Personal Computers

)0 /^09'S3 Center for Information Systems Research Massachusetts Institute of Technology Sloan School of Management 77 Massachusetts Avenue Cambridge, Massachusetts, 02139 PERSONAL COMPUTERS Hoo-min D. Toong Amar Gupta December 1982 CISR WP #99 Sloan WP //1409-83 Reprinted by permission Scientific American Center for Information Systems Research Sloan School of Management Massachusetts Institute of Technology 3129 Personal Computers by Hoo-min D. Toong and Amar Gupta SCIENTIFIC AMERICAN DECEMBER 1982 VOL. 247, NO. 6 PR 86- 107 PUBLISHED BY W. H. FREEMAN AND COMPANY 660 MARKET STREET, SAN FRANCISCO, CALIFORNIA 94104 Copyright 1982 by Scientific American. Inc All rights reserved Printed in the USA No part of this offprint may be reproduced by any mechanical, photo graphic or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted or otherwise copied for public or private use without written permission of the publisher. The trademark and tradename "SCIENTIFIC AMERICAN" and the distinctive logo- type pertaining thereto are the sole property of and are registered under the name of. and are used herein under license from. Scientific American, Inc . ' iÔmO^y, a^-fi^.: Sv EEil cirii 3r _-/-^ |T3jri-»'1J|'VrclI i v-_vB«'^; :i:Ei«^ m ^SB*- i'-M t'^r . _.^ „ •' • * m#ui2 _U100._ ^5JU13j^^lSj^-Û15^,ÛlB ;»"-.-« I- * ft'r. * 4 4 ; •' v« jiJ rl « -c : »> 1 at — 18'>0^0i' iaa ,t—y. -~' -lat'- i"" -1 • • •*/-. , • • * • ~~' ' ^— "=" rrX—.? nMJ^c a 'tWii'cj^»L'- ''r-'lfrij^-trri- .-I 'rT--l r r^r ~ ..i-i'-'MM'îi?' .* '7^' '-~: ••;"": ;'."~; ;">_-; •• •'-^ ,N : ': :'.T' •,;".; ;.T «ft- ;-r m' »î^.^r^ ._%*-•; 1 III I—M^3.i. Personal Computers An account of their hardware, software, applications and current proliferation. By making computers accessible to untrained people they promise to bring about the long-heralded computer revolution by Hoo-min D. Toong and Amar Gupta the aircraft industry had evolved as years. In the same period the cost, the for a department or a working group If spectacularly as the computer in- energy consumption and the size of within such an organization. Today the dustry over the past 25 years, a Boe- computers of comparable power have personal computer can serve as a work ing 767 would cost $500 today, and it decreased by a factor of 10,000. station for the individual. Moreover, would circle the globe in 20 minutes on The result is the advent of the person- just as it has become financially feasible five gallons of fuel. Such performance al computer, which for less than $500 to provide a computer for the individual would represent a rough analogue of the can put at the disposal of an individual worker, so also technical developments reduction in cost, the increase in speed about the same basic computing power have made the interface between man of operation and the decrease in energy as a mainframe computer did in the ear- and machine increasingly "friendly," so consumption of computers. The cost of ly 1960's and as a minicomputer did in that a wide array of computer functions computer logic devices is falling at the the early 1970"s. Twenty years ago the are now accessible to people with no rate of 25 percent per year and the cost cost of a computer could be justified technical background. of computer memory at the rate of 40 only if the machine met the needs of a The first personal computer was put percent per year. Computational speed large organization. The minicomputers on the market in 1975. By the end of has increased by a factor of 200 in 25 introduced in the 1970"s are appropriate this year more than a million personal computers will be in service in the U.S. CASSETTE INPUT/OUTPUT KEYBOARD INPUT OUTPUT alone. In 1981 total sales of personal computers and their accessories in the U.S. amounted to $2.2 billion; sales are expected to surpass $6 billion in 1985. INTEL There has been talk of a "computer rev- ' MICROPROCESSOR olution" ever since the electronics industry learned in the late 1950's to in- SLOTS FOR AUXILIARY- EXPANSION PROCESSOR SLOT scribe miniature electronic circuits on a MODULES chip of silicon. What has been witnessed CLOCK CAPACITOR so far has been a steady, albeit remark- , CLOCK OSCILLATOR ably speedy, evolution. With the pro- D SYSTEM-CONFIGURATION liferation of personal computers, how- SWITCHES ever, the way may indeed be open for a READ-ONLY true revolution in how business is con- MEMORY (ROM) TIMER INPUT/OUTPUT ducted, in how people organize their PORT personal affairs and perhaps even in how EXPANSION people think. DIRECT MEMORY SOCKET ACCESS Anatomy of a Computer D D ODD DDDDD D D A computer is essentially a machine that receives, stores, manipulates and RANDOM- TIME DELAYS. D DDDD D communicates information. It does so ACCESS DDDDDDD DEVICE DECODERS MEMORY (RAM) AND OTHER SUPPORT by breaking a task down into logical op- CIRCUITRY D DDDDDDDD DDDDDDD erations that can be carried out on binary numbers—strings of 0"s and Ts—and SPEAKER doing hundreds of thousands or mil- OUTPUT- D°DDDDD lions of such operations per second. At the heart of the computer is the central MAIN CIRCUIT BOARD of the IBM Personal Computer is shown in the photograph on the processing unit, which performs the ba- opposite page and its major elements are identified in the drawing above. The size of the board sic arithmetic and logic functions and is 8 /2 by 12 inches. To it are attached a large number of silicon chips carrying integrated cir- supervises the operation of the entire cuits; each chip is about a quarter of an inch square and is encased in a rectangular plastic pack- system. In a personal computer the cen- age fitted with electrodes. The chips and elements such as resistors and capacitors are intercon- tral processing is nected by conductors printed on the board. The microprocessor, the 16-bit 8088 made by the unit a microprocessor: Intel Corporation, has 20,000 transistors and operates at a frequency of almost five million cy- a single integrated circuit on a chip of cles per second. "System programs" are stored permanently in the read-only memory (ROM); silicon that is typically about a quar- random-access memory (RAM) stores programs and data that change from time to time. ter of an inch on a side. Other silicon chips constitute the computer's primary The core of the software is an "operat- define a personal computer as a system memory, whe _ both instructions and ing system" that controls the computer's that has all the following characteristics: data can be stored. Still other chips gov- operations and manages the How of in- 1. The price of a complete system is ern the input and oiUput of data and car- formation. The operating system medi- less than $5,()()(). ry out control operations. The chios ates between the machine and the hu- 2. The system either includes or can are mounted on a heavy plastic circuit man operator and between the machine be linked to secondary memory in the board; a printed pattern of conductors and an "application" program that en- form of cassette tapes or disks. interconnects the chips and supplies ables the computer to perform a specif- ?•. The microprocessor can support a them with power. The board is enclosed ic task: solving a differential equation, primary-memory capacity of 64 kilo- in a cabinet; in some instances there are calculating a payroll or editing a let- bytes or more. (A kilobyte is equal to several boards. ter. Programs are ordinarily stored in 2'0, or 1,024, bytes. A byte is a string of Information is entered into the com- secondary-memory media and are read eight bits, or binary digits. One byte can puter by means of a keyboard or is into the primary memory as they are represent one alphabetic character or transferred into it from secondary stor- needed for a particular application. one or two decimal digits. A 64-kilobyte age on magnetic tapes or disks. The memory can store 65,536 characters, or computer's output is displayed on a The Personal Computer some l(),0()() words of English text.) screen, either the computer's own cath- 4. The computer can handle at least ode-ray tube, called a monitor, or an A personal computer is a small com- one high-level language, such as Basic, ordinary television screen. The output puter based on a microprocessor; it is a Fortran or Cobol. In a language of this can also be printed on paper by a sep microcomputer. Not all microcomput- kind instructions can be formulated at a arate printer unit. The device called ers, however, are personal computers. A fairly high level of abstraction and with- a modem (for modulator-demodulator) microcomputer can be dedicated to out taking into account the detailed op- can be attached to convert the comput- a single task such as controlling a ma- erations of the hardware. er's digital signals into signals for trans- chine tool or metering the injection of 5. The operating system facilitates an mission over telephone lines. fuel into an automobile engine; it can interactive dialogue; the computer re- The chips and other electronic ele- be a word processor, a video game or sponds immediately (or at least quick- ments and the various peripheral devic- a "pocket computer" that is not quite ly) to the user's actions and requests. es constitute the computer's hardware.

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