T of the

duration T- of any one pair of characters average conditional information content x, y from sets x.x and y.y ; i j j i n j i J m (ISO) Synonym for conditional entropy.

average information content (ISO) Synonym for entropy. n m

T* = T where r = ^ rijp(x.,y.) average information rate T i= 1 /= 1 (ISO) In information theory, the mean entropy per character per time unit; in mathematical notation, this H* equals the mean entropy per character H' divided by the mathematical expection T of the dura¬ The average transinformation rate per tion T of any one character xi from the time may be expressed in a unit such as character set x.x : i n Shannon per second.

n

H* - H' where t = Tp(x) t / = 1 14 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

B balanced merge sort (1) A merge sort, which is an external sort, such that the sorted subsets background processing created by the internal sorts are (1) The execution of lower priority com¬ equally distributed among half of the puter programs when higher priority available auxiliary storage devices. programs are not using the system re¬ The subsets are merged onto the other sources. half of the auxiliary storage devices (2) Contrast with foreground processing. and the process is repeated until all items are in one sorted set. backspace (2) Contrast with unbalanced merge sort. (1) To move back the reading or display position according to a prescribed for¬ band mat. (1) (ISO) A group of tracks on a magnet¬ (2) Contrast with space(4). ic drum or on one side of a magnetic disk. backspace character (BS) (2) In data communication, the frequency (ISO) A format effector that causes the spectrum between two defined limits. print or display position to move one po¬ sition backward along the line without bank producing the printing or display of any See data bank. graphic. bar See type bar. Backus Naur form (BNF) A metalanguage used to specify or de¬ bar printer scribe the syntax of a language in which An impact printer in which the type slugs each symbol, by itself, represents a set of are carried on a type bar. strings of symbols. Synonymous with Backus normal form. base (1) (ISO) In the numeration system com¬ Backus norma! form (BNF) monly used in scientific papers, the Synonym for Backus Naur form. number that is raised to the power denoted by the exponent and then balanced error multiplied by the mantissa to deter¬ (ISO) A set of errors the distribution of mine the real number represented, which has the mean value zero. e.g., the number 6.25 in the expres¬ sion 2.7 x 6.2515 = 42.1875. balanced merge (2) A reference value. An external sort that places strings created (3) A number that is multiplied by itself by an internal sort phase on half of the as many times as indicated by an ex¬ available storage devices and then merges ponent. strings by moving them back and forth (4) Contrast with radix. between an equal number of devices until (5) See complement base, data base, the merging process is complete. floating-point base. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 15

base address (2) In asynchronous transmission, the unit (1) (ISO) A numeric value that is used as of modulation rate corresponding to a reference in the calculation of ad¬ one unit interval per second, i.e., if dresses in the execution of a computer the duration of the unit interval is 20 program. milliseconds, the modulation rate is 50 (2) A given address from which an abso¬ baud. lute address is derived by combination with a relative address. BCD Binary-coded decimal notation. base address register (ISO) A register that holds the base ad¬ beginning-of-tape marker dress. Synonym for base register. (1) (ISO) A marker on a magnetic tape used to indicate the beginning of the base register permissible recording area, e.g., a Synonym for base address register. photo reflective strip, a transparent section of tape.

batch processing (2) Contrast with end-of-tape marker. (1) The processing of data or the accom¬ plishment of jobs accumulated in ad¬ BEL vance in such a manner that each ac¬ The bell character. cumulation thus formed is processed or accomplished in the same run. bell character (BEL) (2) The processing of data accumulated (ISO) A control character that is used over a period of time. when there is a need to call for human (3) Loosely, the execution of computer attention and that may activate alarm or programs serially. other attention devices. (4) Pertaining to the technique of execut¬ ing a set of computer programs such benchmark problem that each is completed before the next (1) A problem used to evaluate the per¬ program of the set is started. formance of hardware or software or (5) Pertaining to the sequential input of both. computer programs or data. (2) A problem used to evaluate the per¬ (6) See remote batch processing, sequen¬ formance of several computers relative tial batch processing. to each other, or a single computer relative to system specifications.

baud (1) A unit of signalling speed equal to bias the number of discrete conditions or (1) (ISO) A systematic deviation of a va¬ signal events per second. For exam¬ lue from a reference value. ple, one baud equals one-half dot cy¬ (2) The amount by which the average of cle per second in Morse code, one bit a set of values departs from a refer¬ per second in a train of binary sig¬ ence value. nals, and one 3-bit value per second (3) See ordering bias. in a train of signals each of which can assume one of eight different bias error states. (ISO) An error due to bias. 16 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

bidirectional flow binary-coded decimal notation (BCD) (ISO) In flowcharting, flow that can occur (ISO) A binary-coded notation in which over the same flowhne in either direction. each of the decimal digits is represented by a binary numeral, e.g., in binary-coded binary decimal notation that uses the weights (1) (ISO) Pertaining to a selection, choice, 8-4-2-1, the number “twenty three” is or condition that has two possible dif¬ represented by 0010 0011 (compare its re¬ ferent values or states. presentation 10111 in the pure binary nu¬ (2) (ISO) Pertaining to a fixed radix nu¬ meration system). Synonymous with meration system having a radix of binary-coded decimal code, binary-coded two. decimal representation, coded decimal no¬ (3) See Chinese binary, column binary, tation. row binary.

binary-coded decimal representation binary arithmetic operation Synonym for binary-coded decimal nota¬ (1) (ISO) An arithmetic operation in tion. which the operands and the result are represented in the pure binary numer¬ binary-coded notation ation system. (ISO) A binary notation in which each of (2) Synonym for dyadic operation. the decimal digits is represented by a bi¬ nary numeral. binary boolean operation (ISO) Deprecated term for dyadic boolean binary digit (BIT) operation. (1) (ISO) In binary notation, either of the characters, 0 or 1. binary card (2 ) (ISO) Synonym for bit. A card containing data in column binary (3) See equivalent-binary-digit factor. or row binary form.

binary element binary cell (ISO) A constituent element of data that ( 1) (ISO) A storage cell that can hold one binary character. takes either of two values or states. The (2) A storage cell of one binary digit term bit, originally the abbreviation for capacity, e.g., a single-bit register. the term binary digit, is misused in the sense of binary element or in the sense of

binary code Shannon. A code that makes use of exactly two dis¬ tinct characters, usually 0 and 1. binary element string (ISO) A string consisting solely of binary

binary-coded decimal code elements. Synonym for binary-coded decimal nota¬ tion. binary notation (1) (ISO) Any notation that uses two dif¬ binary-coded decimal interchange code ferent characters, usually the binary See extended binary-coded decimal inter¬ digits 0 and 1, e.g., the gray code. change code. The gray code is a binary notation AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 17

but not a pure binary numeration sys¬ bind tem. (ISO) To assign a value to a variable; in (2) Fixed-radix notation where the radix particular, to assign a value to a parame¬ is two. For example, in binary nota¬ ter. tion the numeral 110.01 represents the number 1 x 2 squared plus 1 x 2 to binder-hole card the first power plus 1 x 2 to the A card that contains one or more holes minus 2 power, that is, six and a for binding. quarter.

bionics binary number A branch of technology relating the Loosely, a binary numeral. functions, characteristics, and phenomena of living systems to the development of binary numeral mechanical systems. (1) (ISO) A numeral in the pure binary numeration system, e.g., the binary biquinary code numeral 101 is equivalent to the Ro¬ man numeral V. (ISO) A notation in which a decimal digit (2) A binary representation of a number, n is represented by a pair of numerals, a e.g., 101 is a binary numeral and a V being 0 or I, b being 0, 1, 2, 3, or 4, is the equivalent Roman numeral. and 5a + b being equal to n. The two digits are often represented by a series of binary numeration system two binary numerals. (ISO) Synonym for pure binary numera¬

tion system. bistable Pertaining to a device capable of assum¬ binary operation ing either one of two stable states. (ISO) Deprecated term for binary arith¬

metic operation, boolean operation. bistable circuit (1) (ISO) A trigger circuit that has two binary operator stable states. Synonymous with bista¬ Synonym for dyadic operator. ble trigger circuit. (2) Synonym for flip-flop. binary search (ISO) A dichotomizing search in which, bistable trigger circuit at each step of the search, the set of Synonym for bistable circuit. items is partitioned into two equal parts, some appropriate action being taken in bit the case of an odd number of items. (1) (ISO) In the pure binary numeration system, either of the digits 0 and 1. binary symmetric channel (ISO) A channel designed to convey mes¬ Synonymous with binary digit. sages consisting of binary characters and (2) (ISO) Deprecated term for binary ele¬ that has the property that the conditional ment, Shannon. probabilities of changing any one charac¬ (3) See check bit, information bits, parity ter to the other character are equal. bit, redundancy check bit, sign bit. 18 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

bit position block character (ISO) A character position in a word in a See end-of-transmission-block character. binary notation. block diagram

bit string (1) (ISO) A diagram of a system, instru¬ (ISO) A string consisting solely of bits. ment, or computer in which the prin¬ cipal parts are represented by suitably annotated geometrical figures to show blank both the basic functions of the parts A part of a data medium in which no and the functional relationships be¬ characters are recorded. tween them. (2) Contrast with flowchart. blank character A graphic representation of the space block gap character. (ISO) Synonym for interblock gap( 1).

blip block ignore character (ISO) Synonym for document mark. Synonym for block cancel character.

block block length ( 1) (ISO) A string of records, a string of (1) (ISO) The number of records, words, words, or a character string, formed or characters in a block. for technical or logic reasons to be (2) A measure of the size of a block, treated as an entity. usually specified in units such as re¬ (2) A set of things, such as words, cords, words, computer words, or characters, or digits, handled as a characters. unit.

(3) A collection of contiguous records block structure recorded as a unit. Blocks are A hierarchy of program blocks. separated by interblock gaps and each

block may contain one or more re¬ block transfer cords. (ISO) The process, initiated by a single (4) A group of bits, or n-ary digits, trans¬ action, of transferring one or more blocks mitted as a unit. An encoding proce¬ of data. dure is generally applied to the group

of bits or n-ary digits for error-control blowbaek purposes. In micrographics, an enlargement. (5 ) See program block.

BNF block cancel character (1) Backus Naur form. (ISO) A cancel character used to indicate (2) Backus normal form. that the preceding portion of the block, back to the most recently occurring block boolean mark, is to be disregarded. Synonymous Pertaining to the processes used in the al¬ with block ignore character. gebra formulated by George Boole. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 19

boolean add used to establish another version of Synonym for OR. the computer program. (4) (ISO) To use a bootstrap. boolean complementation (5) See also bootstrap loader, initial pro¬ (ISO) Deprecated term for negation. gram loader.

boolean function bootstrap loader (ISO) A switching function in which the (1) (ISO) An input routine in which sim¬ number of possible values of the function ple preset computer operations are and each of its independent variables is used to load instructions which in turn two. cause further instructions to be loaded until the complete computer program Iioolean operation is in storage.

(1) (ISO) Any operation in which each of (2) See also bootstrap, initial program the operands and the result take one loader. of two values. (2) (ISO) An operation that follows the borrow rules of boolean algebra. ( 1) An arithmetically negative carry. (3) See dyadic boolean operation, n-adic (2) See end-around borrow. boolean operation, n-ary boolean oper¬ ation. borrow digit (ISO) A digit that is generated when a difference in a digit place is arithmetically boolean operation table negative and that is transferred for proc¬ (ISO) An operation table in which each essing elsewhere. In a positional represen¬ of the operands and the result take one tation system, a borrow digit is transferred of two values. to the digit place with the next higher weight for processing there. boolean operator (1) (ISO) An operator each of the ope¬ branch rands of which and the result of (1) A set of instructions that are executed which take one of two values. between two successive branch instruc¬ (2) See dyadic operator, monadic opera¬ tions. tor. (2) A direct path joining two nodes of a network or graph. bootstrap (3) Loosely, a conditional jump. (1) (ISO) An existing version, perhaps a (4) (ISO) In the execution of a computer primitive version, of a computer pro¬ program, to select one from a number gram that is used to establish another of alternative sets of instructions. version of the program. (5) To select a branch as in (1). (2) A technique or device designed to (6) (ISO) Deprecated term for jump. bring itself into a desired state by

means of its own action, e.g., a ma¬ branch instruction chine routine whose first few instruc¬ (1) (ISO) An instruction that controls tions are sufficient to bring the rest of branching. Synonymous with decision itself into the computer from an input instruction. device. (3) That part of a computer program 20 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(2) (ISO) Deprecated term for jump in¬ driven circuit from influencing the struction. driving circuit. (3) To allocate and schedule the use of branchpoint buffers. (1) (ISO) A point in a computer program

at which branching occurs, in particu¬ buffering lar the address or the label of an in¬ See anticipatory buffering. struction. (2) A place in a routine where a branch buffer storage is selected. (ISO) A storage device that is used to compensate for differences in the rate of breakpoint flow of data between components or, of (ISO) A place in a computer program, usu¬ an automatic data processing system, for ally specified by an instruction, where its the time of occurrence of events in the execution may be interrupted by external in¬ tervention or by a monitor program. components.

breakpoint halt bug (ISO) A closed loop consisting of a single A mistake or malfunction. jump instruction that effects a jump to it¬ self, often used to achieve a breakpoint. built-in check Synonymous with breakpoint instruction, Synonym for automatic check. dynamic stop. bulk storage breakpoint instruction (ISO) Synonym for mass storage. (ISO) Synonym for breakpoint halt.

burst b-register ( 1) In data communication, a sequence of (ISO) Deprecated term for index register. signals counted as one unit in accord¬ ance with some specific criterion or BS measure. The backspace character. (2) To separate continuous-form paper into discrete sheets. bubble sort ( 3 ) See error burst. An exchange sort in which the sequence of examination of pairs of items is rev¬ bus ersed whenever an exchange is made. Sy¬ One or more conductors used for transmit¬ nonymous with sifting sort. ting signals or power.

buffer ( 1) A routine or storage used to compen¬ business data processing sate for a difference in rate of flow of ( 1) Data processing for business purposes, data, or time of occurrence of events, e.g., recording and summarizing the fi¬ when transferring data from one de¬ nancial transactions of a business. vice to another. (2) (ISO) Synonym for administrative data (2) An isolating circuit used to prevent a processing. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 21

byte ( I) (ISO) A binary character string operated upon as a unit and usually shorter than a computer word. 22 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

calling sequence c (ISO) An arrangement of instructions and in some cases of data also, that is neces¬ calculating punch sary to perform a call. (ISO) A calculator with a card reader and a card punch that reads the data on a CAN punched card, performs some arithmetic The cancel character. operations or logic operations on the data, and punches the results on the same or cancel character (CAN) another punched card. Synonymous with (1) (ISO) A control character used by multiplying punch. some convention to indicate that the data with which it is associated are in calculator error or are to be disregarded. Sy¬ (1) (ISO) A data processor, especially nonymous with ignore character. suitable for performing arithmetical (2) An accuracy control character used to operations, that requires frequent inter¬ indicate that the data with which it is vention by a human operator. associated are in error or are to be (2) A device for carrying out logic and disregarded. arithmetical digital operations of any (3) See block cancel character. kind.

capacitor storage calculus of variations (ISO) A storage device that uses the The theory of maxima and minima of capacitive properties of certain materials. definite integrals whose integrand is a function of the dependent variables, the independent variables, and their deriva¬ capacity tives. See channel capacity, storage capacity.

call card (1) (ISO) The action of bringing a com¬ See aperture card, binary card, binder puter program, a routine, or a subrou¬ hole card, check card, double card, edge tine into effect, usually by specifying coated card, edge-notched card, edge- the entry conditions and jumping to punched card, flash card, header card, an entry point. Hollerith card, laced card, magnetic card, (2) In data communication, the action mark-sensing card, processable scored performed by the calling party, or the card, punch card, punched card, scored operations necessary in making a call, card, short card, source data card, stub or the effective use made of a connec¬ card, trailer card. tion between two stations. (3) (ISO) In computer programming, to card column execute a call. (1) (ISO) A line of punch positions paral¬ (4) To transfer control to a specified lel to the shorter edge of a punch closed subroutine. card. (5) Synonymous with cue. (2) A line of punch positions parallel to (6) See subroutine call. the Y-datum line of a punch card. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 23

card deck them into machine language. Synony¬ (ISO) A group of related punched cards. mous with punched card reader.

card feed card row (ISO) The mechanism that moves punch (1) (ISO) A line of punch positions paral¬ cards from the card hopper to the card lel to the longer edge of a punch track. card. (2) A line of punch positions parallel to card field the X-datum line of a punch card. A specific combination of punch positions, mark sensing positions, or both, on a cards card. See continuous-form cards.

card form card set See printed card form. Cards and forms, bound in a manner that provides multiple copies of source data. card hopper (1) (ISO) The part of a card-processing card stacker device that holds the cards to be (1) (ISO) The part of a card-processing processed and makes them available device that receives the cards after to a card feed mechanism. they have been processed. (2) Contrast with card stacker. (2) Contrast with card hopper.

card image card storage A one-to-one representation of the hole See magnetic card storage. patterns of a punched card, e.g., a matrix in which a one represents a punch and a card track zero represents the absence of a punch. The part of a card-processing device that moves and guides the card through the card jam device. (ISO) A malfunction of a card-processing device in which cards become jammed. carriage See automatic carriage. card punch ( 1) A device that punches holes in a card carriage control tape to represent data. (1) A tape that is used to control vertical (2) (ISO) Deprecated term for keypunch. tabulation of printing positions or dis¬ play positions. card reader (2) A tape that contains line feed control (1) (ISO) A device that reads or senses data for a printing device. the holes in a punched card, trans¬ forming the data from hole patterns carriage return to electrical signals. The operation that prepares for the next (2) An input device that senses hole pat¬ character to be printed or displayed at the terns in a punched card and translates specified first position on the same line. 24 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

carriage return character (CR) cascaded carry (1) (ISO) A format effector that causes (1) (ISO) In parallel addition, a proce¬ the print or display position to move dure in which the addition results in a to the first position on the same line. partial sum numeral and a carry nu¬ (2) A format effector that causes the loca¬ meral which are in turn added; this tion of the printing or display position process is repeated until no carries are to be moved to the first space on the generated. same printing or display line. (2) Contrast with high-speed carry. (3 ) Contrast with new line character. catalog carry An ordered compilation of item descrip¬ ( 1) (ISO) The action of transferring a tions and sufficient information to afford carry digit. access to the items. (2) One or more digits, produced in con¬ nection with an arithmetic operation cathode ray storage on one digit place of two or more nu¬ (ISO) An electrostatic storage that uses a merals in positional notation, that are cathode ray beam for access to data. forwarded to another digit place for processing there. cathode ray tube display (CRT display) (3) The number represented by the digit ( 1) A device that presents data in visual or digits in (2). form by means of controlled electron (4) Most commonly, a digit as defined in beams. (2), that arises when the sum or (2) The data display produced by the de¬ product of two or more digits equals vice as in ( 1). or exceeds the radix of the number representation system. cell (5) Less commonly, a borrow. See binary cell, magnetic cell, storage cell. (6) The command directing that a carry be forwarded. central processing unit (CPU) (7) (ISO) To transfer a carry digit. (ISO) A unit of a computer that includes (8) To forward a carry. circuits controlling the interpretation and (9) See addition without carry, cascaded execution of instructions. Synonymous carry, complete carry, end-around car¬ with central processor, main frame. ry, high-speed carry, partial carry, standing-on-nines carry. central processor Synonym for central processing unit. carry digit (ISO) A digit that is generated when a chad sum or a product in a digit place exceeds ( 1) (ISO) The material separated from a the largest number that can be represent¬ punched tape or a punched card when ed in that digit place and that is trans¬ forming a hole. ferred for processing elsewhere. In a po¬ (2) Synonymous with chip. sitional representation system, a carry digit is transferred to the digit place with the chadless tape next higher weight for processing there. (ISO) Punched tape that has been AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 25

punched in such a way that chad is not sent, e.g., data channel, output chan¬ formed. nel. (2) The portion of a storage medium that chain is accessible to a given reading or ( 1 ) See Markov chain. writing station, e.g., track, band. (2) See also chained list. (3) (ISO) In information theory, that part of a communication system that con¬ nects the message source with the chain code message sink. Mathematically, this An arrangement in a cylic sequence of part can be characterized by the set some or all of the possible different n-bit of conditional probabilities of occur¬ words, in which adjacent words are relat¬ rence of all the possible messages re¬ ed such that each is derivable from its ceived at the message sink when a neighbor by displacing the bits one digit given message emanates from the position to the left, or right, dropping the message source. leading bit and inserting a bit at the end. (4) In data communication, a means of The value of the inserted bit needs only one way transmission. Contrast with to meet the requirement that a word must circuit. not recur before the cycle is complete, (5) See binary symmetric channel, input e.g., 000 001 010 101 011 111 110 100 channel, input-output channel, output 000 ... channel.

chained list channel capacity (ISO) A list in which the items may be (ISO) The measure of the ability of a dispersed but in which each item contains given channel subject to specific con¬ an identifier for locating the next item. straints to transmit messages from a speci¬ fied message source expressed either as chaining search the maximum possible mean transinforma- (ISO) A search in which each item con¬ tains means for locating the next item to tion content per character, or as the max¬ be considered in the search. imum possible average transinformation rate.

chain printer (ISO) An impact printer in which the chapter type slugs are carried by the links of a (ISO) Deprecated term for segment. revolving chain. character change character (1) (ISO) A member of a set of elements See font change character. upon which agreement has been reached and that is used for the or¬ change dump ganization, control, or representation (ISO) A selective dump of those storage of data. Characters may be letters, locations whose contents have changed. digits, punctuation marks, or other symbols, often represented in the form channel of a spatial arrangement of adjacent (1) A path along which signals can be or connected strokes or in the form of 26 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

other physical conditions in data character boundary media. In character recognition, the largest rectan¬ (2) A letter, digit, or other symbol that is gle, with a side parallel to the document used as part of the organization, con¬ reference edge, each of whose sides is trol, or representation of data. A tangential to a given character outline. character is often in the form of a

spatial arrangement of adjacent or character check connected strokes. A check that verifies the observance of (3) See accuracy control character, ac¬ rules for the formation of characters. knowledge character, alphanumeric character set, alphanumeric character character display device subset, backspace character, bell (ISO) A display device that gives a re¬ character, blank character, block can¬ presentation of data only in the form of cel character, cancel character, carriage cnaracters. Synonymous with read-out de¬ return character, check character, code vice. extension character, control character, cyclic redundancy check character, data link escape character, delete character fill character, device control character, (ISO) To insert as often as necessary into end-of-medium character, end-of-text a storage medium the representation of a character, end-of-transmission-block specified character that does not itself character, end-of-transmission charac¬ convey data but may delete unwanted ter, enquiry charcter, erase character, data. escape character, font change charac¬

ter, form feed character, gap charac¬ character information rate ter, graphic character, group separator (ISO) Synonym for character mean character, horizontal tabulation charac¬ entropy. ter, illegal character, line feed charac¬ ter, negative acknowledge character, characteristic new line character, null character, print (1) (ISO) In a floating-point representa¬ control character, redundancy check tion, the numeral that represents the character, shift-in character, shift-out exponent. character, sign character, space charac¬ (2) (ISO) The integer part, which may be ter, special character, start-of-heading positive or negative, of the representa¬ character, start-of-text character, substi¬ tion of a logarithm. tute character, synchronous idle (3) Contrast with mantissa. character, transmission control charac¬ ter, vertical tabulation character. character mean entropy

eharacter-at-a-tinie printer (ISO) In information theory, the mean per Synonym for character printer. character of the entropy for all possible messages from a stationary message character average information content source; in mathematical notation, if H is (ISO) Synonym for character mean the entropy of the set of all sequences of entropy. m characters from the source, then this AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 27

mean per character H' equals: Synonymous with character-at-a-time printer. (2) Contrast with line printer, page print¬ er. H,= lim Hm m rr, character reader (ISO) An input unit that performs charac¬ The mean entropy per character may be ter recognition. expressed in a unit such as a Shannon per character. Synonymous with character character recognition average information content, character in¬ (1) (ISO) The identification of characters formation rate, character mean information by automatic means. content. (2) See magnetic ink character recognition, optical character recognition, pattern character mean information content recognition. (ISO) Synonym for character mean

entropy. character set (1) (ISO) A finite set of different charac¬ character mean transformation content ters upon which agreement has been (ISO) In information theory, the mean per reached and that is considered com¬ character of the mean transinformation plete for some purpose, e.g., each of content for all possible messages from a the character sets in ISO Recommen¬ stationary message source; in mathematical dation R646 “6- and 7-bit coded

notation, if T m is the mean transinforma- character sets for information process¬ tion content for all pairs of corresponding ing interchange”. input and output sequences of m charac¬ (2) An ordered set of unique representa¬ ters, then this mean per character T' tions called characters, e.g., the 26 let¬ equals: ters of the English alphabet, boolean 0 and 1, the set of symbols in the Morse code, and the 128 ASCII characters. 7-'= lim Tr m ~>°° m (3) See alphabetic character set, alphabetic coded character set, alphanumeric character set, alphanumeric coded character set, coded character set, nu¬ The mean transinformation content per meric character set, numeric coded character may be expressed in a unit such character set. as Shannon per character. character spacing reference line character outline In character recognition, a vertical line The graphic pattern established by the that is used to evaluate the horizontal stroke edges of a character. spacing of characters. It may be a line that equally divides the distance between character printer the sides of a character boundary or that (1) (ISO) A device that prints a single coincides with the centerline of a vertical character at a time, e.g., a typewriter. stroke. 28 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

character string other computer programs or sets of data (ISO) A string consisting solely of charac¬ for mistakes of syntax. ters. checkout character subset Synonym for debug. (1) (ISO) A selection of characters from a character set, comprising all characters checkpoint that have a specified common feature, (ISO) A place in a computer program at e.g., in each of the character sets of which a check is made or at which a ISO Recommendation R646 “6- and recording of data is made for restart pur¬ 7-bit coded character sets for informa¬ poses. tion processing interchange”, the digits 0 to 9 may constitute a character sub¬ Chinese binary set. Synonym for column binary. (2) See alphabetic character subset, al¬

phanumeric character subset, numeric chip character subset. (1) A minute piece of semiconductive material used in the manufacture of check electronic components. (1) A process for determining accuracy. (2) An integrated circuit on a piece of (2) See automatic check, character check, semiconductive material. duplication check, echo check, margin¬ (3) In micrographics, a piece of microfilm al check, mathematical check, parity smaller than a microfiche containing check, programmed check, residue microimages and coded identification. check, selection check, sight check, (4) (ISO) Synonym for chad. summation check, transfer check.

cine-oriented image check bit (1) In micrographics, an image appearing (1) A binary check digit, e.g., a parity bit. on a roll of microfilm in such a man¬ (2) See redundancy check bit. ner that the top edge of the image is perpendicular to the long edge of the check card film. ( 1) A punched card suitable for use as a (2) Contrast with comic-strip oriented im¬ bank check. age. (2) A punch card used for checking.

circuit check character (1) In data communication, a means of A character used for the purpose of per¬ two-way communication between two forming a check. data terminal installations. (2) Contrast with channel. check digit (3) See bistable circuit, combinational cir¬ A digit used for the purpose of perform¬ cuit, monostable circuit, sequential cir¬ ing a check. cuit, trigger circuit.

checking program circular shift (ISO) A computer program that examines Synonym for end-around shift. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 29

circulating register ates periodic signals used for synchroniza¬ A shift register in which data moved out tion. Synonymous with clock pulse. of one end of the register are reentered into the other end as in a closed loop. clock track (ISO) A track on which a pattern of sig¬ circulating storage nals is recorded to provide a timing refer¬ Dynamic storage involving a closed loop. ence. Synonymous with cyclic storage. closed loop clear (ISO) A loop that has no exit and whose (1) (ISO) To put one or more storage lo¬ execution can be interrupted only by inter¬ cations or registers into a prescribed vention from outside the computer pro¬ state, usually that denoting zero. gram in which the loop is included. (2) (ISO) To cause one or more storage locations to be in a prescribed state, closed shop usually that corresponding to zero or ( 1) Pertaining to the operation of a com¬ that corresponding to the space puter facility in which most productive character. problem programming is performed by a group of programming specialists clear area rather than the problem originators. In character recognition, a specified area The use of the computer itself may that is to be kept free of printing or any also be described as closed shop if other markings not related to machine full time trained operators, rather than reading. user/programmers serve as the opera¬ tors. clock (2) Contrast with open shop. (1) (ISO) A device that generates periodic signals from which synchronism may closed subroutine be maintained. (1) (ISO) A subroutine of which one re¬ (2) A device that measures and indicates plica suffices for the subroutine to be time. linked by calling sequences for use at (3) A register whose content changes at more than one place in a computer regular intervals in such a way as to program. measure time. (2) Contrast with open subroutine. (4) (ISO) Deprecated term for timer. coalesce clock pulse (1) (ISO) To combine two or more sets (1) A synchronization signal provided by of items into one set of any form. a clock. (2) To combine two or more files into (2) (ISO) Synonym for clock signal. one file.

clock register coated card (ISO) Synonym for timer. See edge-coated card.

clock signal COBOL(common business oriented (ISO) The output of a device that gener¬ language) 30 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

A programming language designed for characters of the set and their coded business data processing. representations. Synonymous with code. code (2) See alphabetic coded character set, al¬ (1) (ISO) A set of unambiguous rules phanumeric coded character set, nu¬ specifying the manner in which data meric coded character set. may be represented in a discrete form. Synonymous with coding scheme. coded decimal notation (2) A set of items, such as abbreviations, Synonym for binary-coded decimal nota¬ representing the members of another tion. set.

(3) (ISO) To represent data or a comput¬ coded representation er program in a symbolic form that (ISO) The representation of an item of can be accepted by a data processor. data established by a code or the re¬ (4) To write a routine. presentation of a character established by (5) (ISO) Deprecated term for coded re¬ a coded character set, e.g., “ORY” as the presentation, code set. representation of Paris (Orly) in the code (6) (ISO) Synonym for coded representa¬ for 3-letter identification for airports; the tion. seven binary elements representing the (7) Synonym for coded character set. delete character in the ISO 7-bit coded (8) See alphabetic code, alphanumeric character set. Synonymous with code, code, binary code, biquinary code, code element, code value. chain code, computer instruction code, data code, error correcting code, error code element detecting code, excess-three code, gray code, hamming code, interpretive code, Synonym for coded representation. minimum distance code, numeric code, object code, operation code, perforated code extension character tape code, pseudo code, retrieval code, (ISO) Any control character used to indi¬ return code, skeletal code, two-out- cate that one or more of the succeeding of-five code. coded representations are to be interpreted according to a different code or according

code area to a different coded character set. In micrographics, a part of the film frame reserved for retrieval code. code line index In micrographics, a visual index consisting

code converter of an optical pattern of clear and opaque (ISO) A data converter that changes the bars parallel to the long edge of the roll representation of data, using one code in microfilm and located between images. the place of another or one coded charac¬ ter set in the place of another. code position (ISO) Synonym for punch position. coded character set (1) (ISO) A set of unambiguous rules that coder establish a character set and the one- A person who writes but does not usually to-one relationships between the design computer programs. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 31

code set column (ISO) The complete set of representations (1) A vertical arrangement of characters defined by a code, or by a coded charac¬ or other expressions. ter set, e.g., all of the three-letter inter¬ (2) Contrast with row. national identifications for airports. (3) See card column, mark-sensing co¬ lumn, punch column. code value (ISO) Synonym for coded representation. column binary (1) Pertaining to the binary representation coding of data on cards in which the weights See absolute coding, relative coding, of punch positions are assigned along straight line coding, symbolic coding. card columns. For example, each co¬ lumn in a 12-row card may be used

coding scheme to represent 12 consecutive bits. Sy¬ Synonym for code (1). nonymous with Chinese binary. (2) Contrast with row binary.

collate (1) (ISO) To alter the arrangement of a column split set of items from two or more or¬ The capability of a punch card device to dered subsets to one or more other read or punch two parts of a card column subsets each containing a number of independently. items, commonly one, from each of the original subsets in a specified or¬ COM der that is not necessarily the order of (1) Computer output microfilm. any of the original subsets. (2) Computer output microfilmer. (2) See also merge. combination collating sequence (1) (ISO) A given number of different (1) (ISO) A specified arrangement used in elements selected from a set without sequencing. Synonymous with se¬ regard to the order in which the quence. selected elements are arranged. (2) An ordering assigned to a set of items (2) Contrast with permutation. such that any two sets in that as¬ (3) See forbidden combination. signed order can be collated. (3) (ISO) Deprecated term for order (1). combinational circuit (ISO) A logic device whose output values, collator at any given instant, depend only upon A device that collates, merges, or matches the input values at that time. A combi¬ sets of punched cards or other documents. national circuit is a special case of a se¬ quential circuit that does not have a stor¬ color age capability. Synonymous with com¬ In optical character recognition, the spec¬ binatorial circuit. tral appearance of the image dependent upon the spectral reflectance of the image, combinational logic element the spectral response of the observer, and (1) A device having at least one output the spectral composition of incident light. channel and zero or more input chan- 32 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

nels, all characterized by discrete communication control character states, such that at any instant the (ISO) Synonym for transmission control state of each output channel is com¬ character. pletely determined by the states of the input channels at the same instant. communication theory (2) Contrast with sequential logic element. (1) (ISO) The mathematical discipline dealing with the probabilistic features combinatoriai circuit of the transmission of data in the pre¬ Synonym for combinational circuit. sence of noise. (2) (ISO) Deprecated term for information combined head theory. (ISO) Synonym for read/write head. comparator comic-strip oriented image (1) (ISO) A device that compares two (1) In micrographics, an image appearing items of data and indicates the result on roll microfilm in such a manner of that comparison. that the top edge of the image is par¬ (2) A device for determining the dis¬ allel to the long edge of the film. similarity of two items such as two (2) Contrast with cine-oriented image. pulse patterns or words.

command compare (1) A control signal. (ISO) To examine two items to discover (2) Loosely, an instruction. their relative magnitudes, their relative po¬ (3) Loosely, a mathematical or logic oper¬ sitions in an order or in a sequence, or ator. whether they are identical in given charac¬ (4) Deprecated term for instruction. teristics.

command language comparison A source language consisting primarily of ( 1) The process of examining two or procedural operators, each capable of in¬ more items for identity, similarity, voking a function to be executed. equality, relative magnitude, or for or¬ der in a sequence. comment (2 ) See logical comparison. (ISO) A description, reference, or explana¬

tion, added to or interspersed among the compile statements of the source language, that (1) (ISO) To translate a computer pro¬ has no effect in the target language. Sy¬ gram expressed in a problem-oriented nonymous with computer program annota¬ language into a computer-oriented lan¬ tion. guage. (2) To prepare a machine language pro¬ common field gram from a computer program writ¬ A Held that can be accessed by two or ten in another programming language more independent routines. by making use of the overall logic structure of the program, or generat¬ communication ing more than one computer instruc¬ See data communication. tion for each symbolic statement, or AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 33

both, as well as performing the func¬ specified number by subtracting it tion of an assembler. from a second specified number. For example, in radix notation, the second compile-and-go specified number may be a given An operating technique in which there are power of the radix or one less than a no stops between the compiling, loading, given power of the radix. The nega¬ and execution of a computer program. tive of a number is often represented by its complement. compile duration (3) See diminished radix complement, (ISO) Synonym for compiling time. nines complement, ones complement, radix complement, tens complement, compile phase twos complement. (ISO) Of a run, the logical subdivision

that includes the execution of the compil¬ complementary operation er. Synonymous with compiling phase. (ISO) Of a boolean operation, another boolean operation whose result, when it is compiler performed on the same operands as the (ISO) A computer program used to com¬ first boolean operation, is the negation of pile. Synonymous with compiling pro¬ tne result of the first boolean operation. gram.

complementary operator compiler generator The logic operator whose result is the (ISO) A translator or an interpreter that NOT of a given logic operator. is used to construct compilers.

complement base compiling phase (ISO) In a fixed-radix numeration system. (ISO) Synonym for compile phase. the specified number whose digital re¬ presentation contains the digits from which compiling program the corresponding digits of the given num¬ (ISO) Synonym for compiler. ber are subtracted in obtaining a comple¬ ment of the given number. compiling time (ISO) The elapsed time taken for the exe¬ complementer cution of a compiler. Synonymous with (ISO) A device whose output data are a compile duration. representation of the complement of the

complement number represented by its input data. (1) (ISO) In a fixed-radix numeration sys¬ tem, a numeral that can be derived complement-on-nine from a given numeral by operations (ISO) Synonym for nines complement. that include subtracting each digit of the digital representation of the given complement-on-one number from the corresponding digit (ISO) Synonym for ones complement. of the digital representation of a specified number. complement-on-ten (2) A number that can be derived from a (ISO) Synonym for tens complement. 34 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

complement-on-two computer assisted management (ISO) Synonym for twos complement. (ISO) Management performed with the aid of automatic data processing. complete carry (1) (ISO) In parallel addition, a proce¬ computer-dependent language dure in which each of the carries is Synonym for assembly language. immediately transferred. (2) Contrast with partial carry. computer graphics (ISO) That branch of science and tech¬ complex number nology concerned with methods and tech¬ (ISO) A number consisting of an ordered niques for converting any form of infor¬ pair of real numbers, expressible in the mation to or from graphic display via form a+bp where a and b are real num¬ computers. bers and i squared equals minus one.

computer instruction component (ISO) An instruction that can be recog¬ See solid state component. nized by the central processing unit of the computer for which it is designed. computational stability Synonymous with machine instruction. The degree to which a computational process remains valid when subjected to computer instruction code effects such as errors, mistakes, or mal¬ (ISO) A code used to represent the in¬ functions. structions in an instruction set. Synony¬ mous with machine code. computer (1) (ISO) A data processor that can per¬ computer instruction set form substantial computation, including A complete set of the operators of the in¬ numerous arithmetic operations or log¬ structions of a computer together with a ic operations, without intervention by description of the types of meanings that a human operator during a run. can be attributed to their operands. (2) See analog computer, arbitrary se¬ quence computer, asynchronous com¬ Synonymous with machine instruction puter, consecutive sequence computer, set. digital computer, general purpose com¬ puter, hybrid computer, incremental computer language computer, parallel computer, self- (1) (ISO) A computer-oriented language adapting computer, self-organizing whose instructions consist only of com¬ computer, sequential computer, serial puter instructions. Synonymous with computer, simultaneous computer, spe¬ machine language. cial purpose computer, stored program (2) (ISO) Deprecated term for computer- computer, synchronous computer. oriented language.

computer architecture computer network The specification of the relationships be¬ A complex consisting of two or more in¬ tween the parts of a computer system. terconnected computers. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 35

computer operation computer time One of the elementary operations which a In simulation, the time required to process computer is designed to perform. Synony¬ the data that represents a process or that mous with machine operation. represents a pan of a process.

computer-oriented language computer word (1) (ISO) A programming language that (1) (ISO) A word stored in one computer location and capable of being treated reflects the structure of a given com¬ as a unit. Synonymous with fullword, puter or that of a given class of com¬ machine word. puters. (2) See also halfword. (2) A programming language whose words and syntax are designed for use on a concurrent specific class of computers. Synony¬ (1) (ISO) Pertaining to the occurrence of mous with machine-oriented language. two or more activities within a given (3) See also computer language. interval of time. (2) Contrast with simultaneous. computer output microfilm (COM) (3) See also consecutive, sequential. (1) (ISO) Microfilm that contains data that is received directly from concurrent operation computer-generated signals. A mode of operation that includes the (2) To place computer-generated data on performance of two or more operations microfilm. within a given interval of time.

computer output microfilmer (COM) condition A recording device that produces comput¬ See restart condition. er output microfilm. conditional branch instruction

computer program (ISO) Deprecated term for conditional jump instruction. (ISO) A program expressed in a form suitable for execution by a computer. conditional control transfer instruction (ISO) Deprecated term for conditional computer program annotation jump instruction. (ISO) Synonym for comment.

conditional entropy computer program origin (ISO) In information theory, the mean of The address assigned to the initial storage the measure of information conveyed by location of a computer program in main the occurrence of any one of a finite set storage. of mutually exclusive and jointly exhaus¬ tive events of definite conditional proba¬ computer simulator bilities, given the occurrence of events of (ISO) A computer program that translates another set of mutually exclusive events; computer programs prepared for a com¬ in mathematical notation, this means puter of one model for execution on a H(x jy) for a set of events x. xn which computer of a different model. are dependent on the occurrence of events 36 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

from another set y,.ym with joint proba¬ conditional jump instruction bilities plx^yp of the occurrence of both (ISO) An instruction that specifies a con¬ events xi(y. equals the mathematical expec¬ ditional jump and the conditions that tation of the conditional information con¬ have to be satisfied for the conditional tent I(x, (yj ) of all pairs of events: jump to occur. hn j=m H(x \y)= P(Xj.Vj)I(Xj I Vj) = conditional statement hi j=1 A statement used to express an assign¬ i=n j=m ment or branch, based on specified E E 'os-^TTy criteria, e.g., an IF-THEN statement. hi j=1 1 1

Synonymous with average conditional in¬ conditional transfer instruction formation content, mean conditional infor¬ (ISO) Deprecated term for conditional mation content. jump instruction, jump instruction.

conditional implication operation conditions (ISO) Synonym for implication. See entry conditions.

conditional information content conjunction (ISO) In information theory, a measure of (1) (ISO) The boolean operation whose information conveyed by the occurrence of result has the boolean value 1 if and an event of a definite conditional proba¬ only if each operand has the boolean bility, given the occurrence of another value 1. Synonymous with AND op¬ event; in mathematical notation, this eration, intersection. measure I(x; (y^) for an event from the set (2) Contrast with nonconjunction. x, .xn, that is dependent on the occur¬

rence of another event from the set connector y, .ym, equals the logarithm of the recip¬ (1) (ISO) A flowchart symbol that repre¬ rocal of the conditional probability sents a break in a flowline, the same p(*i bj) of the occurrence of the event x; flowline being continued elsewhere. given the occurrence of the event y. (2) See inconnector, outconnector.

consecutive (1) (ISO) Pertaining to the occurrence of two sequential events without the in¬ _1_ I(x.\y.) = log tervention of any other such event. P(Xj\yj) (2) Contrast with sequential. (3) See also concurrent, simultaneous.

consecutive operation Synonym for sequential operation.

conditional jump consecutive sequence computer (ISO) A jump that takes place only when (ISO) A computer in which instructions the instruction that specifies it is executed are executed in an implicitly defined se¬ and specified conditions are satisfied. quence unless a jump instruction specifies AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 37

the storage location of the next instruction trol character may be recorded for use to be executed. in a subsequent action. A control character is not a graphic character, console but may have a graphic representation (1) A part of a computer used for com¬ in some circumstances. munication between the operator or (2) See accuracy control character, device maintenance engineer and the comput¬ control character, print control charac¬ er. ter, transmission control character. (2) See operator console. control counter constant (ISO) Synonym for instruction address See figurative constant. register.

content control engineering See character mean transinformation con¬ See automatic control engineering. tent, conditional information content, deci¬ sion content, information content, joint in¬ control function formation content, mean transinformation (ISO) Synonym for control operation. content, transinformation content. control hole content-addressed storage (ISO) Synonym for designation hole. Synonym for associative storage. control instruction register continuous-form cards (ISO) Deprecated term for instruction ad¬ Special cards attached together in contin¬ dress register. uous strips to facilitate printing. They can be separated into individual punched control language cards. See job control language.

contrast controller (1) In optical character recognition, the See input-output controller. differences between color or shading of the printed material on a document control operation and the background on which it is (1) (ISO) An action that affects the printed. recording, processing, transmission or (2) See print contrast ratio. interpretation of data, e.g., starting or stopping a process, carriage return, control font change, rewind and end of trans¬ See loop control, numerical control, proc¬ mission. ess control, real-time control, sequential (2) (ISO) Synonymous with control func¬ control. tion.

control character control panel (1) (ISO) A character whose occurrence in (1) A part of a computer console that a particular context initiates, modifies, contains manual controls. or stops a control operation. A con¬ (2) Synonym for plugboard. 38 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(3) See operator control panel. convex programming (1) (ISO) In operations research, a par¬ control program ticular case of nonlinear programming A computer program designed to schedule in which the function to be maximized and supervise the execution of all the pro¬ or minimized and the constraints are grams, routines, and subroutines of a com¬ appropriately convex or concave func¬ puting system. tions of the controllable variables. (2) Contrast with dynamic programming, integer programming, linear program¬ control punch ming, mathematical programming, (ISO) Synonym for designation hole. nonlinear programming, quadratic pro¬ gramming. control register (ISO) Deprecated term for instruction ad¬ copy dress register. (ISO) To read data from a source, leav¬ ing the source data unchanged, and to control tape write the same data elsewhere in a physi¬ See carriage control tape. cal form that may differ from that of the source, e.g., to copy a deck of punched control unit cards onto magnetic tape. The degree of See instruction control unit, main control editing that may be carried out at the unit, peripheral control unit. same time depends upon the circumstances in which the copying is performed. Cer¬ control variable tain synonyms for “to copy” are used in See loop control variable. certain contexts depending on the source and the destination of the data, as shown conversational mode in the following table: A mode of operation of a data processing system in which a sequence of alternating entries between a user and the system takes place in a manner similar to a con¬ versation between two persons.

Source

convert External Storage Internal A or Input Storage Register (1) (ISO) To change the representation of To read To load To load A Register

data from one form to another, with¬ c To read To move To store Internal o ® out changing the information they Storage c convey, e.g., radix conversion; code To transmit External 1 or to read To write To write Storage or conversion; conversion from punched or to write Output cards to magnetic tape; analog to digital conversion. (2) Synonymous with transform. (3) See also copy, duplicate.

converter core See code converter, data converter. (1) (ISO) Deprecated term for tape spool. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 39

(2) See magnetic core, multi-aperture core, CRT display switch core. Cathode ray tube display.

core storage cryogenics (1) A magnetic storage in which the data The study and use of devices utilizing medium consists of magnetic cores. properties of materials near absolute zero (2) See magnetic core storage. in temperature.

corrective maintenance cryogenic storage (1) Maintenance specifically intended to (ISO) A storage device that uses the su¬ eliminate an existing fault. perconductive and magnetic properties of certain materials at very low temperatures. (2) Contrast with preventive maintenance.

corrective maintenance time cryotron A device that makes use of the effects of Time, either scheduled or unscheduled, low temperatures on conductive materials used to perform corrective maintenance. such that small magnetic field changes can control large current changes. counter (1) (ISO) A device whose state represents cue a number and that, on receipt of an Synonym for call. appropriate signal, causes the number represented to be increased by unity curtate or by an arbitrary constant; the device (1) A group of adjacent card rows. is usually capable of bringing the (2) See lower curtate, upper curtate. number represented to a specified va¬ lue, e.g., zero. curve follower (2) See instruction counter, modulo-n (ISO) An input unit that reads data counter, reversible counter. represented by a curve.

CPU cybernetics Central processing unit. (ISO) The branch of learning that brings together theories and studies on communi¬ CR cation and control in living organisms and (1) An abbreviation denoting a credit in machines. symbol in the amount field.

(2) The carriage return character. cycle (1) An interval of space or time in which CRC one set of events or phenomena is The cyclic redundancy check character. completed. (2) Any set of operations that is repeated crosstalk regularly in the same sequence. The The unwanted energy transferred from operations may be subject to varia¬ one circuit, called the disturbing circuit, to tions on each repetition. another circuit, called the disturbed circuit. (3) See search cycle. 40 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

cycle time cyclic shift (1) (ISO) The minimum time interval be¬ Synonym for end-around shift. tween the starts of successive read/ write cycles of a magnetic core stor- age. (2) See read cycle time, write cycle time.

cyclic redundancy check character (CRC) A character used in a modified cyclic cyclic storage code for error detection and correction. Synonym for circulating storage. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 41

D data code (1) A structured set of characters used to represent data items, e.g., the codes data 01, 02, ..., 12 may be used to repre¬ (1) (ISO) A representation of facts, con¬ sent the months January, February, ..., cepts, or instructions in a formalized December of the data element months manner suitable for communication, of the year. interpretation, or processing by hu¬ (2) (ISO) In data communication, a set of mans or by automatic means. rules and conventions according to (2) Any representations such as characters which the signals representing data or analog quantities to which meaning should be formed, transmitted, re¬ is or might be assigned. ceived and processed. (3) See alphanumeric data, analog data, (3) (ISO) Deprecated term for code set. digital data, discrete data, input data, numeric data, output data. data collection station (ISO) Synonym for data input station. data attribute

A characteristic of a unit of data such as data communication length, value, or method of representation. (1) The transmission and reception of data. data bank (2) The transmission, reception, and vali¬ (1) (ISO) A set of libraries of data. dation of data. (2) A comprehensive collection of libraries

of data. For example, one line of an data converter invoice may form an item, a complete (ISO) A device whose purpose is to con¬ invoice may form a record, a com¬ vert data. plete set of such records may form a

file, the collection of inventory control data definition Files may form a library, and the li¬ A program statement that describes the braries used by an organization are features of, specifies relationships of, or known as its data bank. establishes context of data.

data base data flowchart (1) (ISO) A set of data, part or the (ISO) A flowchart that represents the path whole of another set of data, and of data in the solving of a problem, and consisting of at least one file, that is that defines the major phases of the proc¬ sufficient for a given purpose or for a essing as well as the various data media given data processing system. used. Synonymous with data flow dia¬ (2) A collection of data fundamental to a gram. system. (3) A collection of data fundamental to data flow diagram an enterprise. (ISO) Synonym for data flowchart.

data card data hierarchy See source data card. A data structure consisting of sets and 42 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

subsets such that every subset of a set is data name of lower rank than the data of the set. (ISO) A character or group of characters used to identify an item of data. data input station

(ISO) A user terminal primarily for the data processing insertion of data into a data processing (1) (ISO) The execution of a systematic system. Synonymous with data collection sequence of operations performed station. upon data, e.g., handling, merging, sorting, computing. Synonymous with data library information processing. (ISO) A collection of related files, e.g., in (2) See administrative data processing, stock control, a collection of inventory automatic data processing, business control files. data processing, electronic data proc¬ essing, integrated data processing. data link The physical means of connecting one lo¬ data processing system cation to another for the purpose of trans¬ (ISO) A collection of methods, procedures, mitting and receiving data. or techniques united by regulated interac¬ tion to form an organized whole. data link escape character (DLE) (ISO) A transmission control character that changes the meamng of a limited data processor number of contiguously following charac¬ (ISO) A device capable of performing ters or coded representations and that is data processing, such as a desk calculator, used exclusively to provide supplementary a punched card machine, or a computer. transmission control characters. Synonymous with processor! 1 )•

data logging data reduction The recording of data about events that The transformation of raw data into a occur in time sequence. more useful form, e.g., smoothing to reduce noise. data management (1) The function of controlling the acqui¬ data signalling rate sition, analysis, storage, retrieval, and In data communication, the data transmis¬ distribution of data. sion capacity of a set of parallel channels. (2) In an operating system, the computer The data signalling rate is expressed in programs that provide access to data, bits per second. perform or monitor storage of data, and control input-output devices. data sink data medium (1) In data communication, a device capa¬ (1) (ISO) The material in or on which a ble of accepting data signals from a specific physical variable may repre¬ transmission device. It may also sent data. check these signals and originate error (2) (ISO) The physical quantity which control signals. may be varied to represent data. (2) Contrast with data source. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 43

data source decimal notation (1) In data communication, a device capa¬ (1) (ISO) A notation that uses ten differ¬ ble of originating data signals for a ent characters, usually the decimal di¬ transmission device. It may also ac¬ gits, e.g., the character string cept error control signals. 196912312359, construed to represent (2) Contrast with data sink. the date and time one minute before the start of the year 1970; the re¬ data terminal equipment presentation used in the Universal A data source, a data sink, or both. Decimal Classification (UDC). These examples use decimal notation but data transmission neither satisfies the definition of the Synonym for transmission. decimal numeration system. (2) Contrast with decimal numeration sys¬ datum line tem. See X-datum line, Y-datum line. decimal numeral DC1, DC2, DC3, DC4 A numeral in the decimal numeration sys¬ Device control characters. tem.

DDA decimal numeration system Digital differential analyzer. (1) (ISO) The fixed radix numeration sys¬ tem that uses the decimal digits and deblock the radix ten and in which the lowest To separate the parts of blocks, e.g., to integral weight is 1, e.g., in this nu¬ select records from a block. meration system, the numeral 576.2 represents the number: 5 x 102 + 7 x debug 10' + 6 x 10° + 2 x 10-'. (ISO) To detect, to trace, and to elimi¬ (2) Contrast with decimal notation. nate mistakes in computer programs or in other software. Synonymous with check¬ decimal point out. (ISO) The radix point in the decimal nu¬ meration system. The decimal point may decimal be represented, according to various con¬ (1) (ISO) Pertaining to a selection, choice, ventions, by a comma, by a period, or by or condition that has ten possible dif¬ a point at the mid-height of the digits. ferent values or states. (2) (ISO) Pertaining to a fixed-radix nu¬ decision meration system having a radix of ten. See leading decision, trailing decision. Synonymous with denary. (3) See binary-coded decimal notation. decision content (ISO) In information theory, a logarithmic decimal digit measure of the number of decisions need¬ (ISO) In decimal notation, or in the deci¬ ed to select a given event among a finite mal numeration system, one of the digits number of mutually exclusive events; in 0 to 9. mathematical notation, this measure is: 44 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

decoder (1) (ISO) A device that decodes data. (2) (ISO) A device that has a number of 0 ='°Sn u input lines of which any number may carry signals and a number of output lines of which not more than one may where n is the number of events. In in¬ carry a signal, there being a one- formation theory, the term event is to be to-one correspondence between the understood as used in the theory of outputs and the combinations of the probability. For instance, an event may input signals. be the presence of a given element of a (3) Contrast with encoder. set, the occurrence of a specified character (4) See operation decoder. or of a specified word in a given position of a message. decollate To separate the plies of a multipart form decision instruction or paper stock. Synonymous with de¬ (1) (ISO) Deprecated term for discrimina¬ tion instruction. leave. (2) (ISO) Synonym for branch instruction. default option

decision table An implicit option that is assumed when (1) (ISO) A table of all contingencies that no option is explicitly stated. are to be considered in the description of a problem together with the actions deferred addressing to be taken. (ISO) A method of addressing in which (2) A presentation in either matrix or one indirect address is replaced by anoth¬ tabular form of a set of conditions er to which it refers a predetermined and their corresponding actions. number of times or until the process is terminated by an indicator. deck See card deck. deferred maintenance Maintenance specifically intended to elimi¬ declaration nate an existing fault, which did not pre¬ (ISO) In a programming language, a vent continued successful operation of the meaningful expression that affects the in¬ device or computer program. terpretation of other expressions in that language. Synonymous with directive. deferred maintenance time

declarative Time, usually scheduled, used to perform (ISO) Deprecated term for declaration. deferred maintenance.

decode definition (1) (ISO) To convert data by reversing See data definition, macro definition. the effect of some previous encoding. (2) To interpret a code. DEL (3) Contrast with encode. The delete character. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 45

■

delay denary The amount of time by which an event is (ISO) Synonym for decimal!2). retarded. density delay line See packing density, recording density. (1) (ISO) A line or network designed to introduce a desired delay in the trans¬ descriptor mission of a signal usually without In information retrieval, a word used to appreciable distortion. categorize or index information. Synony¬ (2) A sequential logic element with one mous with keyword. input channel and in which an output channel state at any one instant, T, is designation hole the same as the input channel state at (ISO) A hole punched in a punch card to the instant T-N, where N is a con¬ indicate the nature of the data on the stant interval of time for a given out¬ card or the functions that a machine is to put channel, i.e., an element in which perform. Synonymous with control hole, the input sequence undergoes a delay function hole. of N time units. (3) See acoustic delay line, electromagnetic destructive read delay line, magnetic delay line. (ISO) A reading that also erases the data in the source location. delay line storage (ISO) A storage device that uses delay detail file lines. (ISO) Synonym for transaction file.

delay unit development time (ISO) A device that yields, after a given (1) That part of operating time used for time interval, an output signal essentially debugging new routines or hardware. similar to a previously introduced input (2) Contrast with makeup time. signal. (3) See program development time.

deleave device control character Synonym for decollate. (ISO) A control character used for the control of ancillary devices associated with delete character (DEL) a data processing system or a data com¬ (ISO) A control character used primarily munication system, e.g., for switching such to obliterate an erroneous or unwanted devices on or off. character; on perforated tape this charac¬ ter consists of a code hole in each punch diagnostic position. Pertaining to the detection and isolation of a malfunction or mistake. delimiter A flag that separates and organizes items diagnostic program of data. Synonymous with punctuation (ISO) A computer program that recog¬ symbol, separator. nizes, locates, and explains either a fault 46 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

in equipment or a mistake in a computer work used to select the leading and trail¬ program. ing edges of a pulse signal.

diagram digit See block diagram, functional diagram, (1) (ISO) A graphic character that repre¬ logic diagram, setup diagram, Veitch dia¬ sents an integer, e.g., one of the gram, Venn diagram. characters 0 to 9. (2) A symbol that represents one of the dichotomizing search nonnegative integers smaller than the (ISO) A search in which an ordered set radix. For example, in decimal nota¬ of items is partitioned into two parts, one tion, a digit is one of the characters of which is rejected, the process being from 0 to 9. repeated on the accepted part until the (3) (ISO) Synonymous with numeric search is completed. character. (4) See binary digit, borrow digit, carry digit, check digit, decimal digit, dictionary equivalent binary-digit factor, sign di¬ (1) Synonym for table. git, significant digit. (2) See relocation dictionary.

digital difference (1) (ISO) Pertaining to digits or to the (ISO) In a subtraction operation, the representation of data or physical number or quantity that is the result of quantities by digits. subtracting the subtrahend from the mi¬ (2) Contrast with analog. nuend.

digital computer differential analyzer (1) (ISO) A computer in which discrete (1) (ISO) An analog computer using inter¬ representations of data are mainly connected integrators to solve differen¬ used. tial equations. (2) A computer that operates on discrete (2) See digital differential analyzer. data by performing arithmetic and logic processes on these data. differential gear (3) Contrast with analog computer. In analog computers, a mechanism that relates the angles of rotation of three digital data shafts, usually designed so that the alge¬ (ISO) Data represented by digits, perhaps braic sum of the rotation of two shafts is with special characters and the space equal to twice the rotation of the third. character. A differential gear can be used for addi¬ tion or subtraction. digital differential analyzer (DDA) (1) (ISO) An incremental computer in differentiator which the principal type of computing A device whose output function is propor¬ unit is a digital integrator whose oper¬ tional to the derivative of the input func¬ ation is similar to the operation of an tion with respect to one or more integrating mechanism. variables, e.g., a resistance-capacitance net¬ (2) A differential analyzer that uses digital AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 47

representations for the analog quanti¬ direct access ties. (1) (ISO) The facility to obtain data from storage devices or to enter data into a digital representation storage device in such a way that the (ISO) A discrete representation of a quan¬ process depends only on the location tized value of a variable, i.e., the re¬ of that data and not on a reference to data previously accessed. presentation of a number by digits, per¬ (2) Contrast with serial access. haps with special characters and the space character. direct access storage (ISO) A storage device in which the ac¬ digitize cess time is in effect independent of the (ISO) To express or represent in a digital location of the data. Synonymous with form data that are not discrete data, e.g., immediate access storage. to obtain a digital representation of the

magnitude of a physical quantity from an direct address analog representation of that magnitude. (1) (ISO) An address that designates the storage location of an item of data to digit place be treated as an operand. (ISO) In a positional representation sys¬ Synonymous with one-level address. tem, each site that may be occupied by a (2) Contrast with indirect address. character and that may be identified by an ordinal number or by an equivalent direct addressing identifier. Synonymous with digit position, (1) (ISO) A method of addressing in symbol rank. which the address part of an instruc¬ tion contains a direct address.

digit position (2) Contrast with indirect addressing. (ISO) Synonym for digit place. direct insert subroutine (ISO) Synonym for open subroutine. digit punch (1) A punch in rows 1, 2, ..., 9 of a direct instruction punched card. (ISO) An instruction that contains the di¬ (2) Contrast with zone punch. rect address of an operand for the opera¬ (3) See also eleven punch, twelve punch. tion specified.

diminished radix complement directive (ISO) A complement obtained by sub¬ (ISO) Synonym for declaration. tracting each digit of the given number

from the number that is one less than the directory radix of that digit place. Synonymous with (ISO) A table of identifiers and references radix-minus-one complement. to the corresponding items of data.

dipole modulation disaster dump Synonym for non-polarized retum-to-zero A dump made when a nonrecoverable recording. computer program error occurs. 48 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

disc display Alternate spelling for disk. (1) (ISO) A visual presentation of data. (2) (ISO) Loosely, a display device. discrete (3) See cathode ray tube display. (1) (ISO) Pertaining to distinct elements. or to representation of data by distinct display device elements such as characters, or to (1) (ISO) An output unit that gives a physical quantities only having distinct visual representation of data. Usually values. the data are displayed temporarily, (2) Contrast with analog. however, arrangements may be made for making a permanent record. discrete data (2) See character display device. (ISO) Data represented by characters. display tube discrete programming A tube, usually a cathode ray tube, used (ISO) Synonym for integer programming. to display data.

discrete representation dividend (ISO) A representation of data by charac¬ (ISO) In a division operation, the number ters, each character or a group of charac¬ or quantity to be divided. ters designating one of a number of alter¬ natives. divisor (ISO) In a division operation, the number discrimination instruction or quantity by which the dividend is di¬ (ISO) An instruction of the class of in¬ vided. structions that comprises branch instruc¬ tions and conditional jump instructions. DLE The data link escape character. disjunction (1) (ISO) The boolean operation whose document result has the boolean value 0 if and (ISO) A data medium and the data only if each operand has the boolean recorded on it, that generally has perma¬ value 0. Synonymous with inclusive- nence and that can be read by man or OR operation, logical add, OR opera¬ machine. tion. (2) Contrast with nondisjunction. documentation (1) (ISO) The management of documents disk which may include the actions of (ISO) Synonym for magnetic disk. identifying, acquiring, processing, stor¬ ing, and disseminating them. disk pack (2) (ISO) A collection of documents on a (1) (ISO) A removable assembly of mag¬ given subject. netic disks. (2) A portable set of flat, circular record¬ document mark ing surfaces used in a disk storage de¬ (ISO) In micrographics, an optical mark, vice. within the recording area and outside the AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 49

image on a roll of microfilm, used for double precision counting images or film frames automati¬ (ISO) Pertaining to the use of two com¬ cally. Synonymous with blip. puter words to represent a number in ac¬ cordance with the required precision. document reference edge In character recognition, a specified docu¬ double pulse recording ment edge with respect to which the (ISO) Phase modulation recording magnet¬ alignment of characters is defined. ized in opposite polarity with unmagnet¬ ized regions on each end. A zero may do-nothing operation be represented by a cell composed of a (ISO) Synonym for no-operation instruc¬ negative region followed by a positive re¬ tion. gion, and a one by a positive region fol¬ lowed by a negative region, or vice versa. dot matrix (ISO) In micrographics, a method of double rail logic generating characters using a matrix of Pertaining to self-timing asynchronous cir¬ dots so that the combination of energized cuits in which each logic variable is repre¬ dots produces a human-readable character. sented by two electrical lines which together can take on three meaningful dot printer states: zero, one, and undecided. (ISO) Synonym for matrix printer. double register double card (ISO) Synonym for double-length register. A special card that is approximately twice the length of a general purpose paper doublet card. A double card usually consists of (ISO) A byte composed of two binary two separable general purpose paper elements. Synonymous with two-bit byte. cards. doubleword double-ended queue A contiguous sequence of bits or charac¬ A list of variable length, whose content ters which comprises two computer words may be changed by adding or removing and is capable of being addressed as a items at either end. unit.

double-length register downtime (ISO) Two registers that function as a The time during which a functional unit is single register. Each register may be in¬ inoperable due to a fault. dividually accessed. For example, a double-length register may be used in ex¬ drive act multiplication, for storing the result; in See tape drive. exact division, for storing the partial quo¬ tient and remainder; in character manipu¬ drop in lation, for shifting character strings and (1) (ISO) The reading of an additional accessing the left or right portion. false binary character from magnetic Synonymous with double register. storage because of a defect in, or the 50 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

presence of particles on the magnetic dummy surface layer. Pertaining to the characteristic of having (2) The reading of a spurious signal the appearance of a specified thing but whose amplitude is greater than a not having the capacity to function as predetermined percentage of the nomi¬ such. For example, a dummy character, nal signal. dummy plug, or a dummy statement.

drop out dummy instruction (1) (ISO) A failure to read a binary (ISO) An item of data in the form of an character from magnetic storage be¬ instruction that is inserted in a set of in¬ cause of defects in, or the presence of structions, but is not intended to be ex¬ particles on the magnetic surface layer. ecuted. (2) In magnetic tape, a recorded signal whose amplitude is less than a prede¬ termined percentage of a reference dump signal. (1) (ISO) Data that have been dumped. (3) In data communication, a momentary (2) (ISO) To write the contents of a stor¬ loss in signal, usually due to the effect age, or of part of a storage, usually of noise or system malfunction. from an internal storage to an exter¬ (4) A failure to read a bit from magnetic nal medium, for a specific purpose storage. such as to allow other use of the stor¬ age, as a safeguard against faults or drum errors, or in connection with debug¬ See magnetic drum. ging. (3) See change dump, disaster dump, dy¬ drum printer namic dump, postmortem dump, selec¬ A line printer in which the type are tive dump, snapshot dump, static mounted on a rotating drum that contains dump. a full character set for each printing posi¬ tion. dump routine (ISO) A utility routine that dumps. drum storage See magnetic drum storage. duodecimal (1) (ISO) Characterized by a selection, DTE choice, or condition that has twelve Data terminal equipment. possible different values or states. (2) (ISO) Of a fixed-radix numeration dual operation system, having a radix of twelve. (ISO) Of a boolean operation, another boolean operation whose result, when it is performed on operands that are the nega¬ duplex tion of the operands of the. first boolean (1) In data communication, pertaining to operation, is the negation of the result of a simultaneous two-way independent the first boolean operation. For example, transmission in both directions. disjunction is the dual operation of con¬ Synonymous with full duplex. junction. (2) Contrast with half duplex. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 51

duplicate decisions are available at each stage (ISO) To copy from a source to a desti¬ of the process. nation that has the same physical form as (2) Contrast with convex programming, the source, e.g., to punch new punched integer programming, linear program¬ cards with the same pattern of holes as ming, mathematical programming, an original punched card. Synonymous nonlinear programming, quadratic pro¬ with reproduce. gramming.

duplication check dynamic relocation A check based on the consistency of two A process that assigns new absolute ad¬ independent performances of the same dresses to a program during execution so task. that it may be executed from a different area of main storage. dyadic boolean operation (ISO) A boolean operation on two and only two operands. dynamic stop (ISO) Synonym for breakpoint halt.

dyadic operation (ISO) An operation on two and only two dynamic storage operands. A device storing data in a manner that permits the data to move or vary with dyadic operator time such that the specified data are not (ISO) An operator that represents an op¬ always available for recovery. Magnetic eration on two and only two operands. drum and disk storage are dynamic non¬ Synonymous with binary operator. volatile storage. An acoustic delay line is dynamic volatile storage. dynamic dump (ISO) Dumping performed dunng the exe¬ dynamic storage allocation cution of a computer program, usually un¬ (ISO) A storage allocation techmque in der the control of that computer program. which the storage areas assigned to com¬ puter programs and to data are deter¬ dynamicizer mined by criteria applied at the moment (ISO) Synonym for serializer. of need.

dynamic parameter (ISO) Synonym for program-generated dynamic subroutine parameter. A subroutine in skeletal form with regard to certain features, such as the number of

dynamic programming repetitions, decimal point position, or item (1) (ISO) In operations research, a proce¬ size, that are selected or adjusted in ac¬ dure for optimization of a multistage cordance with the data processing require¬ problem solution wherein a number of ments. 52 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

E editing symbols In micrographics, symbols on microfilm that are readable without magnification EAM and that provide cutting, loading, and Electrical accounting machine. other preparation instructions.

EBCDIC (Extended binary-coded decimal in¬ terchange code) editor A coded character set consisting of 8-bit See linkage editor. coded characters. editor program EBR (1) A computer program designed to per¬ Electron beam recording. form such functions as the rearrange¬ ment, modification, and deletion of echo check data in accordance with prescribed A method of checking the accuracy of rules. transmission of data in which the received (2) Contrast with linkage editor. data are returned to the sending end for comparison with the original data. EDP Electronic data processing. edge See document reference edge, reference effective address edge, stroke edge. (1) (ISO) The contents of the address

edge-coated card part of an effective instruction. A card that has been strengthened by (2) The address that is derived by apply¬ treating one or more edges. ing any specified indexing or indirect addressing rules to the specified ad¬ edge-notched card dress and that is actually used to A card in which notches representing data identify the current operand. are punched around the edges. Usually

long needles are used to select a specified effective instruction set. (ISO) An instruction that may be execut¬ ed without modification. edge-punched card A card that is punched with hole patterns eight-bit byte in tracks along the edges. Usually the Synonym for octet. hole patterns are in punch tape code. Synonymous with verge-punched card. either-or operation (ISO) Deprecated term for disjunction. edit (ISO) To prepare data for a later opera¬ tion. Editing may include the rearrange¬ electrical accounting machine (EAM) ment or the addition of data, the deletion Pertaining to data processing equipment of unwanted data, format control, code that is predominantly electromechanial conversion, and the application of stand¬ such as keypunches, mechanical sorters, ard processes such as zero suppression. collators, and tabulators. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 53

electromagnetic delay line embossment A delay line whose operation is based on (1) A distortion of the surface of a docu¬ the time of propagation of electromagnetic ment. waves through distributed or lumped (2) In character recognition, the distance capacitance and inductance. between the undistorted surface of a document and a specified part of a

electron beam recording (EBR) printed character. In micrographics, a specific method of computer output microfilming in which a emergency maintenance specifically intended to elimi¬ beam of electrons is directed onto an Maintenance nate an existing fault, that makes con¬ energy-sensitive microfilm. tinued production work unachievable.

electronic data processing (EDP) emergency maintenance time (ISO) Data processing largely performed Time, usually unscheduled, used to per¬ by electronic devices. form emergency maintenance.

electrostatic storage empty medium (ISO) A storage device that uses electri¬ (ISO) A data medium that does not con¬ cally charged areas on a dielectric surface. tain data other than a frame of reference, e.g., a preprinted form, tape punched only element with feed holes. (1) (ISO) In a set, an object, entity, or concept having the properties that de¬ empty set fine a set. Synonymous with member. (ISO) A set that has no elements. (2) See AND element, binary element, Synonymous with null set. combinational logic element, exclusive-OR element, identity element, emulate IF-AND-ONLY-IF element, IF-THEN (1) To imitate one system with another, element, inclusive-OR element, logic primarily by hardware, so that the element, majority element, NAND ele¬ imitating system accepts the same ment, NOR element, NOT element, data, executes the same computer pro¬ NOT-IF-THEN element, sequential grams, and achieves the same results logic element, threshold element. as the imitated system. (2) Contrast with simulate (2). element string

See binary element string. enabling signal A signal that permits the occurrence of an eleven-punch event. A punch in the second row from the top, on a Hollerith card. Synonymous with encode x-punch. (1) (ISO) To convert data by the use of a code or a coded character set in EM such a manner that reconversion to The end-of-medium character. the original form is possible. Encode 54 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

is sometimes loosely used when com¬ end-of-tape marker (EOT) plete reconversion is not possible. A marker on a magnetic tape used to in¬ (2) Synonymous with code. dicate the end of the permissible record¬ (3) Contrast with decode. ing area, e.g., a photo reflective strip, a transparent section of tape, a particular bit pattern. encoder (1) (ISO) A device that encodes data. end-of-text character (ETX) (2) (ISO) A device that has a number of (ISO) A transmission control character input lines of which not more than used to terminate a text. one may carry a signal and a number of output lines of which any number end-of-transmission-block character (ETB) may carry signals, there being a one- (ISO) A transmission control character to-one correspondence between the used to indicate the end of a transmission combinations of output signals and the block of data when data are divided into input signals. such blocks for transmission purposes. (3) Contrast with decoder.

end-of-transmission character (EOT) end-around borrow (ISO) A transmission control character (ISO) The action of transferring a borrow used to indicate the conclusion of a trans¬ digit from the most significant digit place mission which may have included one or to the least significant digit place. more texts and any associated message headings.

end-around carry (ISO) The action of transferring a carry ENQ digit from the most significant digit place The enquiry character to the least significant digit place. An end-around carry may be necessary when enquiry character (ENQ) adding two negative numbers that are (ISO) A transmission control character represented by their diminished radix used as a request for a response from the complements. station with which the connection has been set up, which response may include station identification, the type of equip¬ end-around shift ment in service, and the status of the A shift in which the data moved out of remote station. one end of the storing register are reen¬ tered into the other end. Synonymous entrance with circular shift. (ISO) Synonym for entry point.

end-of-medium character (EM) entropy (ISO) A control character that may be (1) (ISO) In information theory, the mean used to identify the physical end of the value of the measure of information data medium, the end of the used portion conveyed by the occurrence of any of the medium, or the end of the wanted one of a finite number of mutually portion of the data recorded on the medi¬ exclusive and jointly exhaustive events um. of definite probabilities: in mathemati- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 55

cal notation, this mean H(x) for a set function or purpose. Synonymous of events x,...xn with the probabilities with entrance, entry. p( Xj )...p( xn) equals the mathematical (2) In a routine, any place to which con¬ expectation, or mean value, of the in¬ trol can be passed. formation content fix^ of the in¬ dividual events, i.e.. EOT (1) The end-of-transmission character. (2) End-of-tape marker.

n equipment 1 H(x) p(xj)I(xj) = £ p(xj) log See data terminal equipment, peripheral E p(Xj) i=1 i=1 equipment.

equivalence A logic operator having the property that if P is a statement, Q is a statement, R is a statement,... then the equivalence of P, Synonymous with average information Q, R,... is true if and only if all state¬ content, mean information content, ments are true or all statements are false. (2) See character mean entropy, condition¬ al entropy. equivalence operation (1) (ISO) The dyadic boolean operation entry whose result has the boolean value 1 (ISO) Synonym for entry point. if and only if the operands have the same boolean value. Synonymous entry conditions with IF-AND-ONLY-IF operation. (1) (ISO) The conditions to be specified (2) Contrast with nonequivalence opera¬ on entering a computer program, a tion. routine, or a subroutine. For exam¬ ple, the address of those locations equivalent-binary-digit factor from which the program, routine, or The average number of binary digits re¬ subroutine will take its operands and quired to express one radix digit in a of those locations with which its entry non-binary numeration system. For exam¬ points and exits will be linked. ple, approximately 3!h, times the number (2) The initial data and control conditions of decimal digits is required to express a to be satisfied for successful execution decimal numeral as a binary numeral. of a given routine.

equivocation entry point (ISO) In information theory, the condi¬ (1) (ISO) The address or the label of the tional entropy of the occurrence of specific first instruction executed upon entering messages at the message source given the a computer program, a routine, or a occurrence of specific messages at a mes¬ subroutine. A computer program, a sage sink connected to the message source routine, or a subroutine may have a by a specified channel. If x; is the input number of different entry points, each message at the message source and y- the perhaps corresponding to a different output message at the message sink, the 56 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

equivocation is noted as the conditional error control character entropy H(x jy). The equivocation is the Synonym for accuracy control character. mean additional information content that must be supplied per message at the mes¬ error correcting code sage sink to correct the received messages A code in which each acceptable expres¬ affected by a noisy channel. sion conforms to specific rules of construc¬ tion that also define one or more equiva¬ lent nonacceptable expressions, so that if erasable storage certain errors occur in an acceptable ex¬ (1) (ISO) A storage device whose contents pression the result will be one of its can be modified. equivalents and thus the error can be cor¬ (2) Contrast with fixed storage, permanent rected. storage.

error detecting code erase A code in which each expression conforms (ISO) To remove all previous data from to specific rules of construction, so that if magnetic storage by changing it to a certain errors occur in an expression the specified condition; that may be an un¬ resulting expression will not conform to magnetized state or a predetermined mag¬ the rules of construction and thus the pre¬ netized state. sence of the errors is detected. Synony¬ mous with self-checking code.

erase character (ISO) Deprecated term for delete charac¬ error message ter. An indication that an error has been detected.

error error range (1) (ISO) A discrepancy between a com¬ (1) (ISO) The set of values that an error puted, observed, or measured value or may take. condition and the true, specified, or (2) (ISO) Deprecated term for error span. theoretically correct value or condition. (2) (ISO) Deprecated term for mistake. error ratio (3) Contrast with failure, fault, malfunc¬ The ratio of the number of data units in tion, mistake. error to the total number of data units. (4) See absolute error, balanced error, bias error, inherited error, relative er¬ error span ror, rounding error, truncation error. (ISO) The difference between the highest and the lowest error values. error burst

In data communication, a sequence of sig¬ ESC nals containing one or more errors but The escape character. counted only as one unit in accordance

with some specific criterion or measure. escape character (ESC) An example of a criterion is that if three (1) (ISO) A code extension character consecutive correct bits follow an errone¬ used, in some cases with one or more ous bit, then an error burst is terminated. succeeding characters, to indicate by AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 57

some convention or agreement that (2) A logic operator having the property the coded representations following the that if P is a statement and Q is a character or the group of characters statement, then P exclusion Q is true are to be interpreted according to a if P is true and Q is false, false if P different code or according to a differ¬ is false, and false if both statements ent coded character set. are true. P exclusion Q is often (2) See data link escape character. represented by a combination of “AND” and “NOT” symbols such as ETB P~AQ. The end-of-transmission-block character. (3) (ISO) Synonymous with NOT-IF THEN operation. ETX

The end-of-text character. exclusive-OR (1) A logic operator having the property event posting that if P is a statement and Q is a The saving of the computer program and statement, then P exclusive-OR Q is the data context of a task and establish¬ true if either but not both statements ing the program and data of another task are true, false if both are true or both to which control is to be passed, based are false. P exclusive-OR Q is often on an event such as completion of loading represented by P©Q, P ¥ Q. of data into main storage. (2) Contrast with OR.

except operation exclusive-OR element (ISO) Deprecated term for exclusion. (ISO) A logic element that performs the boolean nonequivalence operation. excess-three code Synonymous with exclusive-OR gate. (ISO) The binary-coded decimal notation in which a decimal digit n is represented exclusive-OR gate by the binary numeral that represents (ISO) Synonym for exclusive-OR element. (n+3).

exclusive-OR operation exchange sort (ISO) Synonym for nonequivalence opera¬ A sort in which succeeding pairs of items tion. in a set are examined; if the items in a pair are out of sequence according to the execute specified criteria, the positions of the items are exchanged; e.g., a bubble sort. This (1) (ISO) In programming, to change the process is repeated until all items are sort¬ state of a computer in accordance ed. with the rules of the operations it recognizes.

exclusion (2) (ISO) To perform the execution of an (1) (ISO) The dyadic boolean operation instruction or of a computer program. whose result has the boolean value 1 if and only if the first operand has execute phase the boolean value 1 and the second (ISO) Of a run, the logical subdivision has the boolean value 0. that includes the execution of the target 58 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

program. Synonymous with executing expression phase. A configuration of signs.

executing phase extended time scale (ISO) Synonym for execute phase. (1) The time scale used in data processing when the time scale factor is greater

execution than one. Synonymous with slow (1) (ISO) In programming, the process by time scale. (2) Contrast with fast time scale. which a computer program or subrou¬ tine changes the state of a computer extension character in accordance with the rules of the See code extension character. operations that a computer recognizes. (2) (ISO) The process of carrying out an external delays instruction by a computer. Time lost due to circumstances beyond the (3) (ISO) The process of carrying out the control of the operator or maintenance en¬ instructions of a computer program by gineer, e.g., failure of external power a computer. source.

executive program external program parameter (ISO) Synonym for supervisory program. (ISO) In a computer program, a parame¬ ter that must be bound during the calling executive routine of the computer program. (ISO) Synonym for supervisory routine. external sort exit (1) A sort that requires the use of auxili¬ (ISO) Any instruction in a computer ary storage because the set of items to program, in a routine, or in a subroutine be sorted cannot be held in the avail¬ after the execution of which control is no able internal storage at one time. longer exercised by that computer pro¬ (2) A sort program, or a sort phase of a multipass sort, that merges strings of gram, that routine, or that subroutine. items, using auxiliary storage, until one string is formed. explicit address (ISO) Synonym for absolute address. external storage (ISO) In a hierarchy of storage devices of exponent a data processing system, any storage de¬ (ISO) In a floating-point representation, vice that is not internal storage. External the numeral that denotes the power to storage and internal storage are terms which the implicit floating point base is which take on precise meanings only with raised before being multiplied by the reference to a particular configuration. fixed-point part to determine the real

number represented, e.g., a floating point extract representation of the number 0.0001234 is (ISO) To select and remove from a set of 0.1234-3, where 0.1234 is the fixed-point items those items that meet some criteria, part and -3 is the exponent. e.g., to obtain certain specified digits from AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 59

a computer word as controlled by an in¬ struction or a mask.

extract instruction An instruction that requests the formation of a new expression from selected parts of given expressions. 60 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

F FC The font change character.

face change character FE (ISO) Synonym for font change character. The format effector character.

factor feedback loop (1) (ISO) In a multiplication operation, The components and processes involved in any of the numbers or quantities that correcting or controlling a system by using are the operands. part of the output as input. (2) See equivalent-binary-digit factor, mul¬ tiplier factor, relocation factor, scale feedback system factor, time scale factor. See information feedback system.

factorial feed hole (ISO) The product of the positive integers (ISO) A hole punched in a data medium 1, 2, 3, up to and including a given inte¬ to enable it to be moved or synchronized. ger. Synonymous with sprocket hole.

failure feed pitch (1) (ISO) The termination of the capabili¬ (ISO) The distance between corresponding ty of a functional unit to perform its points of adjacent feed holes along the required function. A failure is the ef¬ feed track. fect of a fault. Synonymous with

malfunction. feed punch (2) Contrast with error, fault, mistake. See automatic-feed punch.

false add feed track To form a partial sum, i.e., to add with¬ The track of a tape that contains the feed out carries. holes.

fast time scale ferrite (1) The time scale used in data processing An iron compound frequently used in the when the time scale factor is less than construction of magnetic cores. one.

(2) Contrast with extended time scale. fetch To locate and load a quantity of data fault from storage. (1) (ISO) An accidental condition that causes a functional unit to fail to per¬ FF form in a required manner. The form feed character. (2) Contrast with error, failure, mistake. (3) See pattern sensitive fault, program Fibonacci number sensitive fault. An integer in the Fibonacci series. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 61

Fibonacci search file (ISO) A dichotomizing search in which (1) (ISO) A set of related records treated the number of items in the set is equal to as a unit, e.g., in stock control, a file a Fibonacci number or is assumed to be could consist of a set of invoices. equal to the next higher Fibonacci num¬ (2) See inverted File, master file, transac¬ ber and then at each step in the search tion File. the set of items is partitioned in accord¬ ance with the Fibonacci series. The file gap Fibonacci series is the series 0, 1, 1, 2, 3, An area on a data medium intended to 5, 8, each term being the sum of the be used to indicate the end of a file, and two preceding terms. It is usually ex¬ possibly, the start of another. A file gap pressed in mathematics as: X, = Xi t + is frequently used for other purposes, in Xi2 where X0 = 0 and X, = 1. particular, as a flag to indicate the end or beginning of some other group of data.

Fibonacci series A series of integers in which each integer file layout is equal to the sum of the two preceding (ISO) The arrangement and structure of integers in the series. The series is for¬ data or words in a File including the or¬ mulated mathematically by Xt = Xj( + der and size of the components of the Xi2, where X0 = 0 and X, = 1, i.e., 0, 1, file. 1, 2, 3, 5, 8, 13, 21.... file maintenance (ISO) The activity of keeping a file up to fiche date by adding, changing, or deleting See microfiche. data.

field file separator character (FS) (1) (ISO) In a record, a specified area (ISO) The information separator intended used for a particular category of data, to identify a logical boundary between e.g, a group of card columns in items called files. which a wage rate is recorded. (2) A group of adjacent card columns on filler a punch card. (ISO) One or more characters adjacent to (3) See card Field, common field. an item of data that serve to bring its re¬ presentation up to a specified size. FIFO (first-in-first-out)

A queuing technique in which the next film frame item to be retrieved is the item that has (1) (ISO) In micrographics, that area of been in the queue for the longest time. microfilm exposed during each expo¬ sure, whether or not this area is filled figurative constant by an image. (1) (ISO) A data name that is reserved (2) Synonymous with recording area. for a specified constant in a specified programming language. film storage (2) (ISO) Deprecated term for literal. See magnetic thin Film storage. 62 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

filter a particular user, or nonerasable when A device or program that separates data, operating under particular conditions, signals, or material in accordance with e.g., a storage when controlled by a specified criteria. lockout feature, a photographic disk. Synonymous with nonerasable storage, five-bit byte permanent storage, read-only memory, (ISO) Synonym for quintet. read-only storage. (2) Contrast with erasable storage.

fixed-cycle operation An operation that is completed in a speci¬ nag fied number of regularly timed execution (1) Any of various types of indicators cycles. used for identification, e.g., a word mark. fixed-point part (2) A character that signals the occurrence (ISO) In a floating-point representation, of some condition, such as the end of the numeral that is multiplied by the ex¬ a word. ponentiated implicit floating-point base to (3) (ISO) Deprecated term for mark. determine the real number represented, (4) (ISO) Synonym for switch indicator. e.g., a floating-point representation of the (5) Synonymous with sentinel. number 0.0001234 is 0.1234-3, where .1234 is the fixed-point part and -3 is the flash exponent. Synonymous with mantissa. See form flash.

fixed-point representation system flash card (ISO) A radix numeration system in (ISO) In micrographics, a target printed which the radix point is implicitly fixed in with distinctive markings that is photo¬ the series of digit places by some conven¬ graphed to facilitate the indexing of mi¬ tion upon which agreement has been crofilm. reached. flip-flop fixed-radix numeration system A circuit or device containing active ele¬ (ISO) A radix numeration system in ments, capable of assuming either one of which all the digit places, except perhaps two stable states at a given time. Sy¬ the one with the highest weight, have the nonymous with bistable circuit, toggle (1). same radix. The weights of successive di¬ git places are successive integral powers of floating-point base a single radix, each multiplied by the (ISO) In a floating-point representation same factor. Negative integral powers of system, the implicit fixed positive integer the radix are used in the representation of base, greater than unity, that is raised to fractions. A fixed-radix numeration sys¬ the power explicitly denoted by the expo¬ tem is a particular case of a mixed-radix nent in the floating-point representation or numeration system. represented by the characteristic in the floating-point representation and then mul¬ fixed storage tiplied by the fixed-point part to deter¬ (1) A storage device whose contents are mine the real number represented, e.g., in inherently nonerasable, nonerasable by the floating-point representation of the AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 63

number 0.0001234, namely 0.1234-3, the flowchart symbol implicit floating-point base is 10. Synony¬ (ISO) A symbol used to represent opera¬ mous with floating-point radix. tions, data, flow, or equipment on a flow¬ chart. floating-point radix Synonym for floating-point base. flowchart text The descriptive information that is as¬ floating-point register sociated with flowchart symbols. (ISO) A register used to manipulate data in floating-point representation. flow diagram (ISO) Deprecated term for flowchart.

floating-point representation (1) (ISO) A representation of a real num¬ flow direction ber in a floating-point representation (ISO) On a flowchart, the antecedent system, e.g., a floating-point represen¬ to-successor relation between the symbols. tation of the number 0.0001234 is 0.1234-3, where 0.1234 is the fixed- flowline point part and -3 is the exponent. The (ISO) On a flowchart, a line representing numerals are expressed in the a connecting path between flowchart sym¬ variable-point decimal numeration sys¬ bols, e.g., a line to indicate a transfer of tem. data or control. (2) Contrast with variable-point represen¬ tation. fluerics The area within the field of fluidics in flow which components and systems perform See bidirectional flow, normal direction functions such as sensing, logic, amplifica¬ flow, reverse direction flow. tion, and control without the use of me¬ chanical parts.

flow analysis (1) In compilers, a technique used to de¬ fluidic termine the specific interdependencies Pertaining to the sensing, control, informa¬ of elements of a computer program. tion processing, and actuation functions (2) The detection and recording of the performed through the use of fluid dy¬ sequencing of instructions in computer namic phenomena. programs, for example as used in monitors and debugging routines. fluidics That branch of science and technology

flowchart concerned with sensing, control, informa¬ (1) (ISO) A graphical representation of tion processing, and actuation functions the definition, analyis, or method of performed through the use of fluid dy¬ solution of a problem, in which sym¬ namic phenomena. bols are used to represent operations, data, flow, equipment, etc. flying spot scanner (2) Contrast with block diagram. In optical character recognition, a device (3) See data flowchart, programming employing a moving spot of light to scan flowchart. a sample space, the intensity of the trans- 64 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

mitted or reflected light being sensed by a format effector (FE) photoelectric transducer. (ISO) Any control character used to con¬ trol the positioning of printed, displayed, fold or recorded data. Synonymous with lay¬ To compact data by combining parts of out character. the data, e.g., to transform a two- word al¬ phabetic key into a one-word numeric key form feed character (FF) by adding the numeric equivalents of the (ISO) A format effector that causes the letters. print or display position to move to the next predetermined first line on the next font form, the next page, or the equivalent. (1) A family or assortment of characters of a given size and style, e.g., 9 point form flash Bodom Modem.. (ISO) To project a constant pattern such (2) See type font. as a report form, grid, or map as back¬ ground for a display. Synonymous with font change character (FC) form overlay. (ISO) A control character that selects and makes effective a change in the specific form overlay shape, or size, or shape and size of the (ISO) Synonym for form flash. graphics for a set of graphemes, the character set remaining unchanged. Sy¬ formula manipulation nonymous with face change character. Algebraic manipulation of mathematical formulae. forbidden combination (1) A combination of bits or other re¬ FORTRAN (formula translation) presentations that is not valid accord¬ A programming language primarily used ing to some criteria. to express computer programs by arith¬ (2) Contrast with illegal character. metic formulas.

foreground processing four-address (1) (ISO) The execution of a computer Pertaining to an instruction format con¬ program that preempts the use of taining four address parts. computer facilities. (2) Contrast with background processing. four-bit byte (ISO) Synonym for quartet. formal logic (ISO) The study of the structure and form of four-plus-one address valid argument without regard to the meaning of Pertaining to an instruction that contains the terms in the argument. four operand addresses and the address of the next instruction to be executed. format (1) (ISO) The arrangement or layout of frame data in or on a data medium. (1) (ISO) That portion of a tape, on a (2) See address format, instruction format. line perpendicular to the reference AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 65

edge, on which binary characters may full subtracter be written or read simultaneously. (ISO) A combinational circuit that has (2) See film frame. three inputs that are a minuend, I, a sub¬ trahend, J, and a borrow digit, K, trans¬ ferred from another digit place, and two FS outputs that are a difference, W, and a The fde separator character. new borrow digit, X; and in which the outputs are related to the inputs according full adder to the following table: (ISO) A combinational circuit that has three inputs that are an augend, D, an addend, E, and a carry digit transferred from another digit place, F; and two out¬ Input 1 minuend 0 0 1 1 0 0 1 1 Input J subtrahend 0 1 0 1 0 1 0 1 puts that are a sum without carry, T, and Input K borrow digit 0 0 0 0 1 1 1 1 Output W difference 0 1 1 0 1 0 0 1 a new carry digit, R, and in which the Output X borrow digit 0 1 0 0 1 1 0 1 outputs are related to the inputs according to the following table:

Full subtracter block diagram Input D augend 0 0 1 1 0 0 1 1 Input E addend 0 1 0 1 0 1 0 1 Input F carry digit 0 0 0 0 1 1 1 1 Output T sum without carry 0 1 1 0 1 0 0 1 Output R carry digit 0 0 0 1 0 1 1 1 Full subtracter block diagram

Synonymous with three-input adder.

Full adder block diagram fullword (ISO) Synonym for computer word.

function (l)(ISO) A mathematical entity whose value, i.e., the value of the dependent variable, depends in a specified man¬ ner on the values of one or more in¬ dependent variables, not more than one value of the dependent variable full duplex corresponding to each permissible Synonym for duplex combination of values from the re- 66 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

spective ranges of the independent both capable of accomplishing a specified variables. purpose. (2) A specific purpose of an entity, or its characteristic action. function hole (3) In data communication, a machine ac¬ tion such as carriage return or line (ISO) Synonym for designation hole. feed. (4) In computer programming, synonym function part for procedure. (ISO) Synonym for operation part. (5) See boolean function, generating func¬ tion, mathematical function, recursive function, threshold function. function table (1) Two or more sets of data so arranged functional design that an entry in one set selects one or

(ISO) The specification of the working re¬ more entries in the remaining sets, lationships among the parts of a data e.g., a tabulation of the values of a processing system. function for a set of values of the variable, a dictionary. functional diagram (2) A device constructed of hardware, or A diagram that represents the working re¬ lationships among the parts of a system. a subroutine, which can either decode multiple inputs into a single output or

functional unit encode a single input into multiple (ISO) An entity of hardware, software, or outputs. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 67

G generated address (ISO) An address that has been formed as a result during the execution of a com¬ gang punch puter program. Synonymous with synthet¬ To punch identical data into a card deck. ic address.

gap character generating function (ISO) A character that is included in a (ISO) Of a given series of functions or computer word for technical reasons but constants, a mathematical function that, does not represent data. when represented by an infinite series, has those functions or constants as coefficients gate in the series. (1) (ISO) A combinational circuit with only one output channel. generation (2) (ISO) A device having one output (ISO) In micrographics, a measure of the channel and one or more input chan¬ remoteness of the copy from the original nels, such that the output channel material, the first microfilm representation state is completely determined by the being the first generation microfilm. input channel states, except during switching transients. generator (3) A combinational logic element having (1) A controlling routine that performs a at least one input channel. generating function, e.g., report gener¬ (4) See AND gate, OR gate. ator, I/O generator. (2) See compiler generator, macrogenera¬ tor. general purpose computer (ISO) A computer that is designed to op¬ global erate upon a wide variety of problems. (1) Pertaining to that which is defined in one subdivision of a computer pro¬ general-purpose paper card gram and used in at least one other A card that meets the specifications in ap¬ subdivision of that computer program. plicable ISO standards, except for the (2) Contrast with local. printed card form.

graphic general-purpose register (ISO) A symbol produced by a process (ISO) A register, usually explicitly ad¬ such as handwriting, drawing, or printing. within a of registers, that dressable set Synonymous with graphic symbol. can be used for different purposes, such

as an accumulator, as an index register, as graphic character a special handler of data or code formats. (ISO) A character, other than a control character, that is normally represented by generate a graphic. To produce a computer program by a se¬ lection of subsets from skeletal code under graphic symbol the control of parameters. (ISO) Synonym for graphic. 68 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

gray code group separator character (GS)

A binary code in which sequential num¬ (ISO) The information separator intended bers are represented by binary expressions, to identify a logical boundary between each of which differs from the preceding items called groups. expression in one place only. Synony¬ mous with reflected binary code.

grid In optical character recognition, two mutu¬ GS ally orthogonal sets of parallel lines used for specifying or measuring character im¬ The group separator character. ages.

group mark (ISO) A mark that identifies the begin¬ ning or the end of a set of data which guide edge may include blocks, words, or other items. (ISO) Synonym for reference edge. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 69

H A contiguous sequence of bits or charac¬ ters which comprises half a computer word and is capable of being addressed half adder as a unit. (ISO) A combinational circuit that has two inputs A and B and two outputs, one halt being a sum without carry, S, and the See breakpoint halt. other being a carry, C, and in which the outputs are related to the inputs according halt instruction to the following table: (ISO) Synonym for pause instruction.

hamming code Input A 0 0 1 1 A data code which is capable of being Input B 0 1 0 1 corrected automatically.

Output S sum without carry 0 1 1 0 hamming distance Output C carry 0 0 0 1 Synonym for signal distance.

hand-feed punch (ISO) A keypunch into which punch cards Synonymous with two-input adder. or punched cards are manually entered and removed one at a time. half-duplex

(1) In data communication, pertaining to hardware an alternating, one way at a time, in¬ (1) (ISO) Physical equipment used in data dependent transmission. processing, as opposed to computer (2) Contrast with duplex. programs, procedures, rules, and as¬ sociated documentation. half subtracter (2) Contrast with software. (ISO) A combinational circuit that has two inputs that are a minuend, G, and a hardware check subtrahend, H; and two outputs that are a Synonym for automatic check. difference, U, and a borrow digit, V, and in which the outputs are related to the in¬ Hartley puts according to the following table: (ISO) In information theory, a unit of logarithmic measures of information equal to the decision content of a set of ten mutually exclusive events expressed by the Input G minuend 0 0 1 1 logarithm with the base ten, e.g., the deci¬ Input H subtrahend 0 1 0 1 sion content of a character set of eight Output U difference 0 1 1 0 characters equals 0.903 Hartley. Output D borrow digit 0 1 0 0 Synonymous with information content decimal unit.

hash total halfword The result obtained by applying an al- 70 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

gorithm to a set of data for checking pur¬ high-speed carry poses, e.g., a summation obtained by (1) (ISO) In parallel addition, any proce¬ treating data items as numbers. dure for speeding up the processing of carries, e.g., standing-on-nines carry. head (2) Contrast with cascaded carry. (1) A device that reads, writes, or erases data on a storage medium, e.g., a hit small electromagnet used to read, (1) A comparison of two items of data write, or erase data on a magnetic that satisfies specified conditions. drum or magnetic tape, or the set of Contrast with match. perforating, reading, or marking de¬ (2) A transient disturbance to a communi¬ vices used for punching, reading, or cation medium. printing on perforated tape. (2) See pre-read head, read head, read/ hit-on-the-fly printer write head, write head. (ISO) Synonym for on-the-fly printer.

header card hole pattern A card that contains information related (1) (ISO) An array of holes that repre¬ to the data in cards that follow. sents data, e.g., a punching configura¬ tion that represents a single character. heading (2) A punching configuration within a (1) In ASCII and data communication, a card column that represents a single sequence of characters preceded by character of a character set. the start-of-heading character used as machine sensible address or routing Hollerith information. Pertaining to a particular type of code or (2) Contrast with text. punched card utilizing 12 rows per co¬ lumn and usually 80 columns per card. heading character See start-of-headmg character. Hollerith card A punch card characterized by 80 co¬ heuristic method lumns and 12 rows of punch positions. (ISO) Any exploratory method of solving problems in which an evaluation is made horizontal feed of the progress toward an acceptable final Pertaining to the entry of a punch card result using a series of approximate re¬ into a card feed with a long edge first. sults. horizontal positions hexadecimal See addressable horizontal positions. (ISO) Synonym for sexadecimal. horizontal tabulation character (HT) high-level language (ISO) A format effector character that (ISO) A programming language that does causes the print or display position to not reflect the structure of any one given move forward to the next of a series of computer or that of any given class of predetermined positions along the same computers. line. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 71

housekeeping operation HT (ISO) An operation that facilitates the The horizontal tabulation character. execution of a computer program without making a direct contribution. For exam¬ hybrid computer ple, initialization of storage areas; the exe¬ (ISO) A computer using both analog and cution of a calling sequence. Synonymous discrete representation of data. with overhead operation. hysteresis loop See magnetic hysteresis loop. 72 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

I IF-AND-ONLY-IF gate (ISO) Synonym for IF-AND-ONLY-IF element. identifier (ISO) A character or group of characters IF-AND-ONLY-IF operation used to identify or name an item of data (ISO) Synonym for equivalence operation. and possibly to indicate certain properties of that data. IF-THEN element (ISO) A logic element that performs the identity element boolean operation of implication. (ISO) A logic element that performs an Synonymous with IF-THEN gate. identity operation. Synonymous with identity gate. IF-THEN gate (ISO) Synonym for IF-THEN element. identity gate

(ISO) Synonym for identity element. IF-THEN operation (ISO) Synonym for implication. identity operation

(1) (ISO) The boolean operation the re¬ ignore character sult of which has the boolean value 1 (ISO) Synonym for cancel character. if and only if all the operands have the same boolean value. An identity illegal character operation on two operands is an (1) A character or combination of bits equivalence operation. that is not valid according to some (2) Contrast with nonidentity operation. criteria, e.g., with respect to a speci¬ fied alphabet a character that is not a identity unit member. An n-input unit that yields a specified (2) Contrast with forbidden combination. output signal only when all n-input signals are alike. image See card image, cine-oriented image, idle character comic-strip-oriented image. See synchronous idle character.

image area idle time In micrographics, that part of the film (1) (ISO) Operable time during which a frame reserved for an image. functional unit is not operated.

(2) Contrast with operating time. image dissector In optical character recognition, a me¬ IDP chanical or electronic transducer that se¬ Integrated data processing. quentially detects the level of light intensi¬ ty in different areas of a completely il¬ IF-AND-ONLY-IF element luminated sample space. (ISO) A logic element that performs the boolean operation of equivalence. immediate access storage Synonymous with IF-AND-ONLY-IF gate. A storage device whose access time is AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 73

negligible in comparison with other devices such as those used with credit operating times. cards and address plates.

immediate address imprinting (ISO) The contents of an address part (1) The act of using an imprinter. that contains the value of an operand (2) The output of any imprinter. rather than an address. Synonymous with

zero-level address. impulse Synonym for pulse. immediate addressing

(ISO) A method of addressing in which incidental time the address part of an instruction contains (ISO) Synonym for miscellaneous time. an immediate address.

inclusion immediate instruction (ISO) Deprecated term for implication. (ISO) An instruction that contains within itself an operand for the operation speci¬ inclusive-OR element fied, rather than an address of the ope¬ (ISO) A logic element that performs the rand. boolean operation of disjunction. Synonymous with inclusive-OR gate. impact printer (ISO) A printer in which printing is the inclusive-OR gate result of mechanical impacts. (ISO) Synonym for inclusive-OR element.

imperative statement inclusive-OR operation (ISO) Synonym for instruction. (ISO) Synonym for disjunction.

implication inconnector (ISO) The dyadic boolean operation the (1) In flowcharting, a connector that indi¬ result of which has the boolean value 0 if cates a continuation of a broken tlow- and only if the first operand has the boo¬ line. lean value 0 and the second has the boo¬ (2) Contrast with outconnector. lean value 1. Synonymous with condition¬ al implication operation, IF-THEN opera¬ tion. incremental computer (1) (ISO) A computer in which incremen¬

implied addressing tal representation of data is mainly (ISO) A method of addressing in which used. the operation part of an instruction implic¬ (2) A special purpose computer that is itly addresses operands. specifically designed to process changes in the variables as well as

imprinter the absolute value of the variables. Any device used to produce or impress marks or patterns on a surface, e.g., print¬ incremental integrator ing presses, typewriters, pens, cash regis¬ A digital integrator modified so that the ters, bookkeeping machines, and pressure output signal is maximum negative, zero, 74 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

or maximum positive when the value of execution of a loop, to control the use of the input is negative, zero, or positive. an array, as a switch, for table lookup, as a pointer, etc. Synonymous with modifier incremental representation register. (1) (ISO) A method of representing varia¬ bles in which changes in the values of index word the variables are represented, rather (ISO) An index modifier applied to the than the values themselves. address part of a computer instruction. (2) See ternary incremental representation. indicator index (1) (ISO) A device that may be set into (1) (ISO) In programming, a subscript, of a prescribed state, usually according to integer value, that identifies the posi¬ the result of a previous process or on tion of an item of data with respect the occurrence of a specified condition to some other item of data. in the equipment, and that usually (2) (ISO) A list of the contents of a file gives a visual or other indication of or of a document, together with keys the existence of the prescribed state, or references for locating the contents. and that may in some cases be used (3) A symbol or a numeral used to iden¬ to determine the selection among al¬ tify a particular quantity in an array ternative next processes, e.g., an over¬ of similar quantities. For example, flow indicator. the terms of an array represented by (2) An item of data that may be interro¬ XI, X2, ..., XI00 have the indexes 1, gated to determine whether a particu¬ 2,..., 100 respectively. lar condition has been satisfied in the (4) In micrographics, a guide for locating execution of a computer program, e.g., information on a roll of microfilm us¬ a switch indicator, an overflow indica¬ ing targets, flash cards, lines, bars, or tor. other optical codes. (3) See switch indicator. (5) To prepare a list as in (2). (6) To move a machine part to a prede¬ indirect address termined position, or by a predeter¬ (1) (ISO) An address that designates the mined amount, on a quantized scale. storage location of an item of data to (7) See code line index. be treated as the address of an ope¬ rand, but not necessarily as its direct indexed address address. Synonymous with multilevel An address which is modified by the con¬ address. tent of an index register prior to or dur¬ (2) Contrast with direct address. ing the execution of a computer instruc¬ tion. indirect addressing (1) A method of addressing in which the index register address part of an instruction contains (ISO) A register whose contents may be an indirect address. used to modify an operand address during (2) Contrast with direct addressing. the execution of computer instructions, so as to operate as a clock or counter. An indirect instruction index register may be used to control the (ISO) An instruction that contains the in- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 75

direct address of an operand for the oper¬ expressed as the logarithm of the ation specified. reciprocal of the probability p(xf) that the particular event will occur: i.e., induction See mathematical induction.

I(xi) = l°9 7(7) =-|o9P infinite pad method In optical character recognition, a method of measuring reflectance of a paper stock such that doubling the number of backing (2) See conditional information content, sheets of the same stock will not change joint information content. the measured reflectance.

information content binary unit infix notation (ISO) Synonym for Shannon. (1) (ISO) A method of forming math¬

ematical expressions, governed by information content decimal unit rules of operator precedence and using (ISO) Synonym for Hartley. parentheses, in which the operators

are dispersed among the operands, information content natural unit (NAT) each operator indicating the operation (ISO) In information theory, a unit of to be performed on the operands or logarithmic measures of information ex¬ the intermediate results adjacent to it. pressed by the naperian logarithm, e.g., If it is desired to distinguish the case the decision content of a character set of in which there are more than two eight characters equals 2.079 natural units operands for an operation, the term of information. distributed infix notation may be used.

(2) Contrast with parentheses-free nota¬ information feedback system tion, prefix notation, postfix notation. A data transmission system that uses an echo check to verify the accuracy of the information transmission. (ISO) The meaning that a human assigns to data by means of the known conven¬ information interchange tions used in their representation. The process of sending and receiving data in such a manner that the information information bits content or meaning assigned to the data In telecommunications, those bits which is not altered during the transmission. are generated by the data source and which are not used for error control by information measure the data transmission system. (ISO) In information theory, a suitable function of the frequency of occurrence of information content a specified event from a set of possible (l)(ISO) In information theory, a meas¬ events conventionally taken as a measure ure of information conveyed by the of the relative value of the intelligence occurrence of an event of definite conveyed by this occurrence. In informa¬ probability; in mathematical notation, tion theory, the term event is to be un¬ the measure I(x;) for the event x; is derstood as used in the theory of proba- 76 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

bility. For instance, the presence of a initialize given element of a set, the occurrence of (1) To set counters, switches, addresses, or a specified character or of a specified contents of storage to zero or other word in a message. starting values at the beginning of, or at prescribed points in, the operation of a computer routine. information processing (2) Contrast with prestore. (ISO) Synonym for data processing.

initial program loader (IPL) information rate (1) (ISO) The utility routine that loads See average information rate. the initial part of a computer pro¬ gram, such as an operating system or information retrieval other computer program, so that the (1) (ISO) The action of recovering specific computer program can then proceed information from stored data. under its own control. (2) (ISO) Methods and procedures for (2) Contrast with bootstrap, bootstrap recovering specific information from loader. stored data.

inline procedures information separator (IS) In COBOL, the set of statements that con¬ (ISO) Any control character used to deli¬ stitutes the main or controlling flow of the mit like units of data in a hierarchic ar¬ computer program and which excludes rangement of data. The name of the statements executed under control of the separator does not necessarily indicate the asynchronous control system. units of data that it separates. Synonymous with separating character. inoperable time (ISO) The time during which a functional information source unit would not yield correct results if it (ISO) Synonym for message source. were operated. It is assumed that all en¬ vironmental conditions for proper opera¬

information theory tion are met. (ISO) The branch of learning concerned with the study of measures of information input (1) One, or a sequence of, input states. and their properties. (2) (ISO) Pertaining to a device, process, or channel involved in an input proc¬ inherited error ess, or to the data or states involved An error carried forward from a previous in an input process. In the English step in a sequential process. language, the adjective input may be used in place of input data, input sig¬ inhibiting signal nal, input terminal, etc., when such A signal that prevents the occurrence of usage is clear in a given context. an event. (3) (ISO) Synonym for input data, input process. initialization (4) Synonym for input channel. See loop initialization. (5) See manual input, real time input. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 77

input area transfer of data between main storage and An area of storage reserved for input. peripheral equipment. Synonymous with input block. input-output controller (IOC) input block (ISO) A functional unit in an automatic Synonym for input area. data processing system that controls one or more units of peripheral equipment. input channel Synonymous with I/O controller, peripher¬ A channel for impressing a state on a de¬ al control unit. vice or logic element. Synonymous with input (1). input-output device (ISO) Synonym for input-output unit. input data (1) (ISO) Data being received or to be input-output unit received into a device or into a com¬ (ISO) A device in a data processing sys¬ puter program. Synonymous with in¬ tem by which data may be entered into put (2). the system, received from the system, or (2) Data to be processed. Synonymous both. Synonymous with input-output de¬ with input (1). vice.

input device input process (ISO) Synonym for input unit. (1) (ISO) The process that consists of the reception of dara into a data process¬ input-output (I/O) ing system, into a subsystem, or into (1) (ISO) Pertaining to a device or to a a device. Synonymous with input. channel that may be involved in an (2) The process of transmitting data frojn input process and, at a different time, peripheral equipment, or external stor¬ in an output process. In the English age, to internal storage. language, input-output may be used in (3) The process of receiving data by a place of input-output data, input- device. output signal, input-output terminals, etc., when such usage is clear in a input program given context. (ISO) A utility program that organizes the (2) (ISO) Pertaining to a device whose input process of a computer. parts can be performing an input process and an output process at the input routine same time. (ISO) A utility routine that organizes the (3) Pertaining to either input or output, or input process of a computer. both. (4) (ISO) Synonym for radial transfer. input state The state occurring on a specified input input-output channel channel. (ISO) In an automatic data processing system, a functional unit, controlled by the input station central processing unit, that handles the See data input station. 78 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

input unit unconditional-jump instruction, zero- (ISO) A device in a data processing sys¬ address instruction. tem by which data may be entered into the system. Synonymous with input de¬ instruction address vice. (1) (ISO) The address of an instruction word. inquiry station (2) The address that must be used to (ISO) A user terminal primarily for the fetch an instruction. interrogation of an automatic data process¬ (3) Contrast with address part. ing system. instruction address register

insertion sort (ISO) A register from whose contents the A sort in which each item in a set is in¬ address of the next instruction is derived. An instruction address register may also serted into its proper position in the sort¬ be a portion of a storage device specifi¬ ed set according to the specified criteria. cally designated for the derivation of the address of the next instruction by a tran¬ installation time slator, compiler, interpreter, language Time spent in installing and testing hard¬ processor, operating system, etc. ware or software. Synonymous with control counter, se¬ quence control register. instruction (1) (ISO) In a programming language, a instruction control unit meaningful expression that specifies (ISO) In a central processing unit, the one operation and identifies its ope¬ part that receives instructions in proper rands, if any. sequence, interprets each instruction, and (2) See absolute instruction, arithmetic in¬ applies the proper signals to the arithmet¬ struction, branch instruction, computer ic and logic unit and other parts in ac¬ instruction, conditional jump instruc¬ cordance with this interpretation. tion, direct instruction, discrimination instruction, dummy instruction, effec¬ instruction counter tive instruction, extract instruction, im¬ A counter that indicates the location of mediate instruction, indirect instruction, the next computer instruction to be inter¬ jump instruction, logic instruction, preted. macroinstruction, multiaddress instruc¬

tion, n-address instruction, no-opera¬ instruction format tion instruction, n-plus-one address in¬ (ISO) The layout of an instruction show¬ struction, one-address instruction, one- ing its constituent parts. plus-one address instruction, optional

pause instruction, pause instruction, instruction modifier presumptive instruction, privileged in¬ (ISO) A word or a part of a word that is struction, repetition instruction, restart used to alter an instruction. instruction, stop instruction, three- address instruction, three-plus-one ad¬ instruction register dress instruction, two-address instruc¬ (ISO) A register that is used to hold an tion, two-plus-one address instruction. instruction for interpretation. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 79

instruction repertoire integrating motor (1) A complete set of the operators of the A motor designed to give a constant ratio statements of a computer program¬ of output shaft rotational speed to input ming language, together with a de¬ signal. Thus the angle of rotation of the scription of the types and meanings shaft with respect to a datum is propor¬ that can be attributed to their ope¬ tional to the time integral of the applied rands. signal. (2) Loosely, an instruction set. integrator instruction set (1) A device whose output function is (ISO) The set of the instructions of a proportional to the integral of the in¬ computer, of a programming language, or put function with respect to a speci¬ of the programming languages in a pro¬ fied variable, e.g., a watt-hour meter. gramming system. (2) See incremental integrator.

instruction word interblock gap (ISO) A word that represents an instruc¬ (1) (ISO) A space between blocks on tion. magnetic tape. (2) An area on a data medium used to integer indicate the end of a block or physi¬ (ISO) One of the numbers zero, +1, -1, cal record. +2, -2... Synonymous with integral num¬ (3) Synonymous with block gap. ber. interface integer programming A shared boundary. An interface might (1) (ISO) In operations research, a class be a hardware component to link two de¬ of procedures for locating the max¬ vices or it might be a portion of storage imum or minimum of a function sub¬ or registers accessed by two or more com¬ ject to constraints, where some or all puter programs. variables must have integer values. Synonymous with discrete program¬ interleave ming. To arrange parts of one sequence of (2) Contrast with convex programming, things or events so that they alternate dynamic programming, linear program¬ with parts of one or more other sequences ming, mathematical programming, of things or events and so that each se¬ nonlinear programming, quadratic quence retains its identity. programming. internal sort integral number (1) A sort performed within internal stor¬ (ISO) Synonym for integer. age. (2) A sort program or a sort phase that integrated data processing (IDP) sorts two or more items within main (ISO) Data processing in which the coor¬ storage. dination of data acquisition and other stages of data processing are combined in internal storage a coherent data processing system. (ISO) A storage device directly controlled 80 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

by the central processing unit of a digital inversion computer. (ISO) Deprecated term for negation.

interpret invert (ISO) To translate and to execute each To change a physical or logical state to source language statement of a computer its opposite. program before translating and executing the next statement. inverted file (1) A file whose sequence has been rev¬ interpreter ersed. (1) (ISO) A computer program used to interpret. Synonymous with interpre¬ (2) In information retrieval, a method of tive program. organizing a cross-index file in which (2) (ISO) In punched card operations, a a keyword identifies a record; the device that prints on a punched card items, numbers, or documents perti¬ the characters equivalent to the hole nent to that keyword are indicated. patterns punched in the card.

I/O interpretive code Input-output. The instruction repertoire for the source language input to an interpreter. IOC Input-output controller. interpretive program (ISO) Synonym for interpreter (1). I/O controller

interrecord gap (ISO) Synonym for input-output controller. (ISO) Deprecated term for interblock gap. IFL interrupt Initial program loader. To stop a process in such a way that it

can be resumed. irrational number (ISO) A real number that is not a ration¬ interruption al number. A suspension of a process, such as the execution of a computer program, normal¬ irrelevance ly caused by an event external to that (ISO) In information theory, the condi¬ process, and performed in such a way tional entropy of the occurrence of specific that it can be resumed. messages at a message sink given the oc¬

intersection currences of specific messages at the mes¬ (ISO) Synonym for conjunction. sage source connected to the message sink by a specified channel. If x; is the input

interstage punching message at the message source and yj the A mode of card punching such that the output message at the message sink, the odd or even numbered card columns are irrelevance H(y (x) is expressed by the used. formula: AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 81

item

i=n J=m (1) (ISO) One member of a group. A file H(y]x,= 2 £ Jj, may consist of a number of items M i=i such as records which in turn may

consist of other items. (2) A collection of related characters treat¬ Synonymous with prevarication, spread. ed as a unit.

IS The information separator character.

ISO International Organization for Standardiza¬ tion. 82 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

J

JCL Job control language.

job A set of data that completely defines a jump unit of work for a computer. A job usu¬ (1) (ISO) In the execution of a computer ally includes all necessary computer pro¬ program, a departure from the implicit grams, linkages, files, and instructions to or declared order in which instructions the operating system. are being executed. (2) See conditional jump, unconditional job control language (JCL) jump. A problem-oriented language designed to express statements in a job that are used to identify the job or describe its require¬ jump instruction ments to an operating system. (1) (ISO) An instruction that specifies a jump. job control statement (2) See conditional jump instruction, un¬ A statement in a job that is used to iden¬ conditional jump instruction. tifying the job or describing its require¬ ments to the operating system. justify (1) (ISO) To control the printing positions job step of characters on a page so that both The execution of a computer program ex¬ plicitly identified by a job control state¬ the left-hand and right-hand margins ment. A job may specify that several job of the printing are regular. steps be executed. (2) (ISO) To shift the contents of a register, if necessary, so that the joint information content character at a specified end of the (ISO) In information theory, a measure of data that has been read or loaded in¬ information conveyed by the occurrence of to the register is at a specified posi¬ two events of definite joint probability; in tion in the register. mathematical notation, this measure I(Xj,yj) (3) To align characters horizontally or for two particular events xj7yj from the sets x,...xn and y 1...ym equals the logarithm vertically to fit the positioning con¬ of the reciprocal of the joint probability straints of a required format. P^A)) of the occurrence of both events: (4) See left-justify, right-justify. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 83

K keyboard punch (ISO) Synonym for keypunch.

k An abbreviation for the prefix kilo, i.e., keypunch 1000 in decimal notation. (ISO) A keyboard-actuated device that

punches holes in a punch card or K punched card. Synonymous with key¬ When referring to storage capacity, two to board punch. the tenth power, 1024 in decimal notation.

Karnaugh map key transformation (ISO) A rectangular diagram of a logic A function that maps a set of keys into a function of variables drawn with overlap¬ set of integers, which can be handled ping rectangles representing a unique arithmetically to determine the location of combination of the logic variables and such that an intersection is shown for all the corresponding data elements. combinations.

keyword key (1) One of the predefined words of an (1) (ISO) One or more characters, within artificial language. a set of data, that contains informa¬ (2) (ISO) Deprecated term for reserved tion about the set, including its iden¬ tification. word. (2) See actual key, search key, sort key. (3) Synonym for descriptor. 84 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

L latency (ISO) The time interval between the in¬ stant at which an instruction control unit label initiates a call for data and the instant at (1) (ISO) One or more characters, within which the actual transfer of the data is or attached to a set of data, that con¬ started. Synonymous with waiting time. tains information about the set, includ¬ ing its identification. layout character (2) (ISO) In computer programming, an identifier of an instruction. (ISO) Synonym for format effector.

leader laced card The blank section of tape at the begin¬ A card punched accidentally or intention¬ ally with holes in excess of the hole pat¬ ning of a reel of tape. terns of the character set used. leading decision

lag (1) A loop control that is executed before The delay between two events. the loop body. (2) Contrast with trailing decision.

language (1) (ISO) A set of characters, conventions, leading end and rules, that is used for conveying The end of a perforated tape that first information. The three aspects of lan¬ enters a perforated-tape reader. guage are pragmatics, semantics, and syntax. leading zero (2) See algebraic language, algorithmic In positional notation, a zero in a more language, application-oriented lan¬ significant digit place than the digit place guage, artificial language, assembly of the most significant nonzero digit of a language, command language, comput¬ numeral. er language, computer-oriented lan¬

guage, high-level language, job control leapfrog test language, linear language, machine A check routine that copies itself through language, multidimensional language, storage. natural language, object language, one-dimensional language, problem- left-justify oriented language, procedure-oriented (1) (ISO) To shift the contents of a regis¬ language, programming language, ter, if necessary, so that the character source language, stratified language, syntax language, target language, un- at the left-hand end of the data that strati fied language. has been read or loaded into the reg¬ ister is at a specified position in the

language processor register. (ISO) A computer program that performs (2) (ISO) To control the printing positions such functions as translating and interpret¬ of characters on a page so that the ing and other tasks required for process¬ left-hand margin of the printing is ing a specified programming language. regular. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 85

letter light stability (ISO) A graphic character that, when In optical character recognition, the resist¬ used alone or combined with others, ance to change of the color of the image represents, in a written language, one or when exposed to radiant energy. more sound elements of a spoken lan¬ guage, but excluding diacritical marks line used alone and punctuation marks. See acoustic delay line, character spacing reference line, delay line, electromagnetic

level delay line, flowline, magnetic delay line, (ISO) The degree of subordination of an offline, online, X-datum line, Y-datum item in an hierarchic arrangement. line.

level number linear language A language that is customarily expressed (ISO) A reference number that indicates as a linear representation. For example, the position of an item in a hierarchic ar¬ FORTRAN is a linear language; a flow¬ rangement. Synonymous with rank. chart is not.

LF linear optimization The line feed character. (ISO) Synonym for linear programming.

library linear programming (LP) (1) A collection of related files. For ex¬ (1) (ISO) In operations research, a proce¬ ample, one line of an invoice may dure for locating the maximum or form an item, a complete invoice may minimum of a linear function of vari¬ form a file, the collection of inventory ables that are subject to linear con¬ control files may form a library, and straints. Synonymous with linear op¬ the libraries used by an organization timization. are known as its data bank. (2) Contrast with convex programming, (2) A repository for dismountable record¬ dynamic programming, integer pro¬ ed media, such as magnetic disk packs gramming, mathematical programming, and magnetic tapes. nonlinear programming, quadratic pro¬ (3) See data library, program library. gramming.

library program linear representation (ISO) A computer program in or from a An arrangement of graphics in a one¬ program library. dimensional space.

library routine line-at-a-time printer A proven routine that is maintained in a (ISO) Synonym for line printer. program library. line character LIFO (last-in-first-out) See new-line character. A queuing technique in which the next item to be retrieved is the item most re¬ line feed character (LF) cently placed in the queue. (ISO) A format effector that causes the 86 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

print or display position to move to the list processing corresponding position on the next line. (ISO) A method of processing data in the form of lists. Usually, chained lists are line index used so that the logical order of items See code line index. can be changed without altering their physical locations. line printer

(1) (ISO) A device that prints a line of literal characters as a unit. Synonymous (ISO) In a source program, an explicit re¬ with line-at-a-time printer. presentation of the value of an item, (2) Contrast with character printer, page which value must be unaltered during any printer. translation of the source program, e.g., the word FAIL in the instruction: “IF X = 0 link PRINT FAIL.” (1) (ISO) In computer programming, the part of a computer program, in some load cases a single instruction or an ad¬ (ISO) In computer programming, to enter dress, that passes control and parame¬ data into storage or working registers. ters between separate portions of the computer program. load-and-go (2) (ISO) In computer programming, to An operating technique in which there are provide a link. no stops between the loading and execu¬ (3) (ISO) Synonymous with linkage. tion phases of a computer program, and (4) See data link. which may include assembling or compil¬ ing. linkage (ISO) Synonym for link (1). loaded origin

linkage editor The address of the initial storage location of a computer program in main storage at (1) A utility routine that creates a loada¬ the time the computer program is loaded. ble computer program by combining independently translated computer pro¬ gram modules and by resolving cross loader references among the modules. (1) A routine, commonly a computer pro¬ (2) Contrast with editor program. gram, that reads data into main stor¬ age.

list (2) See absolute loader, bootstrap loader, (1) (ISO) An ordered set of items of initial program loader, relocating load¬ data. er. (2) To print or otherwise display items of data that meet specified criteria. load mode (3) (ISO) Deprecated term for chained (1) In some variable-word-length comput¬ list. ers, data transmission such that certain (4) See chained list, pushdown list, push¬ delimiters are moved with the data. up list. (2) Contrast with move mode. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 87

local (ISO) A logic operation to determine (1) Pertaining to that which is defined whether two strings are identical. and used only in one subdivision of a computer program. logical multiply (2) Contrast with global. (ISO) Synonym for AND.

location logical operation (1) Any place in which data may be (ISO) Synonym for logic operation. stored.

(2) See protected location, storage loca¬ logical product tion. (ISO) Deprecated term for conjunction.

locking logical record (1) (ISO) Of code extension characters, A record independent of its physical envi¬ having the characteristic that change ronment. Portions of the same logical re¬ in interpretation applies to all coded cord may be located in different physical representations following, or to all records, or several logical records or parts coded representations of a given class, of logical records may be located in one until the next appropriate code exten¬ physical record. sion character occurs. (2) Contrast with nonlocking. logical shift (ISO) A shift that equally affects all of logger the characters of a computer word. (1) (ISO) A functional unit that records Synonymous with logic shift. events and physical conditions, usually with respect to time. logical sum (2) A device that enables a user entity to (ISO) Deprecated term for disjunction. log in, e.g., to identify itself, its pur¬ pose and the time of entry; and to logic design log out with the corresponding data A functional design that uses formal so that the appropriate accounting methods of description, such as symbolic procedures may be carried out in ac¬ cordance with the operating system. logic.

logging logic device See data logging. A device that performs logic operations.

logic logic diagram See double rail logic, formal logic, sym¬ A graphic represention of a logic design. bolic logic. logic element logical add (1) A device that performs an elementary (ISO) Synonym for disjunction. logic function. (2) See combinational logic element, se¬ logical comparison quential logic element. 88 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

logic function loop (ISO) Deprecated term for switching func¬ (1) (ISO) A set of instructions that may tion. be executed repeatedly while a certain condition prevails. In some im¬

logic instruction plementations, no test is made to dis¬ cover whether the condition prevails (ISO) An instruction in which the opera¬ until the loop has been executed once. tion part specifies a logic operation. (2) See closed loop, feedback loop, mag¬ netic hysteresis loop. logic operation (1) (ISO) An operation that follows the loop body rules of symbolic logic. (1) The part of a loop that accomplishes (2) (ISO) An operation in which each its primary purpose. character of the result depends on not (2) In a counter, a pan of the loop con¬ more than one character of each ope¬ trol. rand. (3) Contrast with loop control. (3) Synonymous with logical operation,

loop control logic shift (1) The parts of a loop that modify the (ISO) Synonym for logical shift. loop control variables and determine whether to execute the loop body or logic symbol exit from the loop. A symbol that represents an operator, a (2) Contrast with loop body. function or a functional relationship. loop-control variable

logic unit A variable that affects the execution of (1) (ISO) A part of a computer that per¬ instructions in the loop body and is modi¬ fied by a loop control. forms logic operations, and related op¬ erations. loop initialization (2) See arithmetic and logic unit. The parts of a loop that set its starting valued. logic variable (ISO) Deprecated term for switching vari¬ lower curtate able. The adjacent card rows at the bottom of a punch card. longitudinal redundancy check character (LRC) LP On a magnetic tape where each character Linear programming. is represented in a lateral row of bits, a

character used for checking the parity of LRC each track in the longitudinal direction. The longitudinal redundancy check charac¬ Such a character is usually the last ter. character recorded in each block and is

used in some magnetic recording systems Lukasiewicz notation to reestablish the initial recording status. (ISO) Synonym for prefix notation. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 89

M machine word (ISO) Synonym for computer word.

machine macro declaration See accounting machine, electrical account¬ (ISO) Synonym for macro definition. ing machine, turing machine, universal tur-

ing machine. macro definition (ISO) A declaration that provides the ske¬ machine address letal code which a macrogenerator uses in (ISO) Synonym for absolute address (1). replacing a macroinstruction. Synonymous with macro declaration.

machine code (ISO) Synonym for computer instruction macro generating program code. (ISO) Synonym for macrogenerator.

machine instruction macrogenerator (ISO) A computer program that replaces (ISO) Synonym for computer instruction. macroinstructions in the source language with the defined sequence of instructions machine instruction set in the source language. Synonymous with Synonym for computer instruction set. macro generating program.

machine language macroinstruction (1) A language that is used directly by a (ISO) An instruction in a source language machine. that is to be replaced by a defined se¬ (2) (ISO) Deprecated term for computer quence of instructions in the same source instruction code. language. The macroinstruction may also (3) (ISO) Synonym for computer lan¬ specify values for parameters in the in¬ guage. structions that are to replace it.

machine learning macroprogramming (ISO) The ability of a device to improve Computer programming with macroinstruc¬ tions. its performance based on its past perfor¬ mance. magnetic card A card with a magnetic surface on which machine operation data can be stored by magnetic recording. Synonym for computer operation.

magnetic card storage machine-oriented language (ISO) A magnetic storage in which data Synonym for computer-oriented language are stored by selective polarization of por¬ tions of the magnetic material on the sur¬ machine-readable medium face of thin flexible cards. A medium that can convey data to a giv¬

en sensing device. Synonymous with magnetic cell automated data medium. (ISO) A storage cell in which different 90 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

patterns of magnetization are used to magnetic drum represent characters. Synonymous with (ISO) A right circular cylinder with a static magnetic cell. magnetic surface layer.

magnetic core magnetic drum storage (1) (ISO) A piece of magnetic material, (ISO) A magnetic storage in which data usually toroidal in shape, used for are stored by the selective polarization of storage. portions of magnetic material of the (2) A configuration of magnetic material curved surface of a cylinder that rotates that is, or is intended to be, placed in in use. a spatial relationship to current-carry¬ ing conductors and whose magnetic magnetic head properties are essential to its use. It (ISO) An electromagnet that can read, may be used to concentrate an in¬ read or write, write, or erase data on a duced magnetic field as in a trans¬ magnetic data medium. former induction coil, or armature, to

retain a magnetic polarization for the magnetic hysteresis loop purpose of storing data, or for its A closed curve showing the relation be¬ nonlinear properties as in a logic ele¬ tween the magnetization force and the in¬ ment. It may be made of such duction of magnetization in a magnetic material as iron, iron oxide, or ferrite substance when the magnetized field and in such shapes as wires, tapes, to¬ (force) is carried through a complete cy¬ roids, rods, or thin film. cle.

magnetic core storage magnetic ink (ISO) A magnetic storage in which data An ink that contains particles of a mag¬ are stored by the selective polarization of netic substance whose presence can be magnetic cores. detected by magnetic sensors.

magnetic delay line magnetic ink character recognition (MICR) A delay line whose operation is based on (1) Character recognition of characters the time of propagation of magnetic printed with ink that contains particles waves. of a magnetic material. (2) Contrast with optical character recog¬ magnetic disk nition. (ISO) A flat circular plate with a magnet¬ ic surface layer. Synonymous with disk. magnetic recording (ISO) A technique of storing data by se¬

magnetic disk storage lectively magnetizing portions of a mag¬ (ISO) A magnetic storage in which data netizable material. are stored by the selective polarization of portions of magnetic material on the flat magnetic storage surface of one or more disks that rotate A storage device that utilizes the magnetic in use. properties of certain materials. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 91

magnetic tape software. A main control unit at one (1) (ISO) A tape with a magnetic surface time may be a subordinate unit at anoth¬ layer. er time. (2) A tape of magnetic material used as the constituent in some forms of mag¬ main file netic cores. (ISO) Synonym for master file.

magnetic tape storage main frame A magnetic storage in which data are Synonym for central processing unit. stored by the selective polarization of por¬

tions of magnetic material on the surface main storage of a tape that moves longitudinally in use. (ISO) A storage device whose storage cells can be addressed by a computer pro¬ magnetic tape unit gram and from which instructions and (ISO) A device containing a tape drive, data can be loaded directly into registers together with read heads, write heads and from which the instructions can be execut¬ associated controls. ed or from which the data can be operat¬ ed upon. magnetic thin film A layer of magnetic material, usually less maintainability than one micron thick, often used for log¬ (ISO) The ease with which maintenance ic elements or storage elements. of a functional unit can be performed in accordance with prescribed requirements. magnetic thin film storage (ISO) A magnetic storage in which the maintenance data are stored by the selective polariza¬ (1) (ISO) Any activity, such as tests, tion of portions of a magnetic film of measurements, replacements, adjust¬ molecular thickness, coated on a substrate. ments, and repairs, intended to elimi¬ nate faults or to keep a functional magnetic track unit in a specified state. (ISO) A track on the surface layer of a (2) See corrective maintenance, deferred magnetic storage. maintenance, emergency maintenance, file maintenance, preventive mainte¬ magnetic wire storage nance, scheduled maintenance. (ISO) A magnetic storage in which data are stored by selective magnetization of maintenance panel portions of a wire. A part of a unit of equipment that is used for interaction between the unit of

main control unit equipment and a maintenance engineer. (ISO) In a computer with more than one instruction control unit, that instruction maintenance time control unit to which, for a given interval (1) Time used for hardware maintenance. of time, the other instruction control units It includes preventive maintenance are subordinated. An instruction control time and corrective maintenance time. umt may be designated as the main con¬ (2) Contrast with available time. trol unit by hardware or by hardware and (3) See corrective maintenance time, de- 92 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

ferred maintenance time, emergency See algebraic manipulation, formula maintenance time, preventive mainte¬ mampulation, symbol manipulation. nance time. mantissa majority (1) (ISO) The positive fractional part of A logic operator having the property that the representation of a logarithm. In if P is a statement, Q is a statement, R is the expression, log 643 = 2.808, the a statement,..., then the majority of P, Q, .808 is the mantissa and the 2 is the R, ..., is true if more than half the state¬ characteristic. ments are true, false if half or less are (2) (ISO) Synonym for fixed-point part. true. (3) Contrast with characteristic.

majority element manual input A logic element that performs a majority (1) The entry of data by hand into a de¬ operation. Synonymous with majority vice. gate. (2) The data entered as in (1).

majority gate map Synonym for majority element. (1) (ISO) To establish a set of values having a defined correspondence with majority operation the quantities or values of another set. (ISO) A threshold operation in which Synonymous with map over. each of the operands may take only the (2) See Karnaugh map. values zero and one, and that takes the value one if and only if the number of map over operands having the value one is greater (ISO) Synonym for map. than half the total number of operands. marginal check makeup time Synonym for marginal test. (1) (ISO) That part of available time used for reruns due to faults or mis¬ marginal test takes in operating. Maintenance in which certain operating (2) Contrast with development time. conditions, such as voltage or frequency supplied, are varied about their nominal malfunction values in order to detect and locate com¬ (ISO) Synonym for failure. ponents with incipient faults. Synonymous with marginal check. management information system (MIS) (1) (ISO) Management performed with mark the aid of automatic data processing. (1) (ISO) A symbol or symbols that indi¬ (2) An information system designed to aid cate the beginning or the end of a in the performance of management field, of a word, of an item of data functions. or of a set of data such as a file, a record, or a block. manipulation (2) See document mark, group mark, AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 93

marker master file See end-of-tape marker. (ISO) A file that is used as an authority in a given job and that is relatively per¬ Markov chain manent, even though its contents may A probabilistic model of events in which change. Synonymous with main file. the probability of an event is dependent only on the event that precedes it. match (1) A comparison to determine identity of mark sensing items. (1) The electrical sensing of manually (2) Contrast with hit. recorded conductive marks on a non- conductive surface. mathematical check (2) The automatic sensing of manually A programmed check that uses math¬ recorded marks on a data medium. ematical relationships. Synonymous with arithmetic check. mark-sensing card A card on which mark-sensible fields have mathematical induction been printed. (ISO) A method of proving a statement concerning terms based on natural num¬ mark-sensing column bers not less than N by showing that the A line of mark-sensible positions, parallel statement is valid for the term based on to the Y-datum line of a card. N and that, if it is valid for an arbitrary value of n that is greater than N, it is mark-sensing row also valid for the term based on (n + 1). A line of mark-sensible positions parallel to the A'-datum line of a card. mathematical logic (ISO) Synonym for symbolic logic. mask (1) (ISO) A pattern of characters that is mathematical model used to control the retention or elimi¬ A mathematical representation of a nation of portions of another pattern process, device, or concept. of characters. (2) (ISO) To use a pattern of characters mathematical programming to control the retention or elimination (1) (ISO) In operations research, a proce¬ of portions of another pattern of dure for locating the maximum or characters. minimum of a function subject to con¬ straints. mass storage (2) Contrast with convex programming, (ISO) An auxiliary storage of very large dynamic programming, integer pro¬ storage capacity used for storage of data gramming, linear programming, non¬ to which infrequent reference need be linear programming, quadratic pro¬ made. Synonymous with bulk storage. gramming.

mass storage device matrix A device having a large storage capacity, (1) (ISO) A rectangular array of elements, e.g., magnetic disk, magnetic drum. arranged in rows and columns, that 94 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

may be mampulated according to the mean transinformation content rules of matrix algebra. (1) (ISO) In information theory, the mean (2) In computers, a logic network in the of the transformation content conveyed form of an array of input leads and by the occurrence of any one of a Fi¬ output leads with logic elements con¬ nite number of mutually exclusive and nected at some of their intersections. jointly exhaustive events, given the oc¬ (3) By extension, an array of any number currence of another set of mutually of dimensions. exclusive events; in mathematical nota¬ tion, the mean transinformation con¬ (4) See dot matrix. tent, T, for a set of events x,...xn which are dependent on the occur¬ matrix printer rence of events from another set (ISO) A printer in which each character is y,...ym with joint probabilities p(X;,ya) represented by a pattern of dots. of the occurrence of both events x;, y., Synonymous with dot printer, stylus print¬ equals the mathematical expectation of er, wire printer. the transinformation content T(Xj |y.) of all pairs of events: matrix storage Storage, the elements of which are ar¬ ranged such that access to any location n m requires the use of two or more coordi¬ T= 2 5Z PtXi'Yj) T (xi 1 Vj) nates, e.g., cathode ray storage, magnetic i=1 j=1 core storage.

mean conditional information content The mean transinformation content (ISO) Synonym for conditional entropy. also is equal to the difference between the entropy of one of the two sets of mean entropy events and the conditional entropy of See character mean entropy. this set relative to the other. For in¬ stance, in transmitting one message, mean information content the difference between the entropy at (ISO) Synonym for entropy. the message source and the equivoca¬ tion, and the difference between the mean repair time entropy at the message sink and the (ISO) Deprecated term for mean-time- irrelevance are equal, i.e.: to-repair.

mean-time-between-failures (MTBF) (ISO) For a stated period in the life of a T = H (x) — H(x\y) = H(y) - H(y\n) functional unit, the mean value of the lengths of time between consecutive fail¬ ures under stated conditions.

Synonymous with average transinfor¬ mean-time-to-repair (MTTR) mation content. (ISO) The average time required for cor¬ (2) See character mean transinformation rective maintenance. content. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 95

measure of information dered series of characters intended to See information measure. convey information. (3) See error message. medium See data medium, empty medium, ma¬ message sink chine readable medium, virgin medium. (ISO) That part of a communication sys¬ tem in which messages are considered to member be received. (ISO) Synonym for element. message source memory (ISO) That part of a communication sys¬ (ISO) Deprecated term for main storage. tem from which messages are considered to originate. Synonymous with informa¬ memory protection tion source. Deprecated term for storage protection. metalanguage mercury storage A language used to specify itself, or other A storage device that utilizes the acoustic languages. properties of mercury to store data. MICR merge Magnetic ink character recognition. (1) (ISO) To combine the items of two or more sets that are each in the same microfiche given order into one set in that order. A sheet of microfilm capable of contain¬ (2) See balanced merge. ing microimages in a grid pattern, usually (3) See also collate. containing a title that can be read without magnification. merge sort (1) A sort program in which the items in microfilm a set are divided into subsets, the (1) A high resolution film for recording items in each subset are sorted, and microimages. the resulting sorted subsets are (2) To record microimages on film. merged. (3) See computer output microfilm. (2) See balanced merge sort, unbalanced merge sort. microfilmer See computer output microfilmer. merging See order-by-merging, sequence-by-merg- microform ing. Any medium that contains microimages.

message micrographics (1) An arbitrary amount of information That branch of science and technology whose beginning and end are defined concerned with methods and techniques or implied. for converting any form of information to (2) (ISO) In information theory, an or¬ or from microform. 96 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

microimage mixed-base notation An image too small to read without mag¬ (ISO) Synonym for mixed-base numeration nification. system.

microprogram mixed-base numeration system (ISO) A sequence of elementary instruc¬ (1) (ISO) A numeration system in which tions that correspond to a computer oper¬ a number is represented as the sum ation, that is maintained in special stor¬ of a series of terms each of which age, and whose execution is initiated by consists of a mantissa and a base, the the introduction of a computer instruction base of a given term being constant into an instruction register of a computer. for a given application but the bases being such that there are not neces¬ microprogramming sarily integral ratios between the bases (ISO) The preparation or use of micropro¬ of all the terms, e.g., with bases b3, grams. b2, and b, and mantissae 6, 5, and 4, the number represented is given by minimum delay programming 6b3 + 5b2 + 4b,. A mixed-radix nu¬ (ISO) A method of programming in meration system is the particular case which storage locations for instructions of a mixed-base numeration system in and data are chosen so that access time is which, when the terms are ordered so reduced and minimized. that their bases are in descending magnitudes, there is an integral ratio minimum distance code between the bases of adjacent terms, A binary code in which the signal dis¬ but not the same ratio in each case; tance does not fall below a specified thus if the smallest base is b and if x minimum value. and y represent integers, the numeral 654 in such a numeration system minuend represents the number given by 6 xyb (ISO) In subtraction, the number or quan¬ -I- 5 xb + 4 b. A fixed-radix numer¬ tity from which another number or quan¬ tity is subtracted. ation system is the particular case of a mixed-base numeration system in

MIS which, when the terms are ordered so Management information system. that their bases are in descending magnitudes, there is the same integral

miscellaneous time ratio between bases of all pairs of ad¬ (ISO) The time during which a computer jacent terms; thus if b is the smallest is used for demonstrations, training, or base and if x represents an integer, other such purposes. Synonymous with the numeral 654 in such a numeration incidental time. system represents the number given by 6 x2b + 5 xb + 4 b. Synonymous mistake with mixed-base notation. (1) A human action that produces an (2) Contrast with mixed-radix numeration unintended result. system. (2) Contrast with error, failure, fault, mal¬ function. mixed-radix notation AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 97

(ISO) Synonym for mixed-radix numera¬ modularity tion system. The extent to which a system is composed of modules. mixed-radix numeration system (1) (ISO) A radix numeration system in modulator-demodulator which the digit places do not all See modem. necessarily have the same radix, e.g., the numeration system in which three module successive digits represent hours, tens (1) A program unit that is discrete and of minutes, and minutes; taking one identifiable with respect to compiling, minute as the unit, the weights of the combining with other units, and load¬ three digit places are 60, 10 and 1 re¬ ing, e.g., the input to, or output from, spectively; the radices of the second an assembler, compiler, linkage editor, and third digit places are 6 and 10 or executive routine. respectively. A comparable numera¬ (2) A packaged functional hardware unit tion system that used one or more di¬ designed for use with other compo¬ gits to represent days and two digits nents. to represent hours would not satisfy (3) See object module, programming the definition of any radix numeration module. system, since the ratio of the weights of the “days” and the “tens of modulo-n check hours” digit places would not be an Synonym for residue check. integer. Synonymous with mixed-radix

notation. modulo-n counter (2) Contrast with mixed-base numeration (ISO) A counter in which the number system. represented reverts to zero in the sequence of counting after reaching a maximum va¬ mnemonic symbol lue of n - 1. (ISO) A symbol chosen to assist the hu¬ man memory, e.g., an abbreviation such modulo-two sum as “mpy” for “multiply.” (ISO) Deprecated term for nonequivalence operation. mode See access mode, conversational mode, monadic boolean operator load mode, move mode. A boolean operator having only one ope¬ rand, e.g., NOT. model See mathematical model. monadic operation (ISO) An operation with one and only modem (Modulator-demodulator) one operand. Synonymous with unary op¬ A device that modulates and demodulates eration. signals transmitted over data communica¬ tion facilities. monadic operator (ISO) An operator that represents an op¬ modifier register eration on one and only one operand. (ISO) Synonym for index register. Synonymous with unary operator. 98 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

monitor move mode (1) (ISO) A device that observes and (1) In some variable-word-length comput¬ verifies the operations of a data proc¬ ers, data transmission such that certain essing system and indicates any sig¬ delimiters are not moved with the nificant departure from the norm. data. (2) Software or hardware that observes, (2) Contrast with load mode. supervises, controls, or verifies the op¬ MTBF erations of a system. Mean-time-between-failures.

monitoring program MTTR (ISO) Synonym for monitor program. Mean-time-to-repair.

monitor program multiaddress (ISO) A computer program that observes, Pertaining to an instruction format con¬ regulates, controls, or verifies the opera¬ taining more than one address part. tions of a data processing system. Synonymous with monitoring program. multiaddress instruction (ISO) An instruction that contains more monostable than one address part. Synonymous with Pertaining to a device that has one stable multiple address instruction. state.

multi-aperture core monostable circuit (ISO) A magnetic core, usually used for A trigger circuit that has one stable state nondestructive reading, with two or more and one unstable state. Synonymous with holes through which wires may be passed monostable trigger circuit. in order to create more than one magnetic path. Synonymous with multiple aperture monostabie trigger circuit core. Synonym for monostable circuit.

multidimensional language Monte Carlo method (1) A language whose expressions are as¬ (ISO) A method of obtaining an approxi¬ sembled in more than one dimension, mate solution to a numerical problem by e.g., flowcharts, logic diagrams, block the use of random numbers, e.g., the ran¬ diagrams, and decision tables. dom walk method, or a procedure using a (2) Contrast with one-dimensional lan¬ random number sequence to calculate an guage. integral. multilevel address move (ISO) Synonym for indirect address. (1) (ISO) In computer programming, to copy from locations in internal storage multipass sort into locations in the same internal A sort program that is designed to sort storage. more items than can be in main storage (2) (ISO) Synonym for transfer. at one time. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 99

multiple address instruction (3) See quarter squares multiplier. (ISO) Synonym for multiaddress instruc¬ tion. multiplier factor (ISO) In a multiplication operation, the multiple aperture core factor by which the multiplicand is multi¬ (ISO) Synonym for multi-apenure core. plied. Synonymous with multiplier.

multiple precision multiply (ISO) Pertaining to the use of two or See logical multiply. more computer words to represent a num¬

ber in order to enhance precision. multiplying punch (ISO) Synonym for calculating punch. multiple punching

The punching of more than one hole in multiprocessing the same card column by means of more (1) A mode of operating a multiprocessor than one keystroke, usually in order to that provides for the parallel process¬ extend the character set of the punch. ing of two or more computer pro¬ grams. multiplex (2) Pertaining to the simultaneous execu¬ To interleave or simultaneously transmit tion of two or more computer pro¬ two or more messages on a single chan¬ grams or sequences of instructions by nel. a computer or computer network. (3) Loosely, parallel processing. multiplexer A device capable of interleaving the multiprocessor events of two or more activities or capa¬ A computer employing two or more cen¬ ble of distributing the events of an inter¬ tral processing units under integrated con¬ leaved sequence to the respective activities. trol.

multiplex operation multiprogramming A mode of operation in which the events (1) A mode of operation that provides for of two or more activities are interleaved the interleaved execution of two 01 and when required the events in the inter¬ leaved sequence are distributed to the re¬ more computer programs by a single spective activities. central processing unit. (2) Pertaining to the concurrent execution

multiplicand of two or more computer programs by (ISO) In a multiplication operation, the a computer. factor that is multiplied by another num¬ ber or quantity. multitasking Pertaining to the concurrent execution of

multiplier two or more tasks by a computer. (1) (ISO) In multiplication, the number or quantity by which the multiplicand is mutual information multiplied. (ISO) Synonym for transinformation con¬ (2) (ISO) Synonym for multiplier factor. tent. 100 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

N n-ary boolean operation (ISO) Deprecated term for n-adic boolean operation. e-address Instruction (ISO) An instruction that contains n ad¬ n-ary operation dress parts. (ISO) Synonym for n-adic operation.

n-adic boolean operation (ISO) A boolean operation on n and only NAT n operands. (ISO) Information content natural unit.

n-adic operation natural language (ISO) An operation on n and only n ope¬ (1) (ISO) A language whose rules are rands. Synonymous with n-ary operation. based on current usage without being explicitly prescribed. NA& (2) Contrast with artificial language. The negative acknowledge character.

natural number name (ISO) One of the numbers zero, 1, 2, ... See data name, qualified name. Synonymous with nonnegative number.

NAND n-bit byte A logic operator having the property that (ISO) A byte composed of n binary ele¬ if P is a statement, Q is a statement, R is a statement,...,then the NAND of P, Q, ments. R,... is true if at least one statement is false, false if all statements are true. Sy¬ n-core-per-bit storage nonymous with nonconjunction, NOT- (ISO) A storage device in which each AND, Sheffer stroke. storage cell uses n magnetic cores per bi- naiy character. NAND element A logic element that performs the boolean NDM operation of nonconjunction. Synonymous (ISO) Nondestructive read. with NAND gate.

NDRO NAND gate (ISO) Nondestructive readout. Synonym for NAND element.

needle NAND operation A probe in a manual information retrieval (ISO) Synonym for nonconjunction. operation that may be passed through

n-ary holes or notches to assist in sorting or (1) (ISO) Pertaining to a selection, choice, selecting cards. or condition that has n possible differ¬ ent values or states. negate (2) (ISO) Pertaining to a fixed-radix nu¬ (1) (ISO) To perform the operation of meration system having a radix of n. negation. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 101

(2) To perform the logic operation NOT. A device that simulates a network such as an electrical supply network. negation (ISO) The monadic boolean operation the new-line character (NL) result of which has the boolean value op¬ (1) (ISO) A format effector that causes posite to that of the operand. the print or display position to move Synonymous with NOT operation. to the First position on the next line. (2) Contrast with carriage return character. negative acknowledge character (NAK) (ISO) A transmission control character nines complement transmitted by a station as a negative re¬ (ISO) The diminished radix complement sponse to the station with which the con¬ in the decimal numeration system. Sy¬ nection has been set up. nonymous with complement-on-nine.

negentropy NL (ISO) Deprecated term for entropy. The new line character.

neither-nor operation n-level address An indirect address that specifies n levels (ISO) Synonym for nondisjunction. of addressing.

nest node (1) (ISO) To incorporate a structure or (1) The representation of a state or an structures of some kind into a struc¬ event by means of a point on a dia¬ ture of the same kind. For example, gram. to nest one loop (the nested loop) (2) In a tree structure, a point at which within another loop (the nesting subordinate items of data originate. loop); to nest one subroutine (the nested subroutine) within another sub¬ noise routine (the nesting subroutine). (1) Random variations of one or more (2) To embed subroutines or data in oth¬ characteristics of any entity such as er subroutines or data at a different voltage, current, or data. hierarchical level such that the differ¬ (2) A random signal of known statistical ent levels of routines or data can be properties of amplitude, distribution, or accessed recursively. executed and spectral density. (3) Loosely, any disturbance tending to network interfere with the normal operation of See computer network. a device or system.

network analog nonconjunction The expression and solution of mathemati¬ (1) (ISO) The dyadic boolean operation cal relationships between variables using a the result of which has the boolean circuit or circuits to represent these varia¬ value 0 if and only if each operand bles. has the boolean value 1. Synonymous with NAND, NAND operation, NOT network analyzer BOTH operation. 102 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(2) Contrast with conjunction. dure for locating the maximum or minimum of a function of variables nondestructive read (NDR) that are subject to constraints, when (ISO) A read process that does not erase either the function or the constraints, the data in the source. Synonymous with or both, are nonlinear. Synonymous nondestructive readout. with nonlinear optimization. (2) Contrast with convex programming, nondestructive readout (NDRO) dynamic programming, integer pro¬ (ISO) Synonym for nondestructive read. gramming, linear programming, math¬ ematical programming, quadratic pro¬ nondisjunction gramming. (1) (ISO) The dyadic boolean operation the result of which has the boolean nonlocking value 1 if and only if each operand (1) (ISO) Of code extension characters, has the boolean value 0. Synonymous having the characteristic that the with neither-nor operation, nor opera¬ change in interpretation applies only tion. to a specified number of the coded (2) Contrast with disjunction. representations following, commonly only one. nonequivalence operation (2) Contrast with locking. (1) (ISO) The dyadic boolean operation the result of which has the boolean nonnegative number value 1 if and only if the operands (ISO) Synonym for natural number. have diffent boolean values. Synonymous with exclusive-OR opera¬ non-polarized return-to-zero recording tion. (RZ(NP)) (2) Contrast with equivalence operation. Retum-to-reference recording in which zeros are represented by the absence of nonerasable storage magnetization, ones are represented by a (ISO) Synonym for fixed storage. specified condition of magnetization, and the reference condition is zero magnetiza¬ nonidentity operation tion. The specified condition is usually (1) (ISO) The boolean operation the re¬ saturation. Conversely, the absence of sult of which has the boolean value 1 magnetization can be used to represent if and only if all the operands do not ones, and the magnetized condition to have the same boolean value. A represent zeros. Synonymous with dipole nonidentity operation on two operands modulation. is a nonequivalence operation. (2) Contrast with identity operation. non-return-to-change recording A method of recording in which ones are nonlinear optimization represented by a specified condition of (ISO) Synonym for nonlinear program¬ magnetization and zeros are represented ming. by a different condition.

nonlinear programming non-return-to-reference recording (1) (ISO) In operations research, a proce¬ The magnetic recording of bits in which AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 103

the patterns of magnetization used to no-op represent zeros and ones occupy the whole (ISO) No-operation instmction. storage cell, with no part of the cell mag¬ netized to a reference condition. no-operation instruction (ISO) An instruction whose execution non-return-to-zero change-on-ones recording causes a computer to do nothing other (NRZI) than to proceed to the next instruction to Non-retum-to-reference recording in which be executed. Synonymous with do-nothing ones are represented by a change in the operation. condition of magnetization, and zeros are represented by the absence of a change. NOR This method is called NRZ (mark) A logic operator having the property that recording because only the one or mark if P is a statement, Q is a statement, R is signals are explicitly recorded. a statement,..., then the NOR of P, Q, Synonymous with non-retum-to-zero R,... is true if all statements are false, (mark) recording, NRZ(M). false if at least one statement is true. P NOR Q is often represented by a combi¬ non-return-to-zero (change) recording nation of OR and NOT symbols, such as (NRZ(C)) ~(PAQ). P NOR Q is also called neither Non-retum-to-reference recording in which P nor Q. Synonymous with NOT-OR. zeros are represented by magnetization to a specified condition, and ones are repre¬ NOR element sented by magnetization to a specified al¬ A logic element that performs the boolean ternative condition. The two conditions operation of nondisjunction. Synonymous may be saturation and zero magnetization with NOR gate. but are more commonly saturation in op¬ posite senses. This method is called NRZ NOR gate (change) recording because the recorded Synonym for NOR element. magnetic condition is changed when, and only when, the recorded bit changes from zero to one or from one to zero. normal direction flow (ISO) A flow direction from left to right

non-return-to-zero (mark) recording or top to bottom on a flowchart. (NRZ(M)) Synonym for non-retum-to-zero change- normalize on-ones recording. (1) (ISO) to make an adjustment to the fixed-point part and the corresponding non-return-to-zero recording (NRZ) adjustment to the exponent in a Non-retum-to-reference recording in which floating-point representation to ensure the reference condition is zero magnetiza¬ that the fixed-point part lies within tion. some prescribed range, the real num¬ ber represented remaining unchanged. non-volatile storage Synonymous with standardize. (ISO) A storage whose content is not lost (2) Loosely, to scale. when the power is removed. (3) (ISO) Deprecated term for scale. 104 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

normalized form NOT-IF-THEN element (ISO) The form taken by a floating-point A logic element that performs the boolean representation when the fixed-point part operation of exclusion. Synonymous with lies within some prescribed standard NOT-IF-THEN gate. range, so chosen that any given real num¬ ber is represented by a unique pair of nu¬ NOT-IF-THEN gate merals. Synonymous with standard form. Synonym for NOT-IF-THEN element.

NOR operation NOT-IF-THEN operation (ISO) Synonym for nondisjunction. (ISO) Synonym for exclusion.

NOT NOT operation (ISO) Synonym for negation. A logic operator having the property that if P is a statement, then the NOT of P is NOT-OR true if P is false, false if P is true. The Synonym for NOR. NOT of P is often represented by P, ~P, ~1 P, P'. NOT-OR operation (ISO) Deprecated term for nondisjunction.

noughts complement NOT-AND (ISO) Synonym for radix complement. Synonym for NAND.

n-plus-one address instruction NOT AND operation (ISO) An instruction that contains n + 1 (ISO) Deprecated term for nonconjunction. address parts, the plus-one address being that of the instruction that is to be ex¬ notation ecuted next unless otherwise specified. (1) (ISO) A set of symbols, and the rules for their use, for the representation of NRZ data. Non-retum-to-zero recording. (2) See binary notation, decimal notation,

infix notation, parentheses-free nota¬ NRZ(C) tion, postfix notation, prefix notation. Non-retum-to-zero (change) recording.

NOT BOTH operation NRZI (ISO) Synonym for nonconjunction. Non-retum-to-zero change-on-ones record¬ ing. NOT element A logic element that performs the boolean NRZ(M) operation of negation. Synonymous with Non-retum-to-zero (mark) recording. NOT gate. n-tupie length register NOT gate (ISO) N registers logically or physically Synonym for NOT element. connected to function as a single register. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 105

Each register may be individually ac¬ number sequence cessed. Synonymous with n-tuple register. See pseudo-random number sequence, ran¬ dom number sequence. n-tuple register (ISO) Synonym for n-tuple length register. number system (ISO) Deprecated term for numeration NUL system. The null character. numeral null character (NUL) (1) (ISO) A discrete representation of a (1) (ISO) A control character that is used number. The following are four differ¬ to to accomplish media-fill or time-fill ent numerals that represent the same and that may be inserted into or number, i.e., a dozen, in the methods removed from a sequence of charac¬ shown: twelve, by a word in the Eng¬ ters without affecting the meaning of lish language; 12, in the decimal nu¬ the sequence; however, the control of meration system; XII by Roman nu¬ equipment or the format may be af¬ merals; 1100 in the pure binary nu¬ fected by this character. meration system. (2) See also space character. (2) See binary numeral, decimal numeral.

null set numeration (ISO) Synonym for empty set. (ISO) Synonym for number representation.

null string numeration system (1) (ISO) A string containing no entity. (1) (ISO) Any notation for the representa¬ (2) The notion of a string depleted of its tion of numbers. Synonymous with entities, or the notion of a string prior number representation system. to establishing its entities. (2) See decimal numeration system, fixed- radix numeration system, mixed-base number numeration system, mixed-radix nu¬ (1) A mathematical entity that may indi¬ meration system, pure binary numera¬ cate quantity or amount of units. tion system, radix numeration system. (2) Loosely, a numeral. (3) See binary number, complex number, numeric Fibonacci number, irrational number, (ISO) Pertaining to data or to physical level number, natural number, random quantities represented by numerals. Sy¬ number, rational number, serial num¬ nonymous with numerical. ber. numerical number representation (ISO) Synonym for numeric. (ISO) A representation of a number in a numeration system. Synonymous with nu¬ numerical analysis meration. The study of methods of obtaining useful quantitative solutions to problems that number representation system have been expressed mathematically, in¬ (ISO) Synonym for numeration system. cluding the study of the errors and 106 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

bounds on errors in obtaining such solu¬ (ISO) A coded character set whose tions. character set is a numeric character set.

numerical control (NC, NCMT) numeric data (ISO) Automatic control of a process per¬ (1) (ISO) Data represented by numerals. formed by a device that makes use of (2) Data represented by numerals and numerical data usually introduced as the operation is in progress. some special characters.

numeric character numeric punch (ISO) Synonym for digit (1). A hole punched in one of the punch rows designated as zero through nine. A zero- numeric character set punch, and sometimes an eight- or nine- (ISO) A character set that contains digits punch, in combination with another nu¬ and may contain control characters, spe¬ meric punch, is considered a zone punch. cial characters, and the space character, but not letters. numeric representation numeric character subset (ISO) A discrete representation of data by (ISO) A character subset that contains di¬ numerals. gits and may contain control characters, special characters, and the space character, numeric word but not letters. (ISO) A word consisting of digits and possibly space characters and special numeric code (ISO) A code according to which data is characters. For example, in the Universal represented by a numeric character set. Decimal Classification system, the numeric word 61(03)=20 is used as an identifier numeric coded character set for any medical encyclopedia in English. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 107

0 one-address instruction (ISO) An instruction that contains one ad¬ dress part. object code Output from a compiler or assembler one-ahead addressing which is itself executable machine code or A method of implied addressing in which is suitable for processing to produce ex¬ the operation part of an instruction implic¬ ecutable machine code. itly addresses the operands in the location following the location of the operands of object language (1) (ISO) A language that is specified by the last instruction executed. a metalanguage. (2) (ISO) Synonym for target language. one-core-per-bit storage (ISO) A storage device in which each

object module storage cell uses one magnetic core per A module that is the output of an assem¬ binary character. bler or compiler and is input to a linkage editor. one-dimensional language (1) A language whose expressions are cus¬ object program tomarily represented as strings of (1) (ISO) A fully compiled or assembled characters, e.g., FORTRAN. program that is ready to be loaded (2) Contrast with multi-dimensional lan¬ into the computer. guage. (2) Synonym for target program.

(3) Contrast with source program. one-level address (ISO) Synonym for direct addess. OCR

Optical character recognition. one-plus-one address instruction (ISO) An instruction that contains two ad¬ octal dress parts, the plus one address being (ISO) Pertaining to a fixed-radix numera¬ that of the instruction that is to be ex¬ tion system having a radix of eight. ecuted next unless otherwise specified.

octet ones complement (ISO) A byte composed of eight binary (ISO) The diminished radix complement elements. in the pure binary numeration system. Synonymous with complement-on-one. odd-even check Synonym for parity check. online (1) Pertaining to equipment or devices un¬ offline Pertaining to equipment or devices not der the direct control of a central under control of a central processing unit. processing unit. (2) Pertaining to a user’s ability to in¬

offline storage teract with a computer. Storage not under control of the central (3) Pertaining to the user’s access to a processing unit. computer via a terminal. 108 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

online storage assignment, data management, and related Storage under control of the central proc¬ services. essing unit. operating time on-lhe-fly printer (1) That part of available time during (ISO) An impact printer in which the which the hardware is operating and type slugs do not stop moving during the is assumed to be yielding correct impression time. Synonymous with hit- results. It includes program develop¬ on-the-fly printer. ment time, production time, makeup time, and miscellaneous time. open-ended (2) Contrast with idle time. Pertaining to a process or system that can be augmented. operation (1) (ISO) A well-defined action that, open shop when applied to any permissible (1) Pertaining to the operation of a com¬ combination of known entities, puter facility in which most productive produces a new entity. problem programming is performed by (2) A defined action, namely, the act of the problem originator rather than by obtaining a result from one or more a group of programming specialists. operands in accordance with a rule The use of the computer itself may that completely specifies the result for also be described as open shop if the any permissible combination of ope¬ user/programmer also serves as the rands. operator. (3) A program step undertaken or execut¬ (2) Contrast with closed shop. ed by a computer, e.g., addition, multiplication, extraction, comparison, open subroutine shift, transfer. The operation is usual¬ (1) (ISO) A subroutine of which a replica ly specified by the operator part of an must be inserted at each place in a instruction. computer program at which the sub¬ (4) The event or specific action performed routine is used. Synonymous with di¬ by a logic element. rect insert subroutine. (5) See arithmetic operation, asynchronous (2) Contrast with closed subroutine. operation, auxiliary operation, binary arithmetic operation, boolean opera¬ operand tion, complementary operation, com¬ (1) (ISO) An entity to which an operation puter operation, concurrent operation, is applied. control operation, dual operation, dya¬ (2) That which is operated upon. An dic boolean operation, dyadic opera¬ operand is usually identified by an tion, equivalence operation, fixed-cycle address part of an instruction. operation, identity operation, logic op¬ eration, majority operation, monadic operating system operation, multiplex operation, n-adic (ISO) Software that controls the execution boolean operation, n-adic operation, of computer programs and that may pro¬ non-equivalence operation, non-identity vide scheduling, debugging, input-output operation, parallel operation, sequential control, accounting, compilation, storage operation, serial operation, simultane- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 109

ous operation, single-step operation, (4) See boolean operator, complementary threshold operation. operator, dyadic operator, monadic boolean operator, monadic operator, operation code quaternary operator, unary operator. (ISO) A code used to represent the opera¬ tions of a computer. operator console (ISO) A functional unit containing devices operation decoder that are used for communication between A device that selects one or more control a computer operator and an automatic channels according to the operation part data processing system. of a machine instruction. operator control panel operation part (ISO) A part of an operator console, of a (ISO) A part of an instruction that usual¬ computer, or of an automatic data proc¬ ly contains only an explicit specification of essing system that contains switches used the operation to be performed. For an to control the system or part of the sys¬ exception to “usually,” see implied ad¬ tem and that may contain indicators giv¬ dressing. Synonymous with function part, ing information on the functioning of the operator part. system or of part of the system.

operations analysis operator part (ISO) Synonym for operations research. (ISO) Synonym for operation part.

operations research (OR) optical character recognition (OCR) (ISO) The application of scientific meth¬ (1) The machine identification of printed ods to the solution of complex problems characters through use of light sensi¬ concerning the optimal allocation of avail¬ tive devices. able resources. Synonymous with opera¬ (2) Contrast with magnetic ink character tions analysis. recognition.

operation table optical scanner (1) (ISO) A table that defines an opera¬ (1) (ISO) A scanner that uses light for tion by listing all permissible combina¬ examining patterns. tions of values of the operands and (2) A device that scans optically and usu¬ indicating the result for each of these ally generates an analog or digital sig¬ combinations. nal. (2) See boolean operation table. optional pause instruction operator (ISO) An instruction that allows manual (1) (ISO) A symbol that represents the suspension of the execution of a computer action to be performed in a math¬ program. Synonymous with optional stop ematical operation. instruction. (2) In the description of a process, that which indicates the action to be per¬ optional-stop instruction formed on operands. (ISO) Synonym for optional pause instruc¬ (3) A person who operates a machine. tion. 110 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

OR OR operation (1) A logic operator having the property Synonym for disjunction. that if P is a statement, Q is a state¬ ment, R is a statement,... then the OR oscillating sort of P, Q, R,..., is true if at least one A merge sort in which f e sorts and statement is true, false if all state¬ merges are performed alternately to form ments are false. P OR Q is often one sorted set. represented by P + Q, PVQ. Synony¬ mous with boolean add. outconnector (2) Contrast with exclusive OR. (1) In flowcharting, a connector that indi¬ (3) Operations research. cates a point at which a flowline is broken for continuation at another

order point. (2) Contrast with inconnector. (1) (ISO) A specified arrangement used in ordering. An order need not be linear. output (2) An arrangement of items according to (1) (ISO) Pertaining to a device, process, any specified set of rules. or channel involved in an output (3) (ISO) To place items in an arrange¬ process, or to the data or states in¬ ment in accordance with specified volved in an output process. rules. (2) See input-output, real-time output. (4) To arrange items according to any specified set of rules. Synonymous output area with sort. An area of storage reserved for output. (5) (ISO) Deprecated term for instruction, sequence (1). output channel A channel for conveying data from a de¬ order-by-merging vice or logic element. (ISO) To order by repeated splitting and merging. output data (ISO) Data being delivered or to be order code delivered from a device or from a com¬ (ISO) Deprecated term for operation code. puter program.

ordering bias output device (ISO) The manner and degree by which (ISO) Synonym for output unit. the order of a set of items departs from

random distribution. An ordering bias output process will make the effort necessary to order a (ISO) The process that consists of the set of items more than or less than the delivery of data from a data processing effort that would be required for a similar system, from a subsystem, or from a de¬ set with random distribution. vice.

OR gate output program A gate that implements the logic OR op¬ (ISO) A utility program that organizes the erator. output process of a computer. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 111

output routine program, to load a segment of the (ISO) A utility routine that organizes the computer program in a storage area output process of a computer. hitherto occupied by parts of the com¬ puter program that are not currently output unit needed. (ISO) A device in a data processing sys¬ tem by which data may be received from the system. Synonymous with output overlay supervisor device. A routine that controls the proper sequencing and positioning of segments of overflow computer programs in limited storage dur¬ See arithmetic overflow. ing their execution.

overhead operation

(ISO) Synonym for housekeeping opera¬ overpunch tion. (1) To add holes in a card column that already contains holes. Overpunches overlay are often used to represent special (1) (ISO) In a computer program, a seg¬ characters. ment that is not permanently main¬ (2) To add holes to perforated tape to tained in internal storage. (2) The technique of repeatedly using the change a character, especially to same areas of internal storage during produce a delete character. different stages of a program. (3) Synonym for zone punch. (3) (ISO) In the execution of a computer 112 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

P page turning Synonym for paging.

pack paging (1) (ISO) To store data in a compact A time sharing technique in which pages form in a storage medium by taking are transferred between main storage and advantage of known characteristics of auxiliary storage. Synonymous with page the data and the storage medium, in turning. such a way that the original form of the data can be recovered, e.g., to panel make use of bit or byte locations that would otherwise go unused. See control panel, maintenance panel, op¬ (2) See disk pack. erator control panel.

packing density paper skip The number of useful storage cells per Synonym for paper throw. unit of dimension, e.g., the number of bits per inch stored on a magnetic tape track paper tape code or magnetic drum track. Synonym for perforated tape code.

padding paper throw (1) (ISO) A technique that incorporates The movement of paper through a printer fillers in data. at a speed greater than a single line spac¬ (2) (ISO) Deprecated term for filler. ing speed. Synonymous with paper skip.

page parallel A block of instructions, or data, or both, (1) Pertaining to the concurrent operation that can be located in main storage or in or simultaneous operation of two or auxiliary storage. Segmentation and load¬ more devices or to the concurrent per¬ ing of these blocks is automatically con¬ formance of two or more activities in trolled by a computer. a single device. (2) Pertaining to the concurrent or simul¬ page-at-a-time printer taneous occurrence of two or more Synonym for page printer. related activities in multiple devices or channels. page printer (3) Pertaining to the simultaneity of two (1) A device that prints one page at a or more processes. time, e.g., xerographic printer, cathode (4) Pertaining to the simultaneous process¬ ray tube printer, film printer. Synonymous with page-at-a-time print¬ ing of the individual parts of a whole, er. such as the bits of a character and (2) Contrast with character printer, line the characters of a word, using sepa¬ printer. rate facilities for the various parts. (5) Contrast with serial. page swapping Exchanging pages between main storage parallel adder and auxiliary storage. (ISO) A digital adder in which addition is AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 113

performed concurrently on digits in all the a combination of three out of twelve digit places of the operands. frequencies simultaneously transmitted over the channel. parallel addition (2) Contrast with serial transmission. (ISO) Addition that is performed concur¬

rently on digits in all the digit places of parameter the operands. (1) (ISO) A variable that is given a con¬ stant value for a specified application parallel computer and that may denote the application. (1) A computer having multiple arithmetic (2) See external program parameter, pre¬ or logic units that are used to accom¬ set parameter, program-generated plish parallel operations or parallel parameter. processing. (2) Contrast with serial computer. parameter word (ISO) A word that directly or indirectly parallel operation provides or designates one or more (1) The concurrent or simultaneous execu¬ parameters. tion of two or more operations in de¬ vices such as multiple arithmetic or logic units. parenthesis-free notation (2) Contrast with senal operation. (1) Any method of forming mathematical expressions in which expressions are parallel processing delimited by means other than paren¬ (1) The concurrent or simultaneous execu¬ theses, e.g., prefix notation, postfix no¬ tion of two or more processes in a tation. single unit. (2) Contrast with infix notation. (2) Contrast with serial processing.

parity bit parallel search storage A check bit appended to an array of bi¬ (1) A storage device in which one or nary digits to make the sum of all the bi¬ more parts of all storage locations are nary digits, including the check bit, always queried simultaneously. odd or always even. (2) Contrast with associative storage.

parity check parallel storage A check that tests whether the number of A storage device in which digits, charac¬ ones (or zeros) in an array of binary di¬ ters, or words, are accessed simultaneously gits is odd or even. Synonymous with or concurrently. odd-even check.

parallel transmission (1) In data communication, the simultane¬ partial carry ous transmission of a certain number (1) (ISO) In parallel addition, a proce¬ of signal elements constituting the dure in which some or all of the car¬ same telegraph or data signal. For ries are temporarily stored instead of example, use of a code according to being immediately transferred. which each signal is characterized by (2) Contrast with complete carry. 114 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

partition perforated-tape reader (ISO) Deprecated term for segment. A device that converts holes or cuts in perforated tape into coded electrical pulse pass patterns. (1) One cycle of processing a body of data. perforator (2) See sort pass. See receiving perforator.

patch peripheral control unit (1) A temporary electrical connection. Synonym for input-output controller. (2) (ISO) To make an improvised modifi¬ cation. To modify a routine in a peripheral equipment rough or expedient way. (ISO) In a data processing system, any equipment, distinct from the central proc¬ pattern recognition essing unit, that may provide the system (ISO) The identification of shapes, forms, with outside communication or additional or configurations by automatic means. facilities.

pattern sensitive fault peripheral transfer (1) A fault that appears in response to (ISO) The process of transmitting data some particular pattern of data. between two peripheral units. (2) Contrast with program sensitive fault. permanent storage pause Instruction (1) (ISO) A storage device whose content (1) (ISO) An instruction that specifies the cannot be modified. suspension of the execution of a com¬ (2) Synonymous with fixed storage. puter program. A pause instruction is (3) Contrast with erasable storage. usually not an exit. Synonymous with halt instruction. permutation (2) See optional pause instruction. (!)(ISO) An ordered arrangement of a given number of different elements PCM selected from a set. (1) Punched card machine. (2) Contrast with combination. (2) Pulse code modulation. phase PCS See assembly phase, compile phase, exe¬ Print contrast signal. cute phase, translate phase.

perforated tape picture A tape on which a pattern of holes or (ISO) In a programming language, a de¬ cuts is used to represent data. scription of a character string in which each position has associated with it a perforated tape code symbol representing the properties of the A code used to represent data on per¬ character that may occupy it, e.g., in CO¬ forated tape. Synonymous with paper BOL, 9999 is used as a picture of any tape code. 4-digit numeric word. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 115

pinboard polarized dipole magnetization (1) A perforated board into which pins Synonym for polarized return-to-zero are manually inserted to control the recording. operation of equipment. (2) Synonym for plugboard. polarized return-to-zero recording (RZ(P)) A method of retum-to-reference recording pitch in which zeros are represented by magnet¬ See feed pitch, row pitch, track pitch. ization in one sense, ones are represented by magnetization in the opposite sense, PL/I and the reference condition is the absence A programming language designed for use of magnetization. Synonymous with pola¬ in a wide range of commercial and scien¬ rized dipole magnetization. tific computer applications. Polish notation

plotter (ISO) Synonym for prefix notation. (ISO) An output unit that presents data in the form of a two-dimensional graph¬ polling ical representation. Interrogation of devices for purposes such as to avoid contention, to determine oper¬ plugboard ational status, or to determine readiness to (ISO) A perforated board into which send or receive data. plugs or pins may be placed to control the operation of equipment. Synonymous polyphase sort with control panel, pinboard. An unbalanced merge sort in which the distribution of sorted subsets is based on plugboard chart a Fibonacci series. A chart that shows, for a given job, where plugs or wires must be inserted position into a plugboard. Synonymous with plug¬ (1) (ISO) In a string, each location that ging chart. may be occupied by a character or bi¬ nary element and that may be identi¬ plugging chart fied by a serial number. Synonym for plugboard chart. (2) See bit position, punch position, sign position. pocket A card stacker in a sorter. positional notation (ISO) Synonym for positional representa¬

point tion system. See branchpoint, breakpoint, checkpoint, decimal point, entry point, radix point, positional representation reentry point, rerun point, restart point. (ISO) A representation of a real number in a positional representation system.

pointer An identifier that indicates the location of positional representation system an item of data. (ISO) Any numeration system in which a real number is represented by an ordered 116 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

set of characters in such a way that the (1) (ISO) A measure of the ability to dis¬ value contributed by a character depends tinguish between nearly equal values. upon its position as well as upon its va¬ (2) The degree of discrimination with lue. Synonymous with positional notation. which a quantity is stated. For exam¬ ple, a three-digit numeral discriminates positioning time among 1000 possibilities. (ISO) The time to mechanically position a (3) Contrast with accuracy. transducer relative to the location of the (4) See double-precision, multiple-preci¬ required data on a storage medium,e.g.,the time sion, single-precision, triple-precision. required to position a read-write head on a magnetic disk plus the time required for the data to arrive at the read-write head. predefined process In flowcharting, a process that is identi¬ fied only by name and that is defined el¬ sewhere. postfix notation (1) (ISO) A method of forming math¬ prefix notation ematical expressions in which each op¬ (1) (ISO) A method of forming math¬ erator is preceded by its operands and ematical expressions in which each op¬ indicates the operation to be per¬ erator precedes its operands and indi¬ formed on the operands or the inter¬ cates the operation to be performed mediate results that precede it. on the operands or the intermediate Synonymous with reverse Polish nota¬ results that follow it. Synonymous tion, suffix notation. with Lukasiewicz notation, Polish nota¬ (2) Contrast with infix notation, prefix no¬ tion. tation. (2) Contrast with infix notation, postfix (3) See also parentheses-free notation. notation. (3) See also parentheses-free notation. posting See event posting. preprocessor (ISO) A computer program that effects postmortem dump some preliminary computation or organiza¬ (ISO) Dumping that is performed at the tion. end of a run, usually for purposes of debugging, auditing, or documentation. pre-read head

postprocessor A read head placed relative to a second (ISO) A computer program that effects read head so that it may be used to read some final computation or organization. the data on a magnetic track before the data are read by the second read head.

pragmatics (ISO) The relationship of characters or preset groups of characters to their interpretation (ISO) To establish an initial condition, and use. such as the control values of a loop, or the value to which a parameter is to be precision bound. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 117

preset parameter measure of the contrast between a (ISO) A parameter that is bound when printed character and the paper on the computer program is constructed, which the character is printed. when it is flowcharted, coded, or com¬ (2) Contrast with print contrast ratio. piled.

print control character prestore A control character for print operations (1) (ISO) To store, before a computer such as line spacing, page ejection, or car¬ program, routine, or subroutine is en¬ riage return. tered, data that are required by the computer program, the routine, or the printed card form subroutine. The layout or format of the printed mat¬ (2) Contrast with initialize. ter on a card. The printed matter usually describes the purpose of the card and presumptive instruction (ISO) An instruction that is not an effec¬ designates the precise location of card tive instruction until it has been modified fields. in a prescribed manner. printer

prevarication See bar printer, chain printer, character (ISO) Synonym for irrelevance. printer, drum printer, matrix printer, on- the-fly printer, page printer. preventive maintenance (1) Maintenance specifically intended to print wheel prevent faults from occurring. Correc¬ A disk in a printing mechanism that pro¬ tive maintenance and preventive vides all characters of a font at a single maintenance are both performed dur¬ printing position. Synonymous with type ing maintenance time. wheel. (2) Contrast with corrective maintenance.

priority processing preventive maintenance time A method of operating a computer in Time, usually scheduled, used to perform which computer programs are processed in preventive maintenance. such a way that the order of operations to be performed is fully determined by a print contrast ratio system of priorities. (1) In optical character recognition, the ratio obtained by subtracting the re¬ privileged instruction flectance at an inspection area from (ISO) An instruction that may be used the maximum reflectance found within only by a supervisory program. a specified distance from that area, and dividing the result by that max¬ imum reflectance. problem description (2) Contrast with print contrast signal. (ISO) A statement of a problem, perhaps including a description of the method of

print contrast signal (PCS) solving it, the procedures and algorithms, (1) In optical character recognition, a etc. 118 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

problem-oriented language process control (ISO) A programming language that is Automatic control of a process, in which especially suitable for a given class of a computer is used for the regulation of problems. Procedure-oriented languages usually continuous operations or processes. such as FORTRAN, ALGOL; simulation languages such as GPSS, SIMSCRIPT; list processing processing languages such as LISP, IPL-V; See administrative data processing, information retrieval languages. automatic data processing, background processing, batch processing, business data problem time processing, data processing, electronic data In simulation, the duration of a process, processing, foreground processing, integrat¬ or the length of time between two speci¬ ed data processing, list processing, multi¬ fied events of a process. processing, parallel processing, priority processing, real-time processing, remote procedural language batch processing, sequential batch process¬ (ISO) Synonym for procedure-oriented ing, serial processing. language. processing system procedure See data processing system. (1) (ISO) The course of action taken for the solution of a problem. processing unit (2) The description of the course of action See central processing unit. taken for the solution of a problem. (3) See inline procedures. processor (1) In hardware, a data processor. procedure-oriented language (2) In software, a computer program that (ISO) A problem-oriented language that performs functions such as compiling, facilitates the expression of a procedure as assembling, and translating for a an explicit algorithm, e.g., FORTRAN, specific programming language. ALGOL, COBOL, PL/1. Synonymous (3) See central processor, data processor, with procedural language. language processor, multiprocessor.

process product (1) A course of events occurring according (ISO) The number or quantity that results to an intended purpose or effect. from a multiplication. (2) A systematic sequence of operations to produce a specified result. production time (3) To perform operations on data. That pan of operating time that is neither (4) See input process, output process, development time nor makeup time. predefined process. program processable scored card (1) (ISO) A schedule or plan that speci¬ A scored card including at least one sepa¬ fies actions that may or may not be rable pan that can be processed after taken. separation. (2) Loosely, a routine. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 119

(3) (ISO) To design, write, and test com¬ program loader puter programs. See initial program loader. (4) Loosely, to write a routine. (5) See assembly program, checking pro¬ programmed check gram, compiling program, computer (1) A check procedure that is a part of a program, control program, diagnostic computer program. program, editor program, executive (2) Contrast with automatic check. program, input program, library pro¬ gram, macrogenerating program, moni¬ programmed computer tor program, object program, output (ISO) Synonym for stored-program com¬ program, reenterable program, reloca¬ puter. table program, reusable program, self-

adapting program, self-organizing pro¬ programmer gram, snapshot program, sort program, A person who designs, writes, and tests source program, supervisory program, computer programs. target program, trace program, tran¬

slating program, utility program. programming (1) (ISO) The designing, writing, and test¬ program block ing of programs. In problem-oriented languages, a computer (2) See automatic programming, convex program subdivision that serves to group programming, dynamic programming, related statements, delimit routines, specify integer programming, linear program¬ storage allocation, delineate the applicabil¬ ming, macroprogramming, mathemati¬ ity of labels, or segment parts of the cal programming, minimum delay pro¬ computer program for other purposes. gramming, multiprogramming, nonlin¬ ear programming, quadratic program¬ program development time ming. That part of operating time that is used for debugging. programming flowchart (ISO) A flowchart representing the se¬ program execution time quence of operations in a computer pro¬ The interval during which the instructions gram. Synonymous with programming of an object program are executed. flow diagram.

program-generated parameter programming flow diagram (ISO) A parameter that is bound during (ISO) Synonym for programming flow¬ the execution of a computer program. chart. Synonymous with dynamic parameter. programming language program library (ISO) An artificial language established (1) (ISO) An organized collection of com¬ for expressing computer programs. puter programs that are sufficiently documented to allow them to be used programming module by persons other than their authors. A discrete identifiable set of instructions, (2) A collection of available computer usually handled as a unit, by an assem¬ programs and routines. bler, a compiler, or a linkage editor, a 120 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

loading routine, or other type of routine metic process but is effectively a random or subroutine. number sequence for the purpose for which it is required. programming system (ISO) One or more programming lan¬ pulse guages and the necessary software for us¬ (1) A variation in the value of a quantity, ing these languages with particular shon in relation to the time schedule automatic data processing equipment. of interest, the final value being the same as the initial value. program origin Synonymous with impulse. See computer program origin. (2) See clock pulse, synchronization pulse.

program parameter pulse repetition rate See external program parameter. The number of pulses per unit time.

program-sensitive fault pulse string (1) A fault that occurs as a result of Synonym for pulse train. some particular sequence of program steps. pulse train (2) Contrast with pattern-sensitive fault. A series of pulses having similar charac¬ teristics. Synonymous with pulse string. proper subset (ISO) Of a set, a subset that does not in¬ punch clude all the elements of the set. (1) A device for making holes in a data medium. protected location (2) A perforation, as in a punched card A storage location whose content is or paper tape. protected against accidental alteration, im¬ (3) See automatic-feed punch, card punch, proper alteration, or unauthorized access. calculating punch, digit punch, eleven punch, gang punch, hand-feed punch, protection keyboard punch, keypunch, numeric (1) An arrangement for restricting access punch, reproducing punch, spot punch, to or use of a system or pan of a system. summary punch, twelve punch, zone (2) See storage protection. punch.

pseudo code punch card A code that requires translation prior to (1) A card into which hole patterns can execution. be punched. (2) See Hollerith card. pseudo-instruction (ISO) Deprecated term for declaration. punch column (1) A line of punch positions parallel to pseudo-random number sequence the Y-datum line of a card. (ISO) An ordered set of numbers that has (2) , A line of punch positions along a been determined by some defined arith¬ card column. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 121

punched card x 2'2. Synonymous with binary numera¬ (1) A card punched with hole patterns. tion system. (2) See Hollerith card.

pushdown list punched card reader (ISO) A list that is constructed and main¬ Synonym for card reader. tained so that the next item to be re¬

punched tape trieved is the most recently stored item in Synonym for perforated tape. the list, i.e., last-in-first-out (LIFO). Sy¬ nonymous with stack. punching See interstage punching, multiple punch¬ pushdown storage ing. (ISO) A storage device that handles data in such a way that the next item to be punching position retrieved is the most recently stored item (ISO) Synonym for punch position. still in the storage device, i.e., last-in-first-

punching station out (LIFO). Synonymous with pushdown The place in a card track where a punch store. card is punched. pushdown store punch position (ISO) Synonym for pushdown storage. (ISO) A defined location on a card or tape where a hole may be punched to re¬ pushup list cord data. Synonymous with code posi¬ (ISO) A list that is constructed and main¬ tion, punching position. tained so that the next item to be re¬

punch row trieved is the earliest stored item still in A line of punch positions along a card the list, i.e., first-in-first-out (FIFO). row. pushup storage punctuation symbol (ISO) A storage device that handles data Synonym for delimiter. in such a way that the next item to be retrieved is the earliest stored item still in pure binary numeration system the storage device, i.e., first-in-first-out (ISO) The fixed-radix numeration system (FIFO). Synonymous with pushup store. that uses the binary digits and the radix 2, e.g., in this numeration system, the nu¬ meral 110.01 represents the number six pushup store and a quarter, i.e., 1 x 22 + 1 x 21 + 1 (ISO) Synonym for pushup storage. 122 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

quantum Q A subrange in quantization.

quadratic programming quarternary operator (1) (ISO) In operations research, a par¬ (ISO) An operator that requires exactly ticular case of nonlinear programming four operands. in which the function to be maximized or minimized is a quadratic function and the constraints are linear func¬ quarter squares mutiplier tions. An analog multiplier unit that uses the (2) Contrast with convex programming, identity xy=ki[(x+y)2-(x-y)2]. dynamic programming, integer pro¬ gramming, linear programming, math¬ quartet ematical programming, nonlinear pro¬ (ISO) A byte composed of four binary gramming. elements. Synonymous with four-bit byte.

quadruple-length register queue (ISO) Four registers that function as a See double-ended queue. single register. Each register may be in¬ dividually accessed. Synonymous with queued access method quadruple register. Any access method that synchronizes the transfer of data between the computer quadruple register program using the access method and (ISO) Synonym for quadruple-length regis¬ ter. input-output devices, thereby minimizing delays for input-output operations. qualified name (ISO) A data name explicitly accompanied quiescing by a specification of the class to which it The process of bringing a device or a sys¬ belongs in a specified classification system. tem to a halt by rejection of new requests for work. quantization The subdivision of the range of values of quinary a variable into a finite number of See biquinary code. nonoverlapping, but not necessarily equal, subranges or intervals each of which is quintet represented by an assigned value within (ISO) A byte composed of five binary the subrange. For example, a person’s elements. Synonymous with five-bit byte. age is quantized for most purposes with a quantum of one year. quotient

quantize (1) (ISO) The number or quantity that is (ISO) To divide the range of a variable the value of the dividend divided by into a finite number of non-overlapping the value of the divisor and that is intervals, that are not necessarily equal, one of the results of a division opera¬ and to designate each interval by an as¬ tion. signed value within that interval. (2) Contrast with remainder. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 123

R radix numeration system (ISO) A positional representation system in which the ratio of the weight of any radial transfer one digit place to the weight of the digit (1) (ISO) The process of transmitting data place with the next lower weight is a between a peripheral unit and a unit positive integer. The permissible values of of equipment that is more central the character in any digit place range than that peripheral unit. Synony¬ from zero to one less than the radix of mous with input-output (1). that digit place. Synonymous with radix (2) Synonymous with input process (2), notation. output process.

radix point radix (ISO) In a representation of a number ex¬ (1) (ISO) Of a digit place in a radix nu¬ pressed in a radix numeration system, the meration system, the postive integer location of the separation of the charac¬ by which the weight of the digit place ters associated with the integral part from is multiplied to obtain the weight of those associated with the fractional part. the digit place with the next higher

weight, e.g., in the decimal numeration random access system the radix of each digit place is (1) In COBOL, an access mode in which 10, in a biquinary code the radix of specific logical records are obtained each fives position is 2. from or placed into a mass storage (2) (ISO) Deprecated term for base. file in a nonsequential manner. (3) See mixed-radix numeration system. (2) (ISO) Synonym for direct access.

radix complement random access storage (1) (ISO) A complement obtained by sub¬ (ISO) Synonym for direct access storage. tracting each digit of the given num¬

ber from the number that is one less random number than the radix of that digit place, (1) (ISO) A number selected from a then adding one to the least signifi¬ known set of numbers in such a man¬ cant digit of the result and executing ner that the probability of occurrence any carries required, e.g., 830 is the of each number in the set is predeter¬ tens complement, i.e., the radix com¬ mined. plement of 170 in the decimal numer¬ (2) A number obtained by chance. ation system using three digits. (3) One of a sequence of numbers consid¬ Synonymous with noughts complement. ered appropriate for satisfying certain (2) See dimished radix complement. statistical tests or believed to be free from conditions which might bias the radix-minus-one complement result of a calculation. (ISO) Synonym for diminished radix com¬

plement. random number sequence (1) (ISO) An ordered set of numbers radix notation each of which may not be predicted (ISO) Synonym for radix numeration sys¬ only from a knowledge of its tem. predecessors. 124 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(2) See also pseudo-random number se¬ consulted before spillover of electrons quence. causes a loss of data stored in surround¬ ing spots. The surrounding data must be random-walk method restored before the deterioration results in In operations research, a variance-reducing any loss of data. method of problem analysis in which ex¬ perimentation with probabilistic variables read cycle time is traced to determine results of a signifi¬ (ISO) The minimum time interval between cant nature. the starts of successive read cycles of a device that has separate reading and writ¬ range ing cycles. (1) (ISO) The set of values that a quanti¬

ty or function may take. reader (2) The difference between the highest (1) In micrographics, a device that en¬ and lowest value that a quantity or larges microimages for viewing. function may assume. (2) See card reader, character reader, (3) (ISO) Deprecated term for span. perforated-tape reader. (4) See error range.

reader-printer rank In micrographics, a device that performs (ISO) Synonym for level number. the functions of a reader and a printer to produce hard copy enlargements of select¬ rate ed microimages. See average information rate, average transinformation rate, data signalling rate, read head pulse repetition rate. A magnetic head that only reads,

ratio reading See error ratio, print contrast ratio, read- (ISO) The acquisition or interpretation of around ratio. data from a storage device, from a data medium, or from another source. rational number (ISO) A real number that is the quotient of an integer divided by an integer other reading station than zero. Synonym for read station.

read read-only memory (ROM) (1) (ISO) To acquire or to interpret data (ISO) Synonym for fixed storage. from a storage device, from a data medium, or from another source. read-only storage (2) See destructive read, nondestructive (ISO) Synonym for fixed storage, perma¬ read. nent storage.

read-around ratio read-out device The number of times a specific spot, digit, (ISO) Synonym for character display de¬ or location in electrostatic storage may be vice. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 125 I read station (ISO) Synonym for real-time processing (ISO) The place in a card path where the (1). data on a punched card are read. Synonymous with reading station, sensing real-time output station. (ISO) Output data delivered from a data processing system within time limits that read/write head are determined by the requirements of (ISO) Synonym for magnetic head. some other system or at instants that are so determined.

real address The address of an actual storage location real-time processing in real storage. (1) (ISO) A mode of operation of a data processing system when performing real-time jobs. Synonymous with real number real-time operation. (ISO) A number that may be represented (2) (ISO) The manipulation of data that by a finite or infinite numeral in a fixed- are required or generated by some radix numeration system. process while the process is in opera¬ tion; usually the results are used to real storage influence the process, and perhaps The execution space in a virtual storage related processes, while it is occurring. system that is directly controlled by a cen¬ tral processing unit. real-time simulation The operation of a simulator such that real time the time scale factor is equal to one for a (1) Pertaining to the actual time during physical time specified by the system be¬ which a physical process transpires. ing simulated and by the corresponding (2) Pertaining to the performance of a computer time of the simulator. computation during the actual time that the related physical process tran¬ real-time working spires, in order that results of the (ISO) Deprecated term for real-time proc¬ computation can be used in guiding essing. the physical process.

receiving perforator real-time control A punch that converts coded electrical (ISO) The control of a process by real¬ pulse patterns into hole patterns or cuts in time processing. perforated tape. Synonymous with tape punch. real-time input (ISO) Input data received into a data recognition processing system within time limits that See character recognition, magnetic ink are determined by the requirements of character recognition, optical character some other system or at instants that are recognition, pattern recognition. I so determined. record real-time operation (1) (ISO) A collection of related data or 126 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

words treated as a unit, e.g., in stock numbers by substitution formulae in which control, each invoice could constitute the function is an operand. one record. (2) See logical record, variable-length re¬ recursively defined sequence cord. (ISO) A series of terms in which each term after the first is determined by an record gap operation in which the operands are some (ISO) Deprecated term for interblock gap. or all of the preceding terms.

recording See double-pulse recording, electron-beam recursive routine recording, magnetic recording, non-pola- (ISO) A routine that may be used as a rized retum-to-zero recording, non-retum- routine of itself, calling itself directly or to-change recording, non-return-to-reference being called by another routine, one that recording, non-retum-to-zero change-on- it itself has called. The use of a recursive ones recording, non-retum-to-zero (change) routine or computer program usually re¬ recording, non-retum-to-zero recording, quires the keeping of records of the status polarized return-to-zero recording, retum- of its unfinished uses in, for example, a to-reference recording. pushdown list.

recording area (ISO) Synonym for film frame. recursive subroutine (ISO) A subroutine that may be used as recording density a subroutine of itself, calling itself directly The number of bits in a single linear or being called by another subroutine, one track measured per unit of length of the that it itself has called. The use of a recording medium. recursive subroutine or computer program usually requires the keeping of records of record layout the status of its unfinished uses in, for ex¬ (ISO) The arrangement and structure of ample, a pushdown list. data or words in a record including the order and size of the components of the record. reduction (1) (ISO) In micrographics, a measure of record length the number of times the linear dimen¬ (ISO) The number of words or characters sions of an object are reduced when forming a record. photographed, expressed as 16x, 24x, etc. record separator character (RS) (2) See data reduction. (ISO) The information separator intended to identify a logical boundary between re¬ cords. redundancy (1) (ISO) In information theory, the

recursive function amount R by which the decision con¬ (ISO) A function whose values are natural tent Ho exceeds the entropy H; in numbers that are derived from natural mathematical notation. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 127

simultaneously. Synonymous with reenter¬ able program. R=H0-H reentrant routine (ISO) A routine that may be entered repeatedly and may be entered before pri¬ Usually, messages can be represented or executions of the same routine have with fewer characters by using suitable been completed, subject to the require¬ codes; the redundancy may be consid¬ ment that neither its external program ered as a measure of the decrease of parameters nor any instructions are modi¬ length of the messages thus achieved. fied during its execution. A reentrant (2) See relative redundancy. routine may be used by more than one computer program simutaneously. redundancy check bit Synonymous with reenterable routine. A check bit that is derived from a charac¬ ter and appended to the character. reentrant subroutine (ISO) A subroutine that may be entered redundancy check character repeatedly and may be entered before pri¬ (1) A check character that is derived from or executions of the same subroutine have a record and appended to the record. been completed, subject to the require¬ (2) See cyclic redundancy check character. ment that neither its external program parameters nor any instructions are modi¬ reel fied during its execution. A reentrant (ISO) A cylinder with flanges on which subroutine may be used by more than tape or film may be wound. one computer program simultaneously. Synonymous with reenterable subroutine. reenterable program (ISO) Synonym for reentrant program. reentry point (ISO) The address or the label of the in¬ reenterable routine struction at which the computer program (ISO) Synonym for reentrant routine. that called a subroutine is reentered from the subroutine. reenterable subroutine (ISO) Synonym for reentrant subroutine. reference edge (1) (ISO) That edge of a data medium reentrant program used to establish specifications or (ISO) A computer program that may be measurements in or on the data medi¬ entered repeatedly and may be entered um. Synonymous with guide edge. before prior executions of the same com¬ (2) See document reference edge. puter program have been completed, sub¬ ject to the requirement that neither its ex¬ reflected binary code ternal program parameters nor any in¬ Synonym for gray code. structions are modified during its execu¬ tion. A reentrant program may be used regeneration by more than one computer program See signal regeneration. 128 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

regenerative track relative redundancy Part of a track on a magnetic drum or (ISO) In information theory, the ratio r of magnetic disk used in conjunction with a the redundancy R to the decision content H ; in mathematical notation: read head and a write head that are con¬ O’ nected to function as a circulating storage. Synonymous with revolver track.

register r -1 - H°~H " ~ H0 " Ho (1) (ISO) In a computer, a storage de¬ vice, usually intended for some special purpose, capable of storing a specified amount of data such as a bit or a reliability word. (ISO) The ability of a funtional device to (2) See address register, base address reg¬ perform its intended function under stated ister, base register, circulating register, conditions for a stated period of time. clock register, double-length register, floating-point register, general-purpose relocatable address register, index register, instruction ad¬ (ISO) An address that is adjusted when dress register, instruction register, n- the computer program containing it is tuple-length register, quadruple-length relocated. register, return code register, sequence control register, shift register, time reg¬ relocatable program ister, triple-length register. (ISO) A computer program that is in such a form that it may be relocated. registration The accurate positioning of an entity rela¬ relocate tive to a reference. (ISO) To move a computer program or part of a computer program, and to ad¬ relative address just the necessary address references so (ISO) An address expressed as a differ¬ that the computer program can be execut¬ ence with respect to a base address. ed after being moved.

relative addressing relocating loader (ISO) A method of addressing in which A loader that adjusts addresses, relative to the address part of an instruction contains the assembled origin, by the relocation a relative address. factor.

relative coding relocation Coding that uses machine instructions with See dynamic relocation. relative addresses. relocation dictionary relative error The part of an object module or load (ISO) The ratio of an absolute error to module that identifies all addresses that the true, specified, or theoretically correct must be adjusted when a relocation oc¬ value of the quantity that is in error. curs. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 129

relocation factor cond level subset. A selection sort is The algebraic difference between the as¬ applied to this second level subset, the sembled origin and the loaded origin of a selected item in this second level sub¬ computer program. set is appended to the sorted set and is replaced by the next eligible item remainder in the original subset, and the process (1) (ISO) In a division operation, the repeated until all items are in the number or quantity that is the undi¬ sorted set. vided part of the dividend, having an (2) See also tournament sort. absolute value less than the absolute

value of the divisor, and that is one reperforator of the results of a division operation. Receiving perforator. (2) Contrast with quotient.

repertoire remote access See instruction repertoire. Pertaining to communication with a data processing facility through a data link. repetition instruction An instruction that causes one or more in¬ remote batch entry structions to be executed an indicated (ISO) Submission of batches of jobs number of times. through an input-output unit that has ac¬ cess to a computer through a data link. repetitive addressing (ISO) A method of implied addressing, remote batch processing applicable only to zero-address instruc¬ (ISO) Batch processing in which input- tions, in which the operation part of an output units have access to a computer instruction implicitly addresses the ope¬ through a data link. rands of the last instruction executed.

remote job entry (RJE) representation (ISO) Submission of jobs through an in¬ See analog representation, coded represen¬ put unit that has access to a computer tation, digital representation, discrete re¬ through a data link. presentation, floating-point representation, incremental representation, linear represen¬ remote station tation, number representation, numeric re¬ Data terminal equipment for communicat¬ ing with a data processing system through presentation, variable-point representation. a data link. representation system

re-order See fixed-point representation system, (ISO) Deprecated term for order (1). floating-point representation system, num¬ ber representation system, positional re¬

repeated selection sort presentation system, variable-point re¬ (1) A selection sort in which the set of presentation system. items is divided into subsets and one item, that fits specified criteria, from reproduce each subset is selected to form a se¬ Synonym for duplicate. 130 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

reproducer prescribed initial state, not necessarily (ISO) Synonym for reproducing punch. that denoting zero. (3) Contrast with set. reproducing punch (ISO) A punched card device that residual error ratio prepares one punched card from another The error ratio remaining after attempts punched card copying all or part of the at correction. data from the punched card that is read. Synonymous with reproducer. residue check A validation check in which an operand is

rerun divided by a number n to generate a (1) (ISO) A repeat of a machine run remainder that is then used for checking. Synonymous with modulo-n check. from its beginning, usually made desirable or necessary by a false start, by an interruption, or by a change. resolver A device whose input is a vector quantity (2) (ISO) To perform a rerun. and whose outputs are components of the vector. rerun point That location, in the sequence of instruc¬ response tions in a computer program, at which all See spectral response. information pertinent to the rerunning of the program is available. response duration (ISO) The time duration between the start rescue point of a pulse which influences a storage cell (ISO) Synonym for restart point. and the end of the resulting response of that storage cell. reserved word (ISO) A word of a source language response time whose meaning is fixed by the particular (ISO) The elapsed time between the end rules of that language and cannot be al¬ of an enquiry or demand on a data proc¬ tered for the convenience of any one com¬ essing system and the beginning of the re¬ puter program expressed in the source sponse, e.g., the length of time between language; computer programs expressed in the end of an enquiry and the display of the source language may also be prohibit¬ the first character of the response at a us¬ ed from using such words in other con¬ er terminal. texts in the computer program. For ex¬

ample, SINE may be a reserved word to restart call a subroutine for computing the sine (1) (ISO) The resumption of the execution function; in COBOL, the COBOL words. of a computer program using the data recorded at a checkpoint. reset (2) (ISO) To perform a restart. (1) (ISO) To cause a counter to take the state corresponding to a specified ini¬ restart condition tial number. (ISO) In the execution of a computer pro¬ (2) (ISO) To restore a storage device to a gram, a condition that can be re-estab- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 131

lished and that permits a restart of the return-to-reference recording computer program. (ISO) The magnetic recording of binary characters in which the pattern of magnet¬ restart instruction ization used to represent zeros and ones (ISO) An instruction in a computer pro¬ occupies only part of the storage cell, the gram at which the computer program may remainder of the cell being magnetized to be restarted. a reference condition.

restart point reusable program (1) (ISO) A place in a computer program (ISO) A computer program that may be at which its execution may be loaded once and executed repeatedly, sub¬ restarted; in particular, the address of ject to the requirements that any instruc¬ a restart instruction. Synonymous with tions that are modified during its execu¬ rescue point. tion are returned to their initial states and (2) (ISO) Deprecated term for restart con¬ that its external program parameters are dition. preserved unchanged.

result reusable routine (ISO) An entity produced by the perfor¬ (ISO) A routine that may be loaded once mance of an operation. and executed repeatedly, subject to the requirements that any instructions that are retrieval modified during its execution are returned See information retrieval. to their initial states and that its external program parameters are preserved un¬ retrieval code changed. In micrographics, a code used for manual or automatic retrieval of microimages. reverse direction flow In flowcharting, a flow in a direction oth¬ return er than left to right or top to bottom. (1) (ISO) Within a subroutine, to bind a variable in the computer program that reverse Polish notation called the subroutine. (ISO) Synonym for postfix notation. (2) (ISO) Within a subroutine, to effect a link to the computer program that called the subroutine. reversible counter (3) See carriage return. (ISO) A device whose state represents a number and that, on receipt of an appro¬

return character priate signal, causes the number represent¬ See carriage return character. ed to be increased or decreased by unity or by an arbitrary constant; the device is

return code usually capable of bringing the number A code used to influence the execution of represented to a specific value, such as succeeding instructions. zero.

return code register revolver track A register used to store a return code. Synonym for regenerative track. 132 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

right-justify rounding are rounding down, rounding (1) (ISO) To shift the contents of a up, and rounding off. register, if necessary, so that the (2) Contrast with truncation. character at the right-hand end of the data that have been read or loaded round down into the register is at a specified posi¬ (ISO) To round, making no adjustment to tion in the register. the part of the numeral that is retained. (2) (ISO) To control the positions of If a numeral is rounded down, its abso¬ characters on a page so that the lute value is not increased. Rounding right-hand margin of the printing is down is a form of truncation. regular.

(3) To align characters horizontally so rounding error that the right-most character of a (ISO) An error due to rounding. string is in a specified position.

round off RJE (1) (ISO) To round, adjusting the part of (ISO) Remote job entry the numeral that is retained by adding 1 to the least significant of its digits, rollback and executing any necessary carries if A programmed return to a prior check¬ and only if the most significant of the point. digits deleted was equal to or greater than half the radix of its digit place. roll-in (2) (ISO) To round, adjusting the part of To restore in main storage, data or one the numeral retained by adding 1 to or more computer programs that were the least significant of its digits, and previously rolled out. executing any necessary carries, if (a) the most significant of the digits delet¬ roll-out ed was greater than half the radix of To transfer data or one or more computer that digit place, or (b) the most sig¬ programs from main storage to auxiliary nificant of the digits deleted was storage for the purpose of freeing main equal to half the radix and one or storage for another use. more of the following digits were greater than zero, or (c) the most sig¬ ROM nificant of the digits deleted was (ISO) Read-only memory. equal to half the radix, all the follow¬ ing digits were equal to zero, and the

round least significant of the digits retained (1) (ISO) To delete or omit one or more was odd. In (c), even may be sub¬ of the least significant digits in a posi¬ stituted for odd. tional representation and to adjust the part retained in accordance with some round up specified rule. The purpose of round¬ (ISO) To round, adjusting the part of the ing is usually to limit the precision of numeral that is retained by adding 1 to the numeral or to reduce the number the least significant of its digits, and ex¬ of characters in the numeral, or to do ecuting any necessary carries if and only both. The most common forms of if one or more non-zero digits have been AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 133

deleted. If a numeral is rounded up, its of adjacent rows measured along a track. absolute value is not decreased. Synonymous with array pitch.

routine RPG (1) (ISO) An ordered set of instructions Report program generator. that may have some general or fre¬ quent use. RS (2) See dump routine, input routine, li¬ The record separator character. brary routine, output routine, recursive routine, reentrant routine, reusable routine, subroutine, supervisory routine, run tracing routine, utility routine. (1) (ISO) A single performance of one or

more jobs. row (2) A single, continuous peformance of a (1) A horizontal arrangement of characters computer program or routine. or other expressions. (2) Contrast with column. run duration (3) See card row, mark-sense row, punch row. (ISO) Synonym for runmng time.

row binary running time (1) Pertaining to the binary representation (ISO) The elapsed time taken for the exe¬ of data on cards in which the signifi¬ cution of a computer program.

cances of punch positions are assigned Synonymous with run duration. along card rows. For example, each row in an 80-column card may be RZ(NP) used to represent 80 consecutive bi¬ (ISO) Non-polarized return-to-zero record¬ nary digits. (2) Contrast with column binary. ing.

row pitch RZ(P) The distance between corresponding points (ISO) Polarized return-to-zero recording. 134 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

s pattern recognition, or character recog¬ nition. (2) See flying spot scanner, optical scan¬ sample ner. (ISO) To obtain the values of a function for regularly or irregularly spaced distinct scheduled maintenance values of an independent variable. (ISO) Maintenance carried out in accord¬ ance with an established schedule. sampling (1) Obtaining the values of a function for scheduler regularly or irregularly spaced distinct A computer program designed to perform values of an independent variable. functions such as scheduling, initiation, (2) In statistics, obtaining a sample from and termination of jobs. a population.

scored card save area (It) A special card that contains one or An area of main storage in which the more scored lines to facilitate precise contents of registers are saved. folding or separation of certain parts of the card. scalar (2) See processable scored card. (1) (ISO) A quantity characterized by a single number. search (2) Contrast with vector. (1) (ISO) The examination of a set of items for one or more having a given scale property. (1) (ISO) To change the representation of (2) (ISO) To examine a set of items for a quantity, expressing it in other units, one or more having a given property. so that its range is brought within a (3) See binary search, chaining search, di¬ specified range. chotomizing search, Fibonacci search. (2) To adjust the representation of a quantity by a factor in order to bring its range within prescribed limits. search cycle (ISO) The part of a search that is repeat¬

scale factor ed for each item, normally consisting of (1) (ISO) A number used as a multiplier locating the item and carrying out a com¬ in scaling. parison. (2) See time scale factor. search key scan (ISO) In the conduct of a search, the To examine sequentially, part by part. data to be compared to specified parts of each item. scanner (1) (ISO) A device that examines a spa¬ section tial pattern one part after another, (ISO) Deprecated term for segment. and generates analog or digital signals corresponding to the pattern. Scan¬ sector ners are often used in mark sensing, (ISO) A part of a track or band on a AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 135

magnetic drum, a magnetic disk, or a self-checking code disk pack. Synonym for error detecting code.

seek self-organizing computer (1) To selectively position the access (ISO) A computer that has the ability to mechanism of a direct access device. make rearrangements in its internal struc¬ (2) (ISO) Deprecated term for search, ture. search cycle. self-organizing program segment (ISO) A computer program that has the (1) (ISO) A self-contained portion of a ability to make rearrangements in its in¬ computer program that may be ex¬ ternal structure. ecuted without the entire computer program necessarily being maintained self-relative address in internal storage at any one time. (ISO) A relative address that uses as base (2) (ISO) To divide a computer program address the address of the instruction in into segments. which it appears.

selection check self-relative addressing A check that verifies the choice of de¬ (ISO) A method of addressing in which vices, such as registers, in the execution of the address part of an instruction contains an instruction. a self-relative address.

selection sort semantics (1) A sort in which the items in a set are (1) (ISO) The relationships of characters examined to find an item that fits or groups of characters to their mean¬ specified criteria; this item is append¬ ings, independent of the manner of ed to the sorted set and removed their interpretation and use. from further consideration, and the (2) The relationships between symbols and process repeated until all items are in their meanings. the sorted set. (2) See repeated selection sort. sensing See mark sensing. selective dump (ISO) The dumping of the contents of sensing station one or more specified storage areas. (ISO) Synonym for read station.

self-adapting computer sentinel (ISO) A computer that has the ability to Synonym for flag. change its performance characteristics in response to its environment. separating character (ISO) Synonym for information separator. self-adapting program (ISO) A computer program that has the separator ability to change its performance charac¬ (1) Synonym for delimiter. teristics in response to its environment. (2) See information separator. 136 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(3) See also file separator character, group sequential circuit separator character, record separator A logic device whose output values, at a character, unit separator character. given instant, depend upon its input va¬ lues and internal state at that instant, and septet whose internal state depends upon the im¬ (ISO) A byte composed of seven binary mediately preceding input values and the elements. Synonymous with seven-bit preceding internal state. A sequential cir¬ byte. cuit can assume a finite number of inter¬ nal states and may therefore be regarded sequence as a finite automaton. (1) (ISO) A series of items that have

been sequenced. sequential computer (2) An arrangement of items according to A computer in which events occur in time a specified set of rules, e.g., items ar¬ sequence, with little or no simultaneity or ranged alphabetically, numerically, or overlap of events. chronologically. (3) (ISO) Deprecated term for order. sequential control (4) (ISO) Synonym for collating sequence. (ISO) A mode of computer operation in (5) See calling sequence, collating se¬ which instructions are executed in an im¬ quence, pseudo-random number se¬ plicitly defined sequence until a different quence, random number sequence, sequence is explicitly initiated by a jump recursively defined sequence. instruction. (6) Contrast with order.

sequential logic element sequence-by-merging (1) A device having at least one output (ISO) To sequence by repeated splitting channel and one or more input chan¬ and merging. nels, all characterized by discrete states, such that the state of each out¬ sequence control register put channel is determined by the (ISO) Synonym for instruction address previous states of the input channels. register. (2) Contrast with combinational logic ele¬ ment. sequencing key Synonym for sort key. sequential operation

sequential (ISO) A mode of operation in which two (1) Pertaining to the occurrence of events or more operations are performed one aft¬ in time sequence, with no simultaneity er another. Synonymous with consecutive or overlap of events. operation. (2) Contrast with consecutive. (3) See also concurrent, simultaneous. serial (1) (ISO) Pertaining to the sequential per¬

sequential batch processing formance of two or more activities in A mode of operating a computer in which a single device. In English, the a run must be completed before another modifiers serial and parallel usually run can be started. refer to devices, as opposed to se- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 137

quential and consecutive, which refer that manipulates all bits of a word to processes. serially. (2) Pertaining to the sequential or con¬ (3) Contrast with parallel computer. secutive occurrence of two or more related activities in a single device or serializer channel. (ISO) A device that converts a space dis¬ (3) Pertaining to the sequential processing tribution of simultaneous states represent¬ of the individual parts of a whole, ing data into a corresponding time se¬ such as the bits of a character or the quence of states. Synonymous with characters of a word, using the same dynamicizer. facilities for successive parts. (4) Contrast with parallel. serial number (ISO) An integer denoting the position of serial access an item in a senes. (1) (ISO) The facility to obtain data from a storage device or to enter data into serial operation a storage device in such a way that (1) Pertaining to the sequential con¬ the process depends on the location of secutive execution of two or more op¬ that data and on a reference to data erations in a single device such as an previously accessed. arithmetic or logic unit. (2) Pertaining to the sequential or con¬ (2) (ISO) Deprecated term for sequential secutive transmission of data to or operations. from storage. (3) Contrast with parallel operation. (3) Contrast with direct access.

serial processing serial access storage (1) Pertaining to the sequential or con¬ (ISO) A storage in which the access time secutive execution of two or more is dependent upon the location of the processes in a single device such as a data. channel or processing unit. (2) Contrast with parallel processing. serial adder (ISO) A digital adder in which addition is performed by adding, digit place after di¬ serial sort git place, the corresponding digits of the A sort that requires only sequential access operands. to the items in a set. A serial son can be performed using only serial access stor¬

serial addition age devices. (ISO) Addition that is performed by add¬ ing, digit place after digit place, the corre¬ serial transmission sponding digits of the operands. (1) In data communication, transmission at successive intervals of signal ele¬

serial computer ments constituting the same telegraph (1) A computer having a single arithmetic or data signal. The sequential ele¬ and logic unit. ments may be transmitted with or (2) A computer some specified characteris¬ without interruption, provided that tic of which is serial, e.g., a computer they are not transmitted simultaneous- 138 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

ly. For example, telegraph transmis¬ (2) An arrangement of data or devices to sion by a time divided channel. solve a particular problem. (2) Contrast with parallel transmission. setup diagram

service program (ISO) A diagram specifying a given com¬ (ISO) Synonym for utility program. puter setup.

service routine seven-bit byte (ISO) Synonym for utility routine. (ISO) Synonym for septet.

servomechanism sexadecimal (1) An automatic device that uses feed¬ (1) (ISO) Pertaining to a selection, choice, back to govern the physical position or condition that has sixteen possible of an element. different values or states. (2) A feedback control system in which at (2) (ISO) Pertaining to a fixed-radix nu¬ least one of the system signals repre¬ meration system having a radix of six¬ sents mechanical motion. teen. Synonymous with hexadecimal.

set sextet (1) (ISO) A finite or infinite number of (ISO) A byte composed of six binary ele¬ objects of any kind, of entities, or of ments. Synonymous with six-bit byte. concepts, that have a given property or properties in common. Shannon (2) (ISO) To cause a counter to take the (ISO) In information theory, a unit of state corresponding to a specified logarithmic measures of information equal number. Contrast with reset (1). to the decision content of a set of two (3) (ISO) To place a storage device into mutually exclusive events expressed by the a specified state, usually other than logarithm to base two, e.g., the decision that denoting zero. Contrast with re¬ content of a character set of eight charac¬ set (2). ters equals three Shannons. Synonymous (4) See alphabetic character set, alphabetic with information content binary unit. coded character set, alphanumeric character set, alphanumeric coded Sheffer stroke character set, card set, character set, Synonym for NAND. coded character set, code set, empty set, instruction set, machine instruction shift set, numeric character set, numeric (1) (ISO) The concerted movement of coded character set, universal set. some or all of the characters of a word each by the same number of setup character places in the direction of a (1) (ISO) In a computer which consists of specified end of the word. an assembly of individual computing (2) See arithmetic shift, end-around shift, units, the arrangement of interconnec¬ logical shift. tions between the units, and the ad¬ justments needed for the computer to shift-in character (SI) operate upon a given problem. (ISO) A code extension character, used to AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 139

terminate a sequence that has been intro¬ signal distance. duced by the shift-out character, that The number of digit positions in which makes effective the graphic characters of the corresponding digits of two binary the standard character set. words of the same length are different. Synonymous with hamming distance.

shift-out character (SO) (ISO) A code extension character that signal regeneration substitutes for the graphic characters of (ISO) Signal transformation that restores a the standard character set an alternative signal so that it conforms to its original specification. set of graphic characters upon which agreement has been reached or that has signal shaping been designated using code extension (ISO) Synonym for signal transformation. procedures.

signal transformation shift register (ISO) The action of modifying one or (ISO) A register in which shifts are per¬ more characteristics of a signal, such as its formed. maximum shape or timing. Synonymous with signal shaping. short card A special-purpose paper card that is short¬ sign bit er in length than a general purpose paper (ISO) A bit or a binary element that oc¬ card; e.g., a 51-column card. cupies a sign position and indicates the algebraic sign of the number represented SI by the numeral with which it is associat¬ The shift-in character. ed.

sifting sort sign character Synonym for bubble sort. (ISO) A character that occupies a sign position and indicates the algebraic sign sight check of the number represented by the numeral A check performed by sighting through with which it is associated. the holes of two or more aligned punched

cards toward a source of light to verify sign digit the punching, e.g., to determine if a hole (ISO) A digit that occupies a sign position has been punched in a corresponding and indicates the algebraic sign of the punch position on all cards in a card number represented by the numeral with deck. which it is associated.

signal significance (1) (ISO) A time-dependent value at¬ (ISO) Synonym for weight. tached to a physical phenomenon and conveying data. significant digit (2) See inhibiting signal, start signal, stop (ISO) In a numeral, a digit that is need¬ signal. ed for a given purpose; in particular, a 140 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

digit that must be kept to preserve a giv¬ operations performed by a computer en accuracy or a given precision. or the representation of operations of a computer by those of another com¬ significant digit arithmetic puter. (ISO) A method of making calculations (2) See real-time simulation. using a modified form of a floating-point

representation system in which the number simulator of significant digits in the result is deter¬ (1) (ISO) A device, data processing sys¬ mined with reference to the number of tem, or computer program that repre¬ significant digits in the operands, the op¬ sents certain features of the behavior eration performed, and the degree of of a physical or abstract system. precision available. (2) See computer simulator.

significant figure simultaneous (ISO) Deprecated term for significant di¬ (1) (ISO) Pertaining to the occurrence of git. two or more events at the same in¬ stant of time. sign position (2) Contrast with concurrent. (ISO) A position, normally located at one (3) See also consecutive, sequential. end of a numeral, that contains an indica¬ tor denoting the algebraic sign of the number represented by the numeral. simultaneous computer (ISO) A computer that contains a separate simulate unit to perform each portion of the entire (1) (ISO) To represent certain features of computation concurrently, the units being the behavior of a physical or abstract interconnected in a way determined by system by the behavior of another the computation; at different times in a system, e.g., to represent a physical run, a given interconnection carries signals phenomenon by means of operations representing different values of the same performed by a computer or to repre¬ variable, e.g., a differential analyzer. sent the operations of a computer by those of another computer. simultaneous operation (2) To imitate one system with another, (ISO) A mode of operation in which two primarily by software, so that the or more events occur at the same instant imitating system accepts the same of time. data, executes the same computer pro¬ grams, and achieves the same results single-address as the imitated system. Pertaining to an instruction format con¬ (3) Contrast with emulate. taining one address part. Synonymous simulation with one-address. (1) (ISO) The representation of certain features of the behavior of a physical single precision or abstract system by the behavior of (ISO) Pertaining to the use of one com¬ another system, e.g., the representation puter word to represent a number in ac¬ of physical phenomena by means of cordance with the required precision. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 141

single step tents of one or more specified storage Pertaining to a method of operating a areas. computer in which each step is performed (2) A selective dump performed at various in response to a single manual operation. points in a machine run.

single-step operation snapshot program (ISO) A mode of operating a computer in (ISO) A trace program that produces out¬ which a single computer instruction or put data only for selected instructions or part of a computer instruction is executed for selected conditions. in response to an external signal. Synonymous with step-by-step operation. SO The shift-out character. sink See data sink, message sink. software (1) (ISO) Computer programs, procedures, six-bit byte rules, and possibly associated (ISO) Synonym for sextet. documentation concerned with the op¬ eration of a data processing system. skeletal code (2) Contrast with hardware. (ISO) A set of instructions in which some parts such as addresses must be completed SOH or specified in detail each time the set is (ISO) The start-of-heading character. used.

solid state component skew A component whose operation depends on The angular displacement of a symbol or the control of electric or magnetic data medium from the intended or ideal phenomena in solids, e.g., a transistor, placement. crystal diode, ferrite core.

skip sonic delay line (1) To ignore one or more instructions in Synonym for acoustic delay line. a sequence of instructions.

(2) To pass over one or more positions sort on a data medium, e.g., to perform (1) The operation of sorting. one or more line feed operations. (2) (ISO) To segregate items into groups (3) See also paper throw. according to specified criteria. Sorting involves ordering, but need not in¬ slow time scale volve sequencing for the groups may Synonym for extended time scale. be arranged in an arbitrary order. (3) To arrange a set of items according to smooth keys which are used as a basis for To apply procedures that decrease or determining the sequence of the items, eliminate rapid fluctuations in data. e.g., to arrange the records of a per¬ sonnel file into alphabetical sequence snapshot dump by using the employee names as sort (1) (ISO) A dynamic dump of the con¬ keys. 142 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

(4) Synonym for order. chanically recorded data that is to be (5) See balanced merge sort, bubble sort, subsequently punched into the same card. exchange sort, external sort, insertion

sort, internal sort, merge sort, mul¬ source language tipass sort, oscillating sort, polyphase (ISO) A language from which statements sort, repeated selection sort, selection are translated. sort, serial sort, sifting sort, tourna¬ ment sort, unbalanced merge sort. source program (1) (ISO) A computer program expressed sorter in a source language. (1) (ISO) A device that deposits punched (2) Contrast with object program. cards in pockets selected according to the hole patterns in the cards. (2) A person, device, or computer routine SP that sorts. (ISO) The space character. (3) (ISO) Deprecated term for sort pro¬ gram. space (1) A site intended for the storage of sorting program data, e.g., a site on a printed page or (ISO) Synonym for sort program. a location in a storage medium. (2) A basic unit of area, usually the size sort key of a single character. (1) A key used as a basis for determining (3) One or more space characters. the sequence of items in a set. (4) To advance the reading or display po¬ (2) One or more keys within an item, sition according to a prescribed for¬ used as a basis for determining the mat, e.g., to advance the printing or sequencing of items in a set. display position horizontally to the Synonymous with sequencing key. right or vertically down. (5) Contrast with backspace. sort pass (6) See working space. During the execution of a sort program, a single processing of all items of a set for the purpose of reducing the number of space character (SP) strings of items and increasing the number (1) (ISO) A character that is usually of items per string. represented by a blank site in a series of graphics. The space character,

sort program though not a control character, has a (ISO) A computer program that sorts function equivalent to that of a format items of data. Synonymous with sorting effector that causes the print or dis¬ program. play position to move one position forward without producing the printing source or display of any graphic. Similarly, See data source, message source. the space character may have a func¬ tion equivalent to that of an informa¬ source data card tion separator. A card which contains manually or me¬ (2) See also null character. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 143

span stability (1) (ISO) The difference between the See computational stability, light stability. highest and the lowest values that a quantity or function may take. stable state (2) See error span. (ISO) In a trigger circuit, a state in which the circuit remains until the application of a suitable pulse. special character (ISO) A graphic character in a character stack set that is not a letter, not a digit, and (ISO) Synonym for pushdown list. not a space character.

stacker special purpose computer See card stacker. (ISO) A computer that is designed to op¬ erate upon a restricted class of problems. standard form (ISO) Synonym for normalized form. specific address

Synonym for absolute address (1). standardize (ISO) Synonym for normalize. specific coding

Synonym for absolute coding. standing-on-nines carry (ISO) In parallel addition of numbers spectral response represented by decimal numerals, a proce¬ The variation in sensitivity of a device to dure in which a carry input to a given di¬ light of different wavelengths. git place is bypassed to the next digit place. If the current sum in the given di¬

spool git place is nine, the nine is changed to See tape spool. zero.

spooling start-of-heading character (SOH) (ISO) A transmission control character (ISO) the reading of output from and the used as the first character of a message writing of input onto auxiliary storage heading. concurrently with job execution in a form suitable for later processing or output op¬ start-of-text character (STX) erations. (ISO) A transmission control character that precedes a text and may be used to spot punch terminate the message heading. A device for punching one hole at a time

in a data medium. start signal A signal to a receiving mechanism to get spread ready to receive data or perform a func¬ (ISO) Synonym for irrelevance. tion.

sprocket holes statement Synonym for feed holes. (1) (ISO) In a programming language, a 144 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

meaningful expression that may de¬ step scribe or specify operations and is (1) One operation in a computer routine. complete in the context of this pro¬ (2) To cause a computer to execute one gramming language. operation. (2) In computer programming, a symbol (3) See job step, single step. string or other arrangement of sym¬ bols. step-by-step operation (3) (ISO) Deprecated term for instruction. (ISO) Synonym for single-step operation. (4) See assignment statement, conditional statement, job control statement. stop instruction (ISO) An exit that specifies the termina¬ static dump tion of the execution of a computer pro¬ (ISO) A dump that is performed at a gram. particular point in time with respect to a machine run, frequently at the end of a stop signal run, and usually under the control of the A signal to a receiving mechanism to wait computer operator or supervisory program. for the next signal.

staticize storage (1) To convert serial or time-dependent (1) (ISO) The action of placing data into parallel data into static form. a storage device and retaining them (2) Loosely, to retrieve an instruction and for subsequent use. its operands from storage prior to its (2) The retention of data in a storage de¬ execution. vice. (3) A storage device. (4) See acoustic storage, associative stor¬ static magnetic cell age, auxiliary storage, buffer storage, (ISO) Synonym for magnetic cell. capacitor storage, cathode ray storage, circulating storage, core storage, cryo¬ static storage genic storage, delay line storage, direct Storage other than dynamic storage. access storage, dynamic storage, elec¬ trostatic storage, erasable storage, ex¬ station ternal storage, fixed storage, immedi¬ See inquiry station, read station, remote ate access storage, internal storage, station, tape station. magnetic card storage, magnetic core storage, magnetic disk storage, mag¬ stationary information source netic drum storage, magnetic storage, (ISO) Synonymous with stationary mes¬ magnetic thin-film storage, magnetic sage source. wire storage, main storage, mass stor¬ age, matrix storage, mercury storage, stationary message source n-core-per-bit storage, nonvolatile stor¬ (ISO) A message source each message of age, one-core-per-bit storage, parallel which has a probability of occurrence in¬ search storage, parallel storage, perma¬ dependent of the time of its occurrence. nent storage, pushdown storage, push¬ Synonymous with stationary information up storage, real storage, serial access source. storage, static storage, temporary stor- AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 145

age, virtual storage, volatile storage, ly execute these instructions. Synonymous word-organized storage. with programmed computer.

storage allocation straight line coding (1) (ISO) The assignment of storage areas (1) (ISO) A set of instructions in which to specified data. there are no loops. (2) See dynamic storage allocation. (2) (ISO) A programming technique in which loops are avoided by unwind¬ storage capacity ing. (ISO) The number of bits, characters, bytes, words, or other units of data that a stratified language particular storage device can contain. (1) (ISO) A language that cannot be used as its own metalanguage, e.g., FOR¬ storage cell TRAN. (ISO) An elementary unit of a storage de¬ (2) Contrast with unstratified language. vice, e.g., a binary cell. string storage device (1) (ISO) A linear sequence of entities (ISO) A functional unit into which data such as characters or physical ele¬ can be entered, in which they can be re¬ ments. tained, and from which they can be re¬ (2) See alphabetic string, binary element trieved. string, bit string, character string, null string, symbol string, unit string. storage location (ISO) An area in a storage device, usually striping one that can be explicitly and uniquely In flowcharting, the use of a line across specified by means of an address. the upper part of a flowchart symbol to signify that a detailed representation of a storage protection function is located elsewhere in the same An arrangement for preventing access to set of flowcharts. storage for either reading, or writing, or both. stroke In character recognition, a straight line or store arc used as a segment of a graphic (1) (ISO) To enter data into a storage character. device or to retain data in a storage device. stroke centerline (2) (ISO) In computer programming, to In character recognition, a line midway copy data from registers into internal between the two stroke edges. storage. stroke edge stored program computer In character recognition, the line of dis¬ (ISO) A computer controlled by internally continuity between a side of a stroke and stored instructions, that can synthesize and the background, obtained by averaging, store instructions, and that can subsequent¬ over the length of the stroke, the ir- 146 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

regularities resulting from the printing and (2) See alphabetic character subset, al¬ detecting processes. phanumeric character subset, character subset, numeric character subset, prop¬ stroke width er subset. In character recognition, the distance mea¬ sured perpendicularly to the stroke center- substitute character (SUB) line between the two stroke edges. (ISO) A control character used in the place of a character that is recognized to stub card be invalid or in error, or that cannot be A special purpose paper card that has a represented on a given device. separable stub attached to a general pur¬ pose paper card. A stub card may be a subtracter scored card. (1) (ISO) A device whose output data are a representation of the difference be¬ STX tween the numbers represented by its (ISO) The start-of-text character. input data. (2) See adder subtracter, full subtracter, stylus printer half subtracter. (ISO) Synonym for matrix printer.

subtrahend SUB (ISO) In a subtraction operation, the (ISO) The substitute character. number or quantity subtracted from the minuend. subroutine (1) (ISO) A sequenced set of statements suffix notation that may be used in one or more (ISO) Synonym for postfix notation. computer programs and at one or more points in a computer program. sum (2) A routine that can be part of another (ISO) The number or quantity that is the routine. result of the addition of two or more (3) See closed subroutine, dynamic sub¬ numbers or quantities. routine, open subroutine, recursive subroutine, reentrant subroutine. summary punch

subroutine call (ISO) A card punch that may be connect¬ The subroutine, in object coding, that per¬ ed to another device, such as a tabulator, forms the call function. to enter data that was calculated or sum¬ marized by the other device. subscript (ISO) A symbol that is associated with summation check the name of a set to identify a particular A check based on the formation of the subset or element. sum of the digits of a numeral. The sum of the individual digits is usually com¬ subset pared with a previously computed value. (1) (ISO) A set each element of which is an element of a specified other set. supervisor AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 147

(1) (ISO) Synonym for supervisory pro¬ switching element gram, supervisory routine. (ISO) Deprecated term for logic element. (2) See overlay supervisor. switching function supervisory program (ISO) A function that has only a finite (ISO) A computer program, usually part number of possible values and the in¬ of an operating system, that controls the dependent variables of which have only a execution of other computer programs and finite number of possible values. regulates the flow of work in a data proc¬ essing system. Synonymous with executive switching variable program, supervisor. (ISO) A variable that may take only a fi¬ nite number of possible values or states.

supervisory routine (ISO) A routine, usually part of an switchpoint (ISO) Synonym for switch (1). operating system, that controls the execu¬ tion of other routines and regulates the flow of work in a data processing system. syllable (ISO) A or a Synonymous with executive routine, super¬ character string binary ele¬ ment string in a word. visor.

symbol swapping (1) (ISO) A conventional representation of See page swapping. a concept or a representation of a concept upon which agreement has switch been reached. (1) (ISO) In a computer program, a (2) A representation of something by rea¬ parameter that controls branching and son of relationship, association, or is bound prior to the branchpoint be¬ convention. ing reached. Synonymous with (3) See abstract symbol, flowchart symbol, switchpoint. logic symbol, mnemonic symbol. (2) A device or programming technique for making a selection, e.g., a toggle, symbolic address a conditional jump. (ISO) An address expressed in a form convenient for computer programming. switch core

(ISO) A core in which the magnetic symbolic addressing material generally has a high residual flux (ISO) A method of addressing in which density and a high ratio of residual to the address part of an instruction contains saturated flux density with a threshold va¬ a symbolic address. lue of magnetizing force below which

switching does not occur. symbolic coding The preparation of routines and computer switch indicator programs in a symbolic language. (ISO) In computer programming, an in¬ dicator that determines or shows the set¬ symbolic language ting of a switch. Synonymous with flag. A programming language that expresses 148 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

addresses and operation codes of instruc¬ synchronism or synchronous correction tions in symbols convenient to humans may be achieved between data terminal rather than in machine language. equipment, particularly when no other character is being transmitted. symbolic logic (ISO) The discipline in which valid argu¬ synchronous operation ments and operations are dealt with using (1) (ISO) An operation that occurs regu¬ an artificial language designed to avoid larly or predictably with respect to the the ambiguities and logical inadequacies occurrence of a specified event in of natural languages. Synonymous with another process, e.g., the calling of an mathematical logic. input-output routine that receives con¬ trol at a pre-coded location in a com¬ symbol manipulation puter program. The processing of symbols that have no (2) A mode of operation in which each explicit numerical values. action is started by a clock.

symbol rank syntax (ISO) Synonym for digit place. (1) (ISO) The relationship among charac¬ ters or groups of characters, independ¬ symbol string ent of their meanings or the manner (ISO) A string consisting solely of sym¬ of their interpretation and use. bols. (2) The structure of expressions in a lan¬ guage. symmetric channel (3) The rules governing the structure of a See binary symmetric channel. language. (4) The relationships among symbols. SYN The synchronous idle character. syntax language A metalanguage used to specify or de¬ synchronization pulses scribe the syntax of another language. Pulses introduced by transmission equip¬ ment into the receiving equipment to keep synthetic address the two equipments operating in step. (ISO) Synonym for generated address.

synchronous computer system (1) (ISO) A computer in which each (1) (ISO) In data processing, a collection event, or the performance of any bas¬ of men, machines, and methods or¬ ic operation, is constrained to start on ganized to accomplish a set of specific signals from a clock and usually to functions. keep in step with them. (2) See data processing system, decimal (2) Contrast with asynchronous computer. numeration system, fixed-point re¬ presentation system, fixed-radix numer¬ synchronous idle character (SYN) ation system, information feedback (ISO) A transmission control character system, management information sys¬ used by synchronous data transmission tem, mixed-base numeration system, systems to provide a signal from which mixed-radix numeration, numeration AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 149

system, operating system, positional re¬ presentation system, programming sys¬ tem, pure binary numeration system, radix numeration system, variable- point representation system. 150 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

T tape deck (1) (ISO) Deprecated term for tape unit. (2) (ISO) Synonym for tape drive. tabSe (1) (ISO) An array of data each item of tape drive which may be unambiguously identi¬ (1) (ISO) A mechanism for controlling the fied by means of one or more argu¬ movement of magnetic tape. This ments. mechanism is commonly used to move (2) A collection of data in which each magnetic tape past a read head or item is uniquely identified by a label, write head, or to allow automatic by its position relative to the other rewinding. Synonymous with tape items, or by some other means. Sy¬ deck, tape transport. nonymous with dictionary. (2) (ISO) Deprecated term for tape unit. (3) See boolean operation table, decision table, function table, operation table, tape punch truth table. Synonym for receiving perforator.

table lookup tape spool (ISO) A procedure for obtaining the value (1) (ISO) A cylinder without flanges on corresponding to an argument from a ta¬ which punch tape may be wound. ble of values. (2) A coiled length of perforated tape.

table lookup instruction tape station (ISO) An instruction that initiates a table (ISO) Deprecated term for tape unit. lookup.

tape transport tabulate (1) (ISO) Deprecated term for tape unit. (1) To format data into a table. (2) (ISO) Synonym for tape drive. (2) To print totals.

tape unit tabulation character (1) (ISO) A device containing a tape See horizontal tabulation character, vertical drive, together with read heads and tabulation character. write heads and associated controls. (2) See magnetic tape unit. tag

(ISO) One or more characters, attached to target language a set of data, that contains information (ISO) A language into which statements about the set, including its identification. are translated. Synonymous with object language. tape See carriage control tape, chadless tape, target program magnetic tape, perforated tape. (ISO) A computer program in a target language that has been translated from a tape code source language. Synonymous with object See perforated tape code. program. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 151

task one of three values, plus or minus one (1) The basic unit of work from the quantum or zero. standpoint of a control program. (2) In a multiprogramming or multiproc¬ text essing environment, a computer pro¬ (1) In ASCII and data communication, a gram, or portion thereof, capable of sequence of characters treated as an being specified to the control program entity if preceded and terminated by as a unit of work. Tasks compete for one STX and one ETX communica¬ system resources. tion control character respectively. (2) Contrast with heading. tasking See multitasking. thin film Loosely, magnetic thin film. telecommunication (ISO) The transmission of signals over thin film storage long distances, such as by telegraph, ra¬ Loosely, magnetic thin film storage. dio, or television. three-address instruction temporary storage (ISO) An instruction that contains three In computer programming, storage loca¬ address parts. tions reserved for intermediate results. Synonymous with working storage. three-bit byte (ISO) Synonym for triplet. tens complement (ISO) The radix complement in the deci¬ three-input adder mal numeration system. Synonymous with Synonym for full adder. complement-on-ten. three-plus-one address instruction terminal (ISO) An instruction that contains three (1) A point in a system or communication address parts, the plus one address being network at which data can either en¬ that of the instruction that is to be ex¬ ter or leave. ecuted next unless otherwise specified. (2) See data terminal equipment, user ter¬ minal. threshold (1) A logic operator having the property ternary that if P is a statement, Q is a state¬ (1) (ISO) Pertaining to a selection, choice, ment, R is a statement,..., then the or condition that has three possible threshold of P, Q, R,... is true if at different values or states. least N statements are true, false if (2) (ISO) Pertaining to a fixed radix nu¬ less than N statements are true, where meration system having a radix of N is a specified nonnegative integer three. called the threshold condition. (2) The threshold condition as in (1). ternary incremental representation (ISO) Incremental representation in which threshold element the value of an increment is rounded to (1) (ISO) A logic element that performs a 152 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

threshold operation. Synonymous with to measure time. Synonymous with clock threshold gate. register, time register. (2) A device that performs the logic thre¬ shold operation but in which the truth time register of each input statement contributes, to (ISO) Synonym for timer. the output determination, a weight as¬ sociated with that statement. time scale See extended time scale, fast time scale, threshold function variable time scale. (ISO) A two-valued switching function of one or more not necessarily boolean argu¬ time scale factor ments that take the value one if a speci¬ In simulation, the ratio of computer time fied mathematical function of the argu¬ to the corresponding problem time. ments exceeds a given threshold value, and zero otherwise. time share To use a device for two or more inter¬

threshold gate leaved purposes. (ISO) Synonym for threshold element. time sharing (1) (ISO) A mode of operation that pro¬ threshold operation vides for the interleaving of two or (ISO) An operation performed on ope¬ more independent processes on one rands to obtain a value of a threshold functional unit. function. (2) Pertaining to the interleaved use of time on a computing system that ena¬ throughput bles two or more users to execute A measure of the amount of work per¬ computer programs concurrently. formed by a computing system over a (3) (ISO) Deprecated term for conversa¬ given period of time, e.g., jobs per day. tional mode.

time toggle See access time, available time, compiling (1) Pertaining to any device having two time, computer time, corrective mainte¬ stable states. nance time, cycle time, deferred mainte¬ (2) Synonym for flip-flop. nance time, development time, downtime,

emergency maintenance time, idle time, tournament sort installation time, maintenance time, make¬ A repeated selection sort in which each up time, operating time, preventive subset consists of no more than two items. maintenance time, problem time, produc¬

tion time, program development time, pro¬ trace gram execution time, real time, translating A record of the execution of a computer time, word time. program; it exhibits the sequences in which the instructions were executed. timer (ISO) A register whose content is changed trace program at regular intervals in such a manner as (ISO) A computer program that performs AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 153

a check on another computer program by transcribe exhibiting the sequence in which the in¬ (ISO) To transmit data from one data structions are executed and usually the re¬ medium to another, converting them as sults of executing the instructions. necessary for acceptance by the receiving medium. tracing routine A routine that provides an historical re¬ transducer cord of specified events in the execution A device for converting energy from one of a computer program. form to another.

track transfer (1) The portion of a moving data medi¬ (1) (ISO) To send data from one place um, such as a drum, tape, or disk, and to receive the data at another that is accessible to a given reading place. Synonymous with move. head position. (2) (ISO) Deprecated term for jump. (2) See address track, card track, clock (3) See block transfer, peripheral transfer, track, feed track, regenerative track. radial transfer.

track pitch transfer check (ISO) The distance between corresponding A check on the accuracy of a data trans¬ points of adjacent tracks. fer.

trailer card transfer instruction A card that contains information related (ISO) Deprecated term for jump instruc¬ to the data on the preceding cards. tion.

trailing decision transfer interpreter (1) A loop control that is executed after (ISO) A device that prints on a punched the loop body. card characters equivalent to hole patterns (2) Contrast with leading decision. in another card.

trailing end transferred information The end of a perforated tape that last en¬ (ISO) Synonym for transinformation con¬ ters a perforated-tape reader. tent.

trailing zero transfer time In positional notation, a zero in a less sig¬ (ISO) The time interval between the in¬ nificant digit place than the digit place of stant the transfer of data starts and the the least significant nonzero digit of a nu¬ instant the transfer is completed. meral. transform transaction file (1) (ISO) To change the form of data ac¬ (ISO) A file containing relatively transient cording to specified rules, without sig¬ data, that, for a given application, is proc¬ nificantly changing the meaning of the essed together with the appropriate master data. file. Synonymous with detail file. (2) Synonymous with convert. 154 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

transformation (2) See character mean transinformation See key transformation, signal transforma¬ content, mean transinformation con¬ tion. tent.

transinformation content transinformation rate (1) (ISO) In information theory, the dif¬ See average transinformation rate. ference between the information con¬

tent conveyed by the occurrence of an translate event and the conditional information (ISO) To transform data from one lan¬ content conveyed by the occurrence of guage to another. the same event, given the occurrence

of another event; in mathematical no¬ translate duration tation, let: (ISO) Synonym for translating time.

xpy. be a pair of events, such as an translate phase input message x( and an output mes¬ (ISO) Of a run, the logical subdivision sage y. that includes the execution of the transla¬ tor. Synonymous with translating phase. plx^) the joint probability of the oc¬ currence of both events translating phase (ISO) Synonym for translate phase. p(x; |y ) the conditional probability of the occurrence of the event x(, given translating program the occurrence of the event yj (ISO) Synonym for translator.

p(y jx^ the conditional probability of translating time the occurrence of the event y., given (ISO) The elapsed time taken for the exe¬ the occurrence of the event x; cution of a translator. Synonymous with translate duration. p(xt) the probability of the occurrence of event x( translator (ISO) A computer program that translates p(y.) the probability of the occurrence from one language into another language of event y. and in particular from one programming

Then this difference T(x; Jy^) for the language into another programming lan¬ pair of events x;,y. is expressed as: guage. Synonymous with translating pro¬

i i gram. T(xj\yj) = \og , - '°9 p(x \y.J

transliterate p(x; I y.) P ply I x I = log log-1— log-—— = T(yj\x.) (1) (ISO) To convert data character by P character. Synonymous with mutual information, (2) To convert the characters of one al¬ transferred information, transmitted in¬ phabet to the corresponding characters formation. of another alphabet. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 155

transmission trigger circuit (1) The sending of data to one or more A circuit that has a number of stable locations or recipients. states or unstable states, at least one be¬ (2) The sending of data from one place ing stable, and designed so that a desired for reception elsewhere. transition can be initiated by the applica¬ (3) In ASCII and data communication, a tion of a suitable pulse. series of characters including headings

and texts. triple-length register (4) Synonymous with data transmission. (ISO) Three registers that function as a (5) See parallel transmission, serial trans¬ single register. Each register may be in¬ mission. dividually accessed. Synonymous with tri¬ ple register. transmission-block character See end-of-transmission-block character. triple-precision (ISO) Pertaining to the use of three com¬ transmission control character puter words to represent a number in ac¬ (ISO) Any control character used to con¬ cordance with the required precision. trol or facilitate transmission of data be¬ tween data terminal equipments. Synony¬ triple register mous with communication control charac¬ (ISO) Synonym for tnple-length register. ter.

triplet transmit (ISO) A byte composed of three binary To send data from one place for recep¬ elements. Synonymous with three-bit byte. tion elsewhere.

true complement transmitted information (ISO) Deprecated term for radix comple¬ (ISO) Synonym for transinformation con¬ ment. tent.

truncate transport To terminate a computational process in See tape device. accordance with some rule, e.g., to end the evaluation of a power series at a trap specified term. (ISO) An unprogrammed conditional jump to a specified address that is automatically activated by hardware, a recording being truncation made of the location from which the (1) (ISO) The deletion or omission of a jump occurred. leading or of a trailing portion of a string in accordance with specified

trigger criteria. (ISO) To cause the immediate execution (2) (ISO) The termination of a computa¬ of a computer program, often by interven¬ tion process, before its final conclusion tion from the external environment, for or natural termination, if any, in ac¬ example by means of a manually con¬ cordance with specified rules. trolled jump to an entry point. Contrast with round. 156 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

truncation error two-out-of-five code

(ISO) An error due to truncation. (1) (ISO) A binary-coded decimal nota¬ tion in which each decimal digit is truth table represented by a binary numeral con¬ (1) (ISO) An operation table for a logic sisting of five bits of which two are operation. (2) A table that describes a logic function of one kind, conventionally ones, and by listing all possible combinations of three are of the other kind, conven¬ input values and indicating, for each tionally zeros. The usual weights are combination, the true output values. 0-1-2-3-6 except for the representation

of zero which is then 01100. turing machine (2) A positional notation in which each (1) A mathematical model of a device decimal digit is represented by five bi¬ that changes its internal state and reads from, writes on, and moves a nary digits of which two are one kind potentially infinite tape, all in accord¬ (e.g., ones) and three are the other ance with its present state, thereby kind (e.g., zeros). constituting a model for computerAike behavior. two-plus-one address instruction (2) See universal tunng machine. (ISO) An instruction that contains three

turnaround time address parts, the plus-one address being (ISO) The elapsed time between submis¬ that of the instruction that is to be ex¬ sion of a job and the return of complete ecuted next unless otherwise specified. results.

twos complement twelve-punch (ISO) The radix complement in the pure A punch in the top row of a Hollerith card. Synonymous with y-punch. binary numeration system. Synonymous with complement-on-two. two-address instruction (ISO) An instruction that contains two ad¬ type bar dress parts. (ISO) A bar, usually mounted on an im¬ pact printer that holds type slugs. two-bit byte (ISO) Synonym for doublet. type font

two-input adder Type of a given size and style, e.g., (ISO) Synonym for half adder. 10-point Bodoni Modern.

two-level address An indirect address that specifies two lev¬ type wheel els of addressing. (ISO) Synonym for print wheel. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 157

u underflow See arithmetic underflow.

ultrafiche unit (ISO) In micrographics, microfiche with (1) A device having a special function. images reduced more than ninety times. (2) A basic element. (3) See arithmetic and logic unit, arith¬ unary operation metic unit, central processing unit, (ISO) Synonym for monadic operation. functional unit, information content natural unit, input-output unit, input unary operator unit, logic unit, magnetic tape unit, (ISO) Synonym for monadic operator. main control unit, output unit, peri¬ pheral control unit, tape unit. unbalanced merge sort (1) A merge sort, which is an external unit separator character (US) sort, such that the sorted subsets (ISO) The information separator intended created by the internal sorts are une¬ to identify a logical boundary between qually distributed among some of the units. available auxiliary storage devices. The subsets are merged onto the unit string remaining auxiliary storage devices (ISO) A string consisting of only one and the process repeated until all entity. items are in one sorted set.

(2) Contrast with balanced merge sort. universal set (ISO) The set that includes all of the ele¬ unconditional branch instruction ments of concern in a given study. (ISO) Deprecated term for unconditional

jump instruction. universal turing machine A turing machine that can simulate any unconditional control transfer instruction other turing machine. (ISO) Deprecated term for unconditional

jump instruction. unmodified instruction (ISO) Deprecated term for presumptive unconditional jump instruction. (ISO) A jump that takes place whenever the instruction that specified it is executed. unpack (ISO) To recover the original form of the unconditional jump instruction data from packed data. (ISO) An instruction that specifies an un¬ conditional jump. unstable state In a trigger circuit, a state in which the unconditional transfer instruction circuit remains for a finite period of time (ISO) Deprecated term for unconditional at the end of which it returns to a stable jump instruction. state without the application of a pulse. 158 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

unstratified language US

(1) (ISO) A language that can be used as The unit separator character. its own metalanguage, e.g., most natu¬ USASCII ral languages. Deprecated term for ASCII. (2) Contrast with stratified language.

user terminal unwind (ISO) An input-output unit by which a (ISO) To state explicitly and in full, with¬ user communicates with an automatic data out the use of modifiers, all the instruc¬ processing system. tions that are involved in the execution of utility program a loop. (ISO) A computer program in general support of the processes of a computer; upper curtate for instance, a diagnostic program, a trace The adjacent card rows at the top of a program, a sort program. Synonymous punch card. with service program.

utility routine uptime (ISO) A routine in general support of the (1) (ISO) Deprecated term for available processes of a computer; for instance, an time. input routine. Synonymous with service (2) (ISO) Synonym for operating time. routine. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 159

V Veitch diagram (1) (ISO) A means of representing boo¬ lean functions in which the number of validation variables determines the number of The checking of data for correctness, or squares in the diagram; the number of compliance with applicable standards, squares needed is the number of poss¬ rules, and conventions. ible states, i.e., two, raised to a power determined by the number of varia¬ variable bles. (1) (ISO) In computer programming, a (2) See also Venn diagram. character or group of characters that refers to a value and, in the execution Venn diagram of a computer program, corresponds (1) (ISO) A diagram in which sets are to an address. represented by regions drawn on a (2) A quantity that can assume any of a surface. given set of values. (2) See also Veitch diagram. (3) See loop-control variable, switching variable. verge-punched card Synonym for edge-punched card. variable-length record

Pertaining to a file in which the records verifier need not be uniform in length. (ISO) A device that checks the correctness of transcribed data, usually by comparing variable-point representation with a second transcription of the same (1) A positional representation in which data or by comparing a retranscription the position of the radix point is ex¬ with the original data. plicitly indicated by a special character

at that position. verify (2) Contrast with floating-point representa¬ (1) To determine whether a transcription tion. of data or other operation has been accomplished accurately. variable-point representation system (2) To check the results of keypunching. (ISO) A radix numeration system in

which the radix point is explicitly indicat¬ vertical feed ed by a special character at that position. Pertaining to the entry of a punch card into a card feed with a short edge first. variable time scale In simulation, the time scale used in data vertical positions processing when the time scale factor is See addressable vertical positions. not constant during a run. vertical tabulation character (VT) vector (ISO) A format effector that causes the (1) (ISO) A quantity usually represented print or display position to move to the by an ordered set of numbers. corresponding position on the next of a (2) Contrast with scalar. series of predetermined lines. 160 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

virgin medium the computing system and by the amount (ISO) A data medium in or on which of auxiliary storage available, rather than data is not or has not been recorded. by the actual number of main storage locations. virtual address (ISO) The address of a notional storage location in virtual storage. void In character recognition, the inadvertent virtual memory absence of ink within a character outline. (ISO) Deprecated term for virtual storage.

virtual storage volatile storage The notion of space on storage devices (ISO) A storage whose content is lost

that may be regarded as main storage by when the power is removed. the user of a computing system, in which virtual addresses are mapped into real ad¬ dresses. The size of the virtual storage is VT limited only by the addressing scheme of The vertical tabulation character. AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING 161

w word time In a storage device that provides serial access to storage locations, the time inter¬ waiting time (ISO) Synonym for latency. val between the appearance of corre¬ sponding parts of successive words. weight (ISO) In a positional representation, the working area factor by which the value represented by (ISO) Synonym for working space. a character in the digit place is multiplied

to obtain its additive contribution in the working space representation of a real number. Synony¬ (ISO) That portion of main storage that mous with significance. is used by a computer program for tem¬ porary storage of data. Synonymous with who-are-you (WRU) See inquiry character. working area, working storage.

wire printer working storage (ISO) Synonym for matrix printer. (ISO) Synonym for temporary storage, working space. wire storage

See magnetic wire storage. write (ISO) To make a permanent or transient word recording of data in a storage device or (1) (ISO) A character string or a binary on a data medium. element string that it is convenient for some purpose to consider as an entity. (2) A character string or a bit string con¬ write cycle time sidered as an entity. (ISO) The mimmum time interval between (3) See alphabetic word, computer word, the starts of successive write cycles of a doubleword, halfword, index word, in¬ storage device with separate reading and struction word, machine word, numeric writing cycles. word, parameter word, reserved word.

write head word length A magnetic head that only writes. (ISO) The number of characters or of bi¬ nary elements in a word. writing

word-organized storage (ISO) The action of making a permanent (ISO) A storage in which only complete or transient recording of data in a storage words may be accessed at a time. device or on a data medium. 162 AMERICAN NATIONAL DICTIONARY FOR INFORMATION PROCESSING

X zerofill (ISO) To character fill with the represen¬ tation of the character zero. Synonymous X-datum line with zeroize. An imaginary line, used as a reference edge, along the top edge of a punch card, zeroize i.e., a line along the edge nearest the twelve-punch row of a Hollerith card. (ISO) Synonym for zerofill.

x-pumch zero address Synonym for eleven-punch. (ISO) Synonym for immediate address.

zero punch Y A punch in the third row from the top on a Hollerith card.

Y-dafum Sine An imaginary line, used as a reference zero suppression edge, passing along the right edge of a (ISO) The elimination from a numeral of punch card at right angles to the X-datum zeros that have no significance in the nu¬ line. meral. Zeros that have no significance in¬ clude those to the left of the nonzero di¬ y-punch gits in the integral part of a numeral and Synonym for twelve-punch. those to the right of the nonzero digits in the fractional part. Z zone punch (1) (ISO) A hole punched in one of the zero upper three card rows of a twelve-row (1) (ISO) In data processing, the number punch card. Synonymous with over¬ that, when added to or subtracted punch. from another number, does not alter (2) A hole punched in one of the punch the value of that other number. rows designated as twelve, eleven, or (2) See leading zero, trailing zero. zero, and sometimes eight or nine. A zero punch, and sometimes a nine- zero-address instruction punch, by itself, is considered a nu- (ISO) An instruction that contains no ad¬ m eric punch. dress part, and is used when the address (3) A zero punch in combination with a is implicit or when no address is required. numeric punch. (4) Contrast with digit punch.

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