SILICON COMPOSERS INC FAST Forth Native-Language Embedded Computers
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Harris RTX 2000"" l&bit Forth Chip SC32"" 32-bit Forth Microprocessor 08 or 10 MHz operation and 15 MIPS speed. 08 or 10 MHz operation and 15 MIPS speed. 1-cycle 16 x 16 = 32-bi multiply. 1-clock cycle instruction execution. 1-cycle 1&prioritized interrupts. *Contiguous 16 GB data and 2 GB code space. *two 256-word stack memories. *Stack depths limited only by available memory. -&channel 1/0 bus & 3 timer/counters. *Bus request/bus grant lines with on-chip tristate.
SC/FOX PCS (Parallel Coprocessor System) SC/FOX SBC32 (Single Board Computer32) *RTX 2000 industrial PGA CPU; 8 & 10 MHz. 032-bi SC32 industrial grade Forth PGA CPU. *System speed options: 8 or 10 MHz. *System speed options: 8 or 10 MHz. -32 KB to 1 MB 0-wait-state static RAM. 42 KB to 512 KB 0-wait-state static RAM. *Full-length PC/XT/AT plug-in (&layer) board. .100mm x 160mm Eurocard size (+layer) board.
SC/FOX VME SBC (Single Board Computer) SC/FOX PCS32 (Parallel Coprocessor Sys) *RTX 2000 industrial PGA CPU; 8, 10, 12 MHz. 032-bi SC32 industrial grade Forth PGA CPU. *Bus Master, System Controller, or Bus Slave. *System speed options: 8 or 10 MHz. Up to 640 KB 0-wait-state static RAM. 064 KB to 1 MB 0-wait-state static RAM. -233mm x 160mm 6U size (Slayer) board. *FulClength PC/XT/AT plug-in (Slayer) board.
SC/FOX CUB (Single Board Computer) SC/FOX SBC (Single Board Computer) *RTX 2000 PLCC or 2001A PLCC chip. *RTX 2000 industrial grade PGA CPU. -System speed options: 8, 10, or 12 MHz. *System speed options: 8, 10, or 12 MHz. -32 KB to 256 KB 0-wait-state SRAM. *32 KB to 512 KB 0-wait-state static RAM. 100mm x lmmm size (&layer) board. *100mm x 160mm Eurocard size (+layer) board.
For additional product information and OEM pricing, please contact us at: SILICON COMPOSERS INC 208 California Avenue, Palo Alto, CA 94306 (415) 322-8763 Features Character Classification 6 Charles Curley "In the words of Arlo Guthrie, I'm not proud." While the author was implementing Martin Schaaf's "Formatted Input Fields," in true Forth-hacker fashion he found some improvements to make. The resulting utility provides a simple way for applications programmers to classify characters: printable, control, upper case, etc. Borrowing a useful C routine via reverse engineering along the way, he even fine-tuned that.
UN*X Tools Used on the FSAT Project 9 Jim Schneider Continuing the work to provide a Forth environment that incorporates the best features of UWX.. . This is the first of two installments that introduce the particular UN'X tools which will be cited later in the series, i.e., the programming commands rn4(11, sh(l1, and make(1). "If you want to swim, you're going to get wet," so roll up your sleeves for a crash course. You'll learn something about the UN'X world and probably will appreciate Forth-like simplicity even more!
INTRAN-an Integer Formula manslator 16 J. V Noble To properly extend Forth to accept ordinary, infix mathematical expressions as input and compile a reliable Forth equivalent, the programmer must design a simple user interface; allow easy porting, maintenance, and extension; and include bulletprooferror handling. The author of Scientif~cForth provides this recursive, integer expression parser that directly represents the Backus-Naur statement of its grammar as Forth code.
Terminal Input and Output
Telephone numbers, social security numbers, times and dates, and a myriad of other kinds of information have specific formatting conventions that make it easier to read and use them I accurately. This, the sixth in a series of Forth tutorials, teaches Forth methods of formatting strings of numbers. Adding to the ability to simply display numerical dlgits, the neophyte programmer now learns how to present them clearly for practical use by the end user.
Departments 1
4 Editorial ...... Why FIG Chapters?
5 Letters ...... Ready to pay; More good results with Forth.
31 Fast Forthward ...... The Point of No Return
34 resource Listings ...... FIG chapters
38 Advertisers lndex
39 On the Back Burner ... Who's on First?
1 I Forth Dimensions 3 September 1993 October Forth Dimensions Volume XV, Number 3 September 1993 October
Published by the Why FIG Chapters? Forth Interest Grouv The newly formed Southern Wisconsin chapter of the Forth Interest Group describes what Editor happened at one of their first meetings: Marlin Ouverson Circulation/Or&r Desk "After about half an hour of conversation, Dave Ruske spoke about the use of Forth in Frank Hall two embedded applications for ICOM, Inc. The first was an 8031-based operator access panel for an Allen-Bradley PLC-2; the second was a driver that loads onto the Allen-Bradley KT card Forth Dimensions welcomes (a Z80-based network card for PLC communications). LMI metacompilers were used on both letters to the tor, and comments from its readers. projects. No responsibility is assumed for "Dr. Bob Lowenstein of Yerkes Observatory told the group about Yerk and how it is acaracy ofsubmisSiom. applied to telescope control and data acquisition. Yerk is an object-oriented Forth variant for subsaiptiontofirth~i-~ the Mac, a public-domain product derived from Neon. One of the things Dr. Lowenstein uses isincludedwithmembership Forth Interest Group at $40 per this for is remotely controlling a telescope in New Mexico via the Internet. Yerk software will year ($52 air). For mem- also be used to control two new telescopes being built at the South Pole. bership, change of address, and to "Matt Mercaldo showed and talked about the Modular Micro~rocessorTrainer being- ( submit items for publication, the ( developed for use at Johns Hopkins University. The unit uses two ~otorola~C68HCllA8s is: Forth interest P.O. Box 21 54, Oakland, California with New Micros' Max-Forth on chip. The student can prototype projects on the unit and 94621, Administrative 510- communicate with it using a terminal, or with a keyboard and built-in LCD. Matt provided 89-FORTH. Fax: 510-535-1295. the group with copies of a paper describing his work. / Advertising sales: 805-946-2272. 1 "Glenn Szejna described his use of Forth at Nicolet Instruments. Several people in the Copyright @ 1993 by Forth In- group had used Nicolet oscilloscopes, unaware that Glenn's Forth code was running under terest GrouD. Inc,Thematerialcon- . , the hood. tained in this periodical (but not "Scott Woods discussed his use of Forth, including- his current -.project, firmware for an the code) is copyrighted by the industrial metal detector. This device will be used for such things as preventing machine authors Of the and by Forth Interest Group, Inc., screws from showing up in your breakfast cereal. respectively. ~nyreproduction or "Olaf Meding described Amtelco's use of polyForth in programming their Systems for use of this ~eriodiulas it is com- telephone answering services [see "~orth-~asedMessage ~ekice,"Forth DimensionsXIV/5]. I piled or thd artides, except repro- / a he-Arntelco EVE (Electronic Video Exchange) is the largest and most sophisticated system ductiOm non-commercial pur- poses, without the written permis- of its kind, and has gained 70% of the answering service market. sion of Forth Interest Group, Inc. is "James Heichek demonstrated VORCOMP, a public-domain directory and file-compare a violation of the Copyright.. - I~WS. utility written in his own version of Forth. James talked about why he believed the stack Any code bearing a copyright no- manipulation words in Forth became a hindrance to his work, and about how he added local lice> un be used Only with permission of the copyright variables to clean up hs code. He is currently developing educational software. holder. "Olaf Meding gave a brief tour of the 'Introduction to Forth' disk and demonstrated loading C.H. Ting's tutorial in F-PC. Along the way, the F-PC single-step debugger was also The Forth Interest Group demonstrated. The Fonh Interest Group is the association of programmers, man- "[Asl the meeting began to break up, Dr. Lowenstein took some time to demonstrate Yerk agers, and engineers who create and to impart some insider information to Paul Anderson. Paul is new to Forth and plans to Dractiul, ~~~h-b~~~dsolutions to build a system to monitor and control model railroads via a Mac." real-world needs. Many research 1 -hardware and software desinns- that will advance the general state of Thanks to Dave Ruske for providing these notes, and congratulations to the Southern the art, FIG provides a dimate of Wisconsin FIG Chapter for forming what is obviously a dynamic and resource-rich group. intenectual exchange and benefits It was only a few months earlier that these folks contacted the FIG office for a Chapter kit. I intended to assist each of its mem- I If there is no FIG Chapter in your area, perhaps you should think of doing the same.. . bers. Publications, conferences, seminars,telecommunications, and Regularly scheduled meetings; guest lecturers; planned presentations and demonstra- area chapter meetings are among tions; advance mailing of meeting details; and plenty of interaction, flexibility,and attention i~ activities, to the particular needs and interests of your groupperhaps including occasional tutorials or ongoing classes for Forth neophytes-are elements that keep chapter meetings lively and Dimensions (ISSN 08% 0822) is published bimonthly for useful. If there is already a chapter near you, think about how your added participation might $40/46,52 per by the Forth help that group, then talk to the chapter's officers and organizers about volunteering- I~~,,,,, Group,. . TPI, 1293 old whether as stamp-licker, secretary, emcee, program chairman, snack officer, or next chapter Mt. view-~lviso~d., sumyvale, president. CA 94089. Second-dass postage paid at San Jose, CA. POSTMAS- Who knows, maybe you'll even discover-like at least one Forth author-that steady TER:SendaddresschangestoForth Forth-related employment is a fringe benefit of the contacts made at your local FIG Chapter. Di-iom, P.O. 2154, Oak- -Madin Ouuerson ) land, CA 94621 ." I September 1993 October 4 Forth Dimensions classes. I find that I can do projects in days and weeks, instead of months, by using scripting languages. With Forth as a platform, this will be even better. I am ready to pay money for natWF now. When can I get it?
Sincerely, Letters to the Editor-and to your fellow readers-are always welcome. Mark Martino Respond to articles, describe your latest projects, ask for input, advise 14115 NE 78th Court the Forth community, or simply share a recent insight. Code is also Redmond, WA 78052 welcome, but is optional. Letters may be edited for clarity andlength. We want to hear from you! More Good Results with Forth Dear Mr. Ouverson: I am not in the habit of writing letters to the editor, but the excellent article by Donald Kenney ("Forth in Search of a Ready to Pay Job," FD XV/l) has prompted me to do it. Dear Marlin: The attached memo 1notprintedh~Ed.lresultedfrom Thanks to Markus Dahm for contributing the article about the fact that the customer, another division of the same natWF in your last issue (FDXV/2). I've dabbled in Forth corporation, wanted to use Forth in an automotive controller since I was a hardware engineer, and this development is we were designing. The project ended up using a dialect of exciting for a lot of reasons. My current work involves Modula-2. developing presentations andvisual interfaces. I use SuperTalk, Now working for a dfferent corporation, I use Forth quite HyperTalk, Openscript, and, if I have to, C++.The first two frequently for manufacturing automation, with good results. run on the Mac, the third on the PC. All three are very similar The language is very practical for our application (STD-based to each other and, it turns out, to natOOF. controllers for various machines), thanks to its ease and The concept of natWF is exciting because it means that speed of coding, speed of execution, and elimination of the a scripting language based on Forth is being created that has need for logic state analyzers, in-circuit emulators, and all the a good chance of wide and profitable acceptance by the other rather expensive peripherals required with most high- public and by the software development community. It is the level languages. Very few programmers are involved (a must ideal way to bypass the engineers and managers who don't with Forth, in my view), and the typical application requires understand Forth, and to take it directly to the public. It is also only about 500 lines of code. a good platform for a visual programming language and for We use a PC for development, and transfer the code over visual interfaces in general. an RS-232 port to the PROM-based controller, which com- It is particularly exciting to me because I can have a simple piles it. The same port is used to communicate with the scripting language, natWF, based on a simple machine running application during debugging. After release, the controllers work in standalone mode (no PC); if anything needs to be changed, or if we need to intervene in order to I use Forth quite frequently for facilitate mechanical adjustments, we take a laptop up to the manufacturing automation, controller and connect it to the port, making it interactive with good results. again. A battery-backed RAM (Dallas Semiconductor) in the The language is very practical program memory chip socket during code development for our application eliminates having to wait for the program to reloadevery time ... the power is turned off. After release, a PROM can replace model, Forth. This means that, unlike the other scripting that RAM if frequent changes are not anticipated. In one languages, I will be able to easily create new methods and controller, where some variables may need to be preserved whatever classes of objects I need. I will also have access to after a reset, the program is allowed to allocate battery- the underlying architecture of the machine if I need it. This backed program memory for those variables, thanks to the is particularly helpful when tracking down the memory versatility of the system. problems that come up (scripting languages still seem to mess up memory handling). Sincerely yours, Those other scripting languages provide the user with a Ivan C. Coelho limited, albeit flexible, set of classes. Until recently, any Manufacturing Engineering Manager compilation had to be done by creating XCMDs or DLIs in Joslyn Electronic Systems another language, usually C. Heizer Software now provides 6868 Cortona Drive a product that allows you to create XCMDs using HyperTalk Goleta, California 73116-0817 itself; however, one cannot create new classes or modify old
Forth Dimensions 5 September 1993 October Character Classification Reverse Engineering a C Utility
Charles Curley Gillette, Wyoming
A simple means of allowing applications programmers to Reverse Software Engineering class@ characters (printable, control, upper case, etc.) is shown. The first thing I did was examine the header file ctype.h. This consists almost entirely of a series of macro definitions Historical Note (#defines, in C-ese) for use with a lookup table called The version of Forth used here is fastForth, a 68000 JSW -ctype[l. (For those of you who don't speak C, that describes BSR-threaded Forth described in "Optimization Consider- a character array. On the 68000, that is a byte array as well. ations," Forth Dimensions XIV/5. There is minimal code The reason for the - (underscore) in the name has to do with specific to fastForth, and implementation on other Forths the kinky requirements of C linkers.) should be fairly easy. F@ is a fast, word-boundary-only The first group of macros defines a series of bit masks for version of @.Users of other Forths will have to adjust the use with the lookup table at -ctype. For example, a bit mask code. to identify upper-case characters might be defined as follows: #define -U 0 1 Background /* Upper-case alphabetic */ While implementing Martin Schaafs "Formatted Input Fields" (Forth DimensionsXV/l), I examined the code to see The second group defines a series of macros to classify how it was done. The code depended on three words for characters, using -ctype and the bit masks in the first group. detecting the classification of a character. These are: ALPHA, For example, to determine if a character is upper case, use ALPHA-NUMERIC, and NUMERIC. I thought the code for isuppea, which might be defined as follows: these words was a bit crude and could be better done. What #define isupper (c) (-ctype [ (c)+I1 &-U)
When I learned C, isuppea uses the character to be classified as an index into the table at -ctype to fetch a bit mask. This is anded bitwise the first thing I did was (the ampersand operator) with the mask defined above, -U, cure one of its lacks. to produce a flag. Ifbit 0 is set in that entry in the table, a result of 1 is returned by the macro, indicating that the test character is upper case. If bit 0 is reset, the character under test is not was needed, I thought, was a much more flexible system upper case. which could also be much faster. A look-up table would be Examination of the macros indicated one place where an just the thing. improvement could be made: the index into the array is Having worked in C, I knew exactly where to find such defined as (c)+l, which would involve at least one instruction a lookup table: C's library routines and macros as described to increment c. Why the table begins at -ctype+l instead of in the header file ctype.h. I decided to implement the C at -ctype itself is unknown. The reason is most likely lost routines in Forth. In the words ofArlo Guthrie, I'm not proud. among the antiquities of Bell Labs, along with the program- Or tired. Converting the routines and macros to Forth was ming languages A and B, and the Bell Labs version of the Ark easy. Duplicating the table was also easy, but only because of the Covenant. This instruction can be eliminated by I have experience with Forth and insisted years ago on curing starting the table at -ctype, so that is how the table will be at least one of the many problems with C. implemented in Forth. Yes, folks, I admit it: I actually found something done It would be possible to build the table at -ctype by better in C than in a Forth program. So one of the questions determining each character's mask, and building it by hand. I had was whether I could do a better job in Forth than the Instead, I chose to retain compatibility with C by carrying implementors of my C compiler had done in C. over the table in its entirety. Not having source for the table
September 1993 October 6 Forth Dimensions (one of the disadvantages of C Scr # 1920 libraries), I had to reverse en- 0 \ formatted input fields ( 21 5 93 CRC 18:07 ) 1 \ from article by Martin Schaff, 5,6 93 Forth Dimensions gineer it.' 2 forget task forth definitions : task ; Fortunately, I had a ready 3 solution to that problem. One 4 of the first things I did when I 5 base f@>r determined to learn C was to 6 cure one of its lacks. I wrote a 7 memory dump routine, with 8 1 12 tthru the idea that I could build it 9 into programs and get at least 10 11 some ability to see memory 12 modified as the program pro 13 r> base f! editor flush gressed. The syntax is: 14 dump(addS,len). Forthlike, 15 isn't it? An incredbly simple C pro- Scr # 1921 gram printed out a hex dump 0 \ ctype character classifier ( 21 5 93 CRC 18:07 ) of the array at -ctype. Using 1 create -ctype hex operating system indirection, I 2\ 0 1 2 3 4 5 6 7 wrote the output to a file. I 3 40 c, 40 c, 40 c, 40 c, 40 C, 40 c, 40 c, 40 c, 4 then referred to the output file 5\ 8 9 Oa Ob from time to time as I edited 6 40 c, 50 c, 50 c, 50 c, Forth screens to implement 7 the table in Forth. 8 \ 10 11 12 13 9 40 c, 40 c, 40 c, 40 c, The Forth Code 10 The Forth code is included 11 \ 18 19 1a lb lc Id 1e 1f in the fastForth implementa- 12 40 c, 40 c, 40 c, 40 c, 40 c, 40 c, 40 c, 40 c, 13 ;s This is a lookup table for examining characteristics tion of Mr. SchaaPs code, start- 14 of characters: alpha, numeric, printable, etc. ing on screen 1920. This screen 15 is a loader screen, and could contain a vocabulary declara- Scr # 1922 tion, if one wanted to hide the 0 \ ctype character classifier ( 21 5 93 CRC 18:07 ) code from the user. 1 \ b1 20 ! I, Y $ % & Screen 1921 begins the 2 90 C, 20 c, 20 c, 20 c, 20 c, 20 c, 20 c, 20 c, lookup table with the phrase 3 create -ctype on line one. 4\( 28) * + - / 5 20 c, 20 c, 20 c, 20 c, 20 c, 20 c, 20 c, 20 c, Each character position has 6 one hex value installed in it 7\0 301 2 3 4 5 6 7 with the word c, . Above it is 88c, 8c, Bc, 8c, 8c, 8c, 8c, 8c, a comment indicating the char- 9 acter that the entry represents. 10 \ 8 38 9 < - > ? For example, position zero, 118c, 8c, 20c, 20c, 20c, 20c, 20c, 20c, indicating ASCII value 0, has a 12 bit mask of hex 40, indicating 13 ;s The table and its usage are patterned after the C a control character. The tab 14 library routines for the same purpose. See ctype.h for more 15 details. character, ASCII 9, is both a control character and a white- Scr # 1923 space character, so its bit mask 0 \ ctype character classifier ( 21 5 93 CRC 18:07 ) is hex 50. The table continues l\@40A B C D E F G through screen 1924. 2 20 c, 1 c, 1 c, 1 c, 1 c, 1 c, 1 c, 1 c, The code that uses the table 3 is on the next screen, in the 4\H 481 J K L M word CLASSIFIER. This de- 5 1 c, 1 c, 1 c, 1 c, 1 c, 1 c, fining word builds a classifier 6 7\P 50Q R S T U 8 1 c, 1 c, 1 c, 1 c, 1 c, 1 c, 1. The names have been changed to 1 protect the publishers. Forth Dimensions 7 September 1993 October word, analogous to the sec- ond group of macros in ctype.h. On line five is code to build a header and comma a bit mask into the dictionary (see the stack diagram on line 13). Also on that line, and com- mented out, is a high-level Scr # 1924 DOES> portion of the code. 0 \ ctype character classifier 5 93 CRC 18:07 ) The code takes a value as l\@60a b c f 9 input, leaving the input value 2 20 c, 2 c, 2 c, 2 c, 2 c, 2 c, and output flag on the stack 3 (see the stack diagram on line 4\h 68i j k 14). 5 2 c, 2 c, 2 c, 2 c, 6 The assembly language 7\p 70q r s version is specific to the 68000 8 2 c, 2 c, 2 c, 2 c, and to fastForth. On line six, 9 the address of -ctype is 10 \ x 78 y z ( .., del loaded into address register 11 2 c, 2 c, 2 c, 20 c, 20 c, 40 c, zero. Line seven sees the re- 12 turn stack popped into ad- 13 dress register one. This leaves 14 the return stack containing the 15 address of the word which Scr # 1925 called the classifier daughter 0 \ ctype character classifier ( 21 5 93 CRC 18:07 ) word. It also leaves the ad- 1 \ Note the lack of range checking! dress of that daughter word's 2 \ Over 7f, you're on your own, tovarish! argument in ar1. The next 3 instruction reads the mask into 4 : classifier data register zero. 5 create c, \ does> >r dup -ctype + c@r> c@and ; ;s On line eight, the code 6 ;code -ctype *+ arO lea, \ addr of table copies the character to be 7 rp [+ arl mov, arl [ drO .b mov, \ mask to and 8 s [ drl mov, ( 7f # drl .wand, ) \ the character tested into data register one. A 9 0 arO 1 &D[ drO .b and, \ and the mask commented-out instruction 10 drO s -[ mov, \ results on the stack would provide some range 11 next ;c ;S checking, emulating the C 12 macro toasciio. The mask for 13 compile: mask --- \ compile a mask after the daughter word. the and is a 32-bit word value 14 run: c --- c fl \ return flag as to class of char. because only that portion of 15 the register is used as an in- dex. Scr # 1926 0 \ ctype character classifier ( 21 5 93 CRC 18:07 ) Line nine provides one in- 1 1 classifier isupper struction, anding the bit mask 2 2 classifier islower in dr 0 with the contents of the 3 \ 4 isn't used. lookup table. The source-ad- 4 8 classifier isdigit dressing mode is called "ad- 5 10 classifier isspace dress register indirect with in- 6 20 classifier ispunct dex." It adds the contents of 7 40 classifier iscntrl address register zero to the 8 \ 80 means printable but no other class word contents of data register 9 one, and a signextended byte 10 120r classifier isalpha 11 20 80 3 8 or or or classifier isprint displacement (here, zero) to 12 1 2 10 or or classifier isalnum produce the effective address 13 \ or roll your own.. . of the source. Assuming that 14 data register one contains a 15 value between zero and 7f,
(Continuer on page 38.) September 1993 October 8 Forth Dimensions UN*X Tools Used on the FSAT Pmject (or, "And Now For Something Completely Differentyy)Part I
Jim Schneider San Jose, California
At some point in the writing of a large project in Forth, the echo " /*********** end of $1 **********/" typical Forth programmer (if I am typical, and if there is such shift a thing as a typical Forth programmer) fires up a meta- or done cross-compiler to translate the work into a standalone application. This works fine as long as the programmer hasn't This is a trivial example, but I used this script several times done anything that is radically different from what the to download a small program from a remote UN'X site to my metacompiler writer had in mind. If the new project depends home box. More complicated scripts can automatically on new defining words, a different dctionary linkage configure and install sohare, perform periodic backups, structure, or a different way of handling code and data space, process huge text files and databases, or just about any other the metacompiler (at least those I've worked with) probably task. In fact, it is so useful that about the only reasons UWX won't be able to handle it without modifications. Addition- utilities are written in other languages is that the shell is ally, most metacompilers use the host dictionary to save quite expensive in terms of resources used versus results pro- a bit of state information, so a metacompiler can't be used for duced, and it doesn't manipulate binary files all that well. a huge project if the host dictionary is very limited. These are Because the shell is good for general purpose odd jobs, my two primary reasons for using the UN'X toolset to do but not for jobs that need to be done efficiently and much of the development for the project repeatedly, UN'X has a large assortment of utility programs. To ensure that everything I write about in this series of These can be broken down into categories in a variety of articles is understood, I'm going to describe several UN'X ways, but probably the most useful categories are (tradi- tools. My primary emphasis is going to be on the program- tional) programming tools, text manipulation utilities, and ming commands m4(1), yacc(l), and Ml), but I'm also miscellaneous. The traditional programming tools include things like compilers, linkers, library creation and mainte- nance utilities, source code control packages, and a peculiar The features discussed form a little utility to ensure programs are up to date. This "peculiar large enough subset to perform little utility" is called make. some useful work, I'm going to make functions by reading a file called (what else?) a make file. The make file contains lines that describe which use these features (and only files depend on other files (dependency lines), and lines to these) in later articles... tell make what to do if a file is out of date (i.e., a dependent is newer than something that depends on it, called a target). going to touch briefly upon sh(1) and make(1). For example, the following fragment of a make file: sh(l), the default command interpreter (or shell) on most £00.0: f0o.c f0o.h Makefile UN'X systems, allows you to write programs that take cc -c $(CFLAGS) $*.c advantage of the abilities of other programs. For example, this shell script (a script is a program to be interpreted by the tells make that if either foo.c, foo.h, or Makefile shell, like an MS-DOS batch file) will write the contents of the (usually the default name of the make file) were modified files specified on its command line to the standard output, more recently than foo . o,it is to perform a macro substitu- and provide a header and footer for each: tion on the second line and then execute it. make distin- # ! /bin/sh guishes dependency lines from command lines by the fact while [ -n "$1" ] that command lines start with one or more tab characters. do One point to remember about dependency lines: they may echo " /********** start of $1 **********/" contain any number of dependents, but only one target. cat $1 Thus, this would be invalid:
Forth Dimensions 9 September 1993 October £00.0 bar.0: f0o.c bar.c f0o.h Makefile newer file. In such a case, makewould pass the incorrect line: cc -c -0 -I./include Makefile An important feature of command lines is the fact that they can contain any valid UN'X commands. to sh to execute. Since Makef ile is not a C language file, cc Macro substitution is a form of text processing that will issue unfriendly diagnostics, and return an error code to substitutes any macro name references in the text by a muke. The reason this works in the built-in dependency rule previously defined substitution. There are two kinds of is that the .c in the rule tells make to substitute only the macros in make built-in (the $ * in the example) and explicit names of dependents that have an extension of .c. It will (the $ (CFLAGS)). The built-in macros are set by make to substitute these names (and only these names) into the line, stand for either targets or dependents of the last dependency regardless of which file is newer than the target. line it read. Without going into too much detail, the $ * in the If there is only one suffi on the target line of the built- example stands for foo, or the target without its extension. in dependency line, it is taken to be the extension of the Explicit macros are set in the make file, in the environment, dependent file, and the target is the dependent filename or are built into make. If make processed a line like this: without the suffi. For example, this: CFLAGS=-0 -I./include .C : cc $(CFLAGS) -0 $@ $< before it encountered the two lines in the example, the string £00: f0o.c $ (CFLAGS) would be transformed by macro substitution into -0 -I. /include. tells make that in order to build £00 from £00. c, it is to make executes a line by passing it to sh (hey, sh was perform macro substitution on the command line, and pass designed to execute command lines). Thus,the sequence of it to sh. The built-in macro $@stands for the current target file. events that make would follow when it encounters the Assuming that the macro CFLAGS is defined as above, the example above would be: line will be transformed into: 1. Check to see iff 00. o is out ofdate with respect to f00. c, cc -0 -I./include -0 £00 f0o.c foo.h,or Makefile 2. If £00. o is out of date, transform the line: (cc uses the option -0 to override the default name of its cc -c $ (CFLAGS) $*.c output file.) into: At this point, I should mention a caveat. The suffi rule cc -c -0 -I./include f0o.c in the built-in dependency must be "registered" by make. To and pass the transformed line to sh. cc(l1, the UN'X C register a suffix rule, it has to be added to the built-in macro compiler, uses the arguments -0 and -I . /include as .SUFFIX. For example, if you want to build .s files from .m options. They mean: perform optimization and search files, before you could put this: the path ./include for included files, respectively. .m. s: m4 $< > $@ Another feature of make is its ability to use built-in dependency rules. These rules tell make how to transform into a make file, you would probably need to put this: .SUFFIX=$ .SUFFIX) .m.s one file type to another without explicit rules. For example, ( the following two lines: .c.o: into the make file first. Usually, these suffi rules are built into SUFFIX: cc -C $ (CFLAGS) $< the macro . .c .sh .c.o .c.a .s.o .y.o .l.o .y.c .l.c tell make that whenever it finds a dependency line with a target with an extension of .o and a dependent file with an extension of .c that has a dependent file newer than the The UWXoperating systemuses the suffies .c, .sh, .o, corresponding target, it would have the second line of the .a, .s, .y, and .1 for C language source files, shell scripts, rule executed by sh, after macro substitution, in the absence object files, libraries, assembly langauge source files, yacc language source files, and lexlanguage source files, respec- of explicit commands. The macro $< stands for the depen- dents that are newer than the target in the dependency line. tively. Additionally, the suffi .h is used for C language .m i m4 This means that if make were to process this line: header files. I, myself, use the suffixes and . for £00.0: f0o.c f0o.h Makefile language source and include files, respectively. An additional feature of make is the possibility of having without any line following it, and any ofthe dependents were more than one command line for a given dependency line. newer than the target, make would pass this line to sh: For example, the pseudotarget clean is often used to "clean cc -c -0 -I./include f0o.c up" after a project is built. clean is called a pseudotarget because its commands don't actually create or update a file with the name clean.clean may have a dependency line The .c .o in the dependency line is called a suffix rule. and several command lines, like: The reason I used $ * .c instead of $< in the first example was clean : to handle the case where (for example) Ma kefi le was the rm -f * .o core a. out September 1993 October 10 Forth Dimension cd target1 ; rm -f *.o core a.out cd target2 ; rm -f *.o core a.out UN*X mivia For those of you who are curious, these are explanations In this deanhas no it is of the names of all the UN*X utilities mentioned in this considered to be "out of date." The three command lines in article (with the exception ofm4). this example would be passed to sh, which would execute the commands. The the second and third yacc-stands for "YetAnotherCompilerCompiler." When command lines contain two and the Unix system was young, almost everyone involved in m(l- to with a peculiarity WU2ke.As each line is the project was fascinated with advances in the field of generated, make passes it to a fresh invocation of sh. Since compiler theory. When this utility was installed, it was he each command line in a make file corresponds to a different fifth or sixth in the series of program that turn grammar shell, all commands that are built into sh (like cd in the descriptions into parsers. example) have no effect after the end of the line. Finally, a line starting with a # character is a comment. &- Stands for uLEXicalanalyzerm To get make to update a specific target, invoke mukewith that target as an argument. If make is invoked without sh- for wSHelln arguments, it checks the first target in the make file. For example, if this was the make file: muke - "makes" an update of a program .c.o: cc -c $< cat- "conCATenatesnthe contents of its arguments to the CFLAGS=-0 -I./include standard output OBJS=foo.o bar.0 baz.0 £00: $ (OBJS) cc - "C Compiler" cc $(CFLAGS) -0 $@ $(OBJS) £00.0: f0o.c fo0.h Makefile sed - "Stream EDitor" bar.0: bar.c f0o.h Makefile baz.0: baz.c Makefile grep - from the ed vernacular "g/RWpn which stands for clean : "global scan for regular expression and print resultn rm -f *.o core £00. ed- "line EDitor" the command: make baz .o awk- stands for its authors' initials: Aho, Wienberger, and Kernighan. awk is a powerful, stream-oriented, regular- would tell make to check baz . o, while this: expression-based programming language make By the way, I refer to Unix-like operating systems by would tell muke to check £00. "UWX' because: You now know more about make than I did when I There are several Unix and Unix-like operating started using it. In any make file associated with this project, systems available, and only two are actually named Unix. I will only use the features described above, and I will Since my primary development platform is a a PC done explicitly define all explicit macros. I will also explicitly with both XENIX and Linux (if I ever figure out how to define any built-in dependencies. make it stop fighting XENIX for the disk drives.. .), which There are several programming tools that also fall into the ,, Unix-like operating systems, I use the construct UWX text Indeed* many of the tasks we to refer to both of them. I may quire a Sun SPARCstation give to computers are in the realm of text manipulation; if we in the near future, which has yet flavor of Unix broaden our definition of text, they all are. UWX-like (SunOS, a very good port of 4.?BSD unix) operating systems have many utilities to make the job of 2. Unix was until recently a trademark owned by AT&T. custom text manipulation easier. The two main divisions of It is now oMed by Novell. Since no love for either the text processing category relate to how they do the lob. organization, I'm going to use a name that neither of them The first provides the ability to manipulate streams of text. owm, This is typified by this fragment: sed '/BEGIN/,/END/~'filex This is the documentation for filex which tells sed to read the file f ilex,and print all the lines (UN*X-type man page here) in the file, but delete (from the output only, not the original uuencOded image file!)allthelinesafterthefirstoccurrenceofthest.fing~~~~~ stuff (including the line it occurs on) up to the first following line END uuencoded image that contains the string END. So, if this was the contents of (more verbiage) filex: Forth Dimensions 11 September 1993 October the output would be: substitution, it's a good idea to quote the arguments to a This is the documentation for filex macro. m4 will consider a string of text that starts with a (UN*X-type man page here) backquote C) and ends with a single quote C) to be a single (more miscellaneous verbiage) word. m4 provides other macros besides define. One of the This is another trivial example, but it is useful for most useful is ifelse. T~ISmacro takes any number of processing, say, a file containing text, an encoded binary arguments, and if the first argument is equal to its second, the image, and then more text. result is its third. If its first argument doesn't match its second, The second division of text processing is macro process- and it has enough arguments, it tries to match its fourth and ing. make does this to generate lines to execute. The UN'X fifth, seventh and eighth, etc. If none of the pairs it checks operating system also provides a macro processor called m4. match, and the last argument is its fourth, seventh, etc., that (Don't ask me why-I could tell you why "sed'is named sed, is its result. If none of these cases work, the result is the null or even why "awF is named awk but I have no idea why string. "m4"is named m4.9 The syntax of m4 is very basic. Each All of this is much easier to do than to explain. For separate word in the input stream is matched against the example, thls: symbol table. If a match is found, the symbol is replaced by ifelse (cat,dog, ' cat equals dog', the string it stands for, and the process starts again at the 'cat does not equal dog1)# beginning of the substitution. If the word doesn't match a defined symbol, the word is copied to the output stream. would either print out cat equals dog, or cat does not (Note: because m4 operates literally, and the placement of equal dog, depending on whether the macros catand dog new lines is important, I will put a # character in the examples were defined to equal the same thing; and this: wherever a new line is supposed to be. So, even though a line ifelse (jim, is God, ' jirn is God today', may end at the end of a column in this article, if you are typing jim, is Devil, ' jim is Devil today', the examples into a computer, don't hit the enter key until ' jirn is mortal today') # you see the # character.) Thus, this fragment: define('jiml, 'is God') # would print one of three messages, depending on what I'd j im# defined myself to be. One more example: would print out ifelse ( jim, ,' jirn is nothing today', # fox, hound, ' the fox and the hound are is God# one') #
Notice the extra line in the output. This isbecause the new would print out jim is nothing today if j im were line at the end of the first line wasn't matched by a macro defined tobe the null string, or t he foxand thehound are name, so it was printed on the standard output. Indeed, the one if the macros foxand hound were equal, or nothing if new-line character can't match a macro name because m4 neither of the above were me. macro names consist of an upper- or lower-case letter or Since the macros define and ifelse take arguments, underscore followed by any number of letters, digits, or it would be reasonable to expect that other macros can use underscores. Anythlng else is either copied verbatim to the arguments as well. Implicitly, all macros have arguments, but standard output, or used as punctuation. Macros are defined if no arguments are given in the invocation, m4 fills the as shown in the example. The macro define (yes, it's a argument list of the macro with null strings. Since none of the macro, too) is called with two arguments. The first is the macros j im, cat, etc. use arguments, there is no difference name of the new macro, and the second is what the new (except typing and processor cycles) between: macro stands for. Also, notice the quotes around the name j im (this, is, an, argument, list)# and the substitution of the macro. I used them because m4 and: will do macro substitution of arguments to macros before the j im# arguments are passed to the macro. This means that if m4 were to encounter: Macros can use arguments, using the ubiquitous UN'X define ( jim, isn' t God) # convention of $1 to stand for the first argument, $2 for the second, all the way up to $9 for the ninth ($0 stands for the as the next line it were to process, it would perform macro mauo name, and $10 would be the first argument followed substitution on jim, and pass the arguments is God and by the character 0). The arguments must be enclosed in isn' t God to define. define would see that its first parentheses and separated by commas. The opening paren- argument doesn't look like a name, and either do nothlng or thesis that introduces the arguments must not be separated cause m4 to bail out. The net result would be printing another from the macro name. For example, if m4 were to process: newline(orexitingm4withanerrormessage).m4letsyou define('jim','ifelse($1,$2,'youpassed$O get around this by quoting. When m4is in macrosubstitution the same arguments ' ,' they differ' ) ' ) # phase and sees a string with quotes around it, it strips off the outermost set of quotes instead. Because quotes delay macro and if the next line was: September 1993 October 12 Forth Dimensior j im (FORTH, love) # The convention, described in the accompanying article, of using the '#' character to indicate hard new lines is applied in this source code. and FORTH was defined to be love, the result would be: masmmac.i you passed jim the dnl masmrnac .i# same arguments# define (' tab', ' ifelse (eval(len ($1)<$2) ,l, ' ) ) dnl# define ('masm-start ' ,' TITLE $1# If the you made the mistake .38 6p# of typing: divert ( 1)dnl# j im (FORTH, love) # EXTRN -next :NEAR,-doc01 :NEAR' 'declare (-next) declare (-docol) # divert (2)dnl# and FORTH was defined to be DATA SEGMENT USE32 BYTE PUBLIC# love, the output would end ASSUME ES : DATA# up being: -filename db len($l) ,"$1", 0# you passed jim the divert (3)dnl# same arguments DATA ENDS# ( love, love) # HEADS SEGMENT USE32 DWORD PUBLIC# ASSUMEFS : HEADS# (The latter example would divert (4)dnl# operate like this because m4 HEADS ENDS# will only process an argument STACK SEGMENT USE32 BYTE STACK# list as an argument list if the ASSUME SS : STACK# macro name is immediately divert (5) dnl# followed by an opening pa- STACK ENDS# renthesis. This is a result of the DICT SEGMENT USE32 BYTE PUBLIC# function that parses the input ASSUME CS: DICT, DS: DICT# stream. It can return any of divert (6)dnl# several values, and the value DICT ENDS# returned for a string that could END ' ) dnl# be a macro name differs from define ('declare', 'define (' $1-declared' ,1) ' ) dnl# the value that is returned for a define('namel, 'ifelse($2, ,$1,$2) l)dnl# string that could be a macro define ('qname', 'ifelse ($2, ,qt () $1. 'qt () -l# name followed by an opening define('qtl,")dnl# parenthesis.) define('qtll, 'define('qtl,") ')dnl# Some of the other usehl changequote (<, >) dnl# macros are pushdef (used define (
INTRAN is a simple, recursive, integer expression parser that Simple user interface permits formulas to be embedded in Forth words. The parser Ease of porting, maintenance, and extension directly represents the Backus-Naur statement of its grammar as Bulletproof error handling (recursive) Forth code. The resulting compiled code adds about 1Kb to the Forth kernel. And since this note is intended to illustrate general principles, I have striven to make INTRAN both clear and well In a letter to Forth Dimerrsiom (XIV/3), Peter Roeser documented. presented a wish list for Forths of the future. Some wishes We begin with the user interface: what we want INTRAN would require consensus from the Forth community, while to do. Primarily, we want INTRAN toembed infm expressions others (like the C interface) are already available. One wish- into word definitions. Just as HS/FORTH, e.g., allows assem- that Forth be broadened to encompass arithmetic expres- bler to coexist with high-level Forth through locutions like sions (including parentheses) 2 la Fortran, Pascal, BASIC, or : HI-LEVEL C-is withthe capacity of individual Forthniks (such as the words ... [%" assembler words " %I ...words ... author) to grant. This note presents an integer expression , translator-INTRAN-in a little over a kilobyte of code. we would like to insert formulae into words, with their translations compiled immediately as Forth. My scientific
To make porting, maintaining, formula translator uses F" ...I' as in and modiwing easier, I tried to : FORMULA (b+c) (c+d)" ; keep definitions dialect-invariant. F" a = / to do precisely this. The notation has proven so convenient INTRAN came about because I needed to translate integer and transparent that I chose a similar one for INTRAN. If we expressions appearing as indices in Fortran DO loops. That define a word is, Fortran permits the construction : EXPRl DO 100 I=(J-K) /2, (J+K)/2+M, K/4 i" (I+J)/2 + K" ; ... stuff... 100 CONTINUE (I+J)/2 + K should be translated and compiled. When we decompile EXPR1-in HSRORTH, e.g., using the word The formula translator described in my book Scientific SHOW-we will see Forth: a Modern Language for ScientiJic Computing (avail- SHOW EXPRl IJ+2/ K+ ; ok. able from the Forth Interest Group) parses mixed (single- and double-precision, real and complex) floating-point expres- Experience shows the value of dry runs: during testing we sions. Unfortunately, for technical reasons (having to do with might want INTRAN to translate interactively, without com- how I implemented operator overloading) the formula piling. That is, when we type translator was unsuited to simple integer expressions. This i" (I+J)/2+Kn implied a distinct parser for integer expressions. The one I wrote compiles to 702 bytes and surely could be squeezed INTRAN should send the Forth translation further. Terseness, however, subverts clarity, so here I IJ+2/ K+ ok present a lengthier but more pedagogical version. Since INTRAN is intended to be production-quality code, to the screen. To make all these things happen, i" must be we must address the following programming issues: state-smart. These abilities alone would make INTRAN the
September 1993 October 16 Forth Dimensions HARVARD SOFTWORKS NUMBER ONE IN FORTH INNOVATION (513) 748-0390 P.O. Box 69, Springboro, OH 45066 You already know HS/FORTH gives more speed, HWFORTH runs under MSDOS or PCDOS, or from ROM. Each level includes power, flexibility and functionality than any other all features of lower ones. Level upgrades: $26. plus price difference between levels. implementation. After all, the majority of the past Source code is in ordinary ASCII text files. several years of articles in Forth Dimensions has been on HS/FORTH supports megabyte and larger features first developed in HS/FORTH, and many major programs & data, and runs as fast as 64k limited Forths, even without automatic applications discussed had to be converted to HS/FORTH optimization -- which accelerates to near after their original dialects ran out of steam. Even assembler language speed. Optimizer, assembler, and tools can load transiently. public domain versions are adopting HS/FORTH like Resize segments, redefine words, eliminate headers without recompiling. Compile 79 architectures. Isn't it time you tapped into the source as and 83 Standard plus F83 programs. well? Why wait for second hand versions when the PERSONAL LEVEL $299. original inspiration is more complete and available NEW! Fast direct to video memory text & scaled/clipped/windowedgraphics in bit sooner. blit windows, mono, cga, ega, vga, all ellipsoids, splines, bezier curves, arcs, turtles; lightning fast pattern drawing Of course, what you really want to hear about is even with irregular boundaries; powerful parsing, formatting, file and device YO; our SUMRlER SALE! Thru August 31 only, you can DOS shells; interrupt handlers; dive into Professional Level for $249. or Production Level call high level Forth from interrupts; single step trace, decompiler; music; for only $299. Also, for each utility purchased, you may compile 40,000 lines per minute, stacks; file search paths; format to strings. select one of equal or lesser cost free. software floating point, trig, transcen- dental, 18 digit integer & scaled integer math; vars: A B * IS C compiles to 4 Naturally, these versions include some recent words, 1..4 dimension var arrays; improvements. Now you can run lots of copies of automatic optimizer delivers machine code speed. HSIFORTH from Microsoft Windows in text andlor PROFESSIONAL LEVEL $399. graphics windows with various icons and pif files hardware floating point - data structures available for each. Talk about THE tool for hacking for all data types from simple thru complex 4D var arrays - operations Windows! But, face it, what I really like is cranking up complete thru complex hyperbolics; the font size so I can still see the characters no matter turnkey, seal; interactive dynamic linker for foreign subroutine libraries; round how late it is. Now that's useful. Of course, you can run robin & interrupt driven multitaskers; dynamic string manager; file blocks, bigger, faster programs under DOS just as before. sector mapped blocks; x86&7 assemblers. Actually, there is no limit to program size in either case PRODUCTION LEVEL $499. since large programs simply grow into additional Metacompiler: DOS/ROM/direct/indirect; segments or even out onto disk. threaded systems start at 200 bytes, Forth cores from 2 kbytes; C data structures & stmct+ compiler; MetaGraphics Turbowindow-C library, Good news, we've redone our DOCUMENTATION! 200 graphidwindow functions, Postscript The big new fonts look really nice and the reorganization, style line attributes & fonts, viewports. along with some much improved explanations, makes all ONLINE GLOSSARY s 48. that functionality so much easier to find. Thanks to PROFESSIONAL and PRODUCTION excellent documentation, all this awesome power is now LEVEL EXTENSIONS: FOOPS+ with multiple inheritance $ 79. relatively easy to learn and to use. TOOLS & TOYS DISK $79. 286FORTH or 386FORTH $299. 16 Megabyte physical address space or And the Tools & Toys disk includes a complete ,gab* vihual for ,,, and data; mouse interface and very flexible menu support in both ~~~~~~~~p~~;~~~,""$t~~,"~ble; text and graphics modes. Update to Revision 5.0, ROMULUS HS/FORTH from ROM $99. including new documentation, from all 4.xx revisions is Shippind8ystem: US: 19. Canada: $21. $99. and from older systems, $149. The Tools&Toys foreisll: $49. we a.ceptMC, VISA, & AmEx update is $15. (shipping $5.US, $lO.Canada, $22.foreign) Figure One. Rules for INTRAN's grammar. To make porting, maintain-
In an assignment like B=(I+J)/2+K we need to know what ASCII + ASCII - a l b + I - B refers to. A VARIABLE is stored to by the phrase B ! while ASCII * ASCII / a l b * I / a VAR uses the locution IS B. Although good programming ASCII = ASCII = a l b = I = practice frowns on it, we can even modify CONSTANTSwith the phrase ' B ! . Since the latter phrase works equally well At run time, the words + I -, * 1 /, and = I = compare the for CONSTANTS,VARIABLES, and VARs, it solves our prob- TOS (top of stack) with two built-in numbers; if either lem and requires no decisions (only in HS/FORTH-will not matches, the words return (-1). The plan is to write a work in other Forths). generic character-finding routine that will search a string byte Finally, we want the parser to report bad input, and to by byte, and with each byte EXECUTE one of the above ignore white space inserted for readability. With these words. That is, the search word will take as input the location provisos, we have completely specified the user interface. of the string and the CFA (code-field address) of the word September 1993 October 18 Forth Dimensions 1 Figure Two. INTRAN's BNF grammar expressed as psuedo-Forth. I
:
Forth Dimensions 19 September 1993 October Some sort of stack is manifestly demanded by recursion. are no more arguments"; whereas recursion implicitly keeps Eventually I realized a string stack was excessive: since each track of execution. To guarantee this with a multiply fragment appears once and only once, it is enough to store recursive algorithm such as INTRAN, we must ensure, first, pointers marking the beginning and end of each fragment, that each parsing word takes the same number of arguments; rather than copying the fragments themselves. We still need and second, that each leaves nothing on the stack. Thus, to a stack to pass the arguments during recursive calls, however, make a recursive call to
: skip ( endbeg char cia -- endbeg' ) D>R 1- BEGIN 1+ DDUP = OVER C@ DR@ EXECUTE OR UNTIL DRDROP ;
: -BL ( end beg -- end' beg) \ strip blanks out of a string UNDER - 1+ -TRAILING \ strip trailing blanks OVER + 1- SWAP ( end" beg) DUP>R BEGIN BL CFA' = skip \ -> 1st BL DDUP ( end adr end adr) BL CFA' <> skip \ -> non-blank PLUCK ( end adr adr+n-1) DDUP < \ not at the end yet
WHILE OVER DDUP -. ( end adr src dst #bl) -ROT D>R -ROT ( #bl $end adr) DDUP - 1+ DR> ROT CMOVE ( #bl $end adr) -ROT SWAP - SWAP REPEAT DDROP R> ;
/ Figure Four. Moving the pointers. I : -bl- ( beg end .op -- beg' end' .op) >R 1+ BEGIN 1- DUPC@ BL <> UNTIL \ skip leading SWAP 1- BEGIN 1+ DUPC@ BL <> UNTIL \ skip trailing SWAP R> ;
efficient as my "afterthought" method (when I realized since this obviates multiple tests of the parenthesis level blanks should be allowed). Whereas the preceding code during execution. adds 135bytes, the "afterthoughtnadds 57. How does it work? Having tested the word il'on many different cases and We decompose as though the blanks were not present. The having tried (unsuccessfully, one hopes!) to make it fail, we substring pointers point to the ends of (sub)strings with are now ready to try out the most dangerous part of the (possibly) leading and trailing blanks. It is much easier to development: granting i" the power to compile expres- advance the beginning pointer rightward past the leading sions. Many Forths (and the new ANS standard) include a blanks and the end pointer leftward past the trailing ones, wordlike EVAL that will compile directly from astring. If your than to actually compose a new, blankless string from one Forth can do this, all that is needed is to redirect the output with blanks sprinkled through it. So we compose a word that from the screen to a buffer, convert that to a counted string, moves the pointers as noted (see Figure Four), and then and EVALuate the string. HSEORTH has an equivalent form apply it whenever a new substring has been dissected out of redirection, namely the ability to load from a buffer (the and its pointers placed on the stack. The definition -bl- (the text in the buffer mustbe terminated by double4). The (non- name suggests that blanks are removed at both ends) standard) word that does this is MLOAD which expects a requires 47 bytes (in an indirect-threaded system), and the segment descriptor and offset on the stack. The definitions five subsequent references to it add another ten bytes. needed to implement expression compilation are then as We are nearing the end of the exposition. The final shown in Figure Five [on nextpagel.The only major changes definition (the initial one, were we so foolish as to design top- from the non-compiling version of i" are the state-&pen- down) is i". Before we add the compiling abilities described dent IF...ELSE.. .THEN and making i" IMMEDIATE, so it above, we only require that it acquire the text, place pointers can do its work within a word being defined. to the ends of the string, as well as a denothing operator token, on the stack, and invoke the first parsing word,
. i" ASCII " TEXT o-ok \ check for balanced parens PAD adr>ends BL CR
OK 17:27:16 3/2/1993 JulianV. Noble is a professor of physicsat the Universityofvirginia and theauthor of Scientific Forth. Heearned his B.S.atCalTechin 1962andhis Ph.0.at Princeton We check for balanced parentheses before starting to parse, in 1966, and once designed a floating-point co-processor for the Jupiter Ace.
Forth Dimensions 2 1 Se~ternber1993 October Figure Five. Implementing expression compilation. 1
256 SEGMENT intran \ make a named segment to hold output from i" "
: iV->MEM intran @ 0 256 0 FILLL \ initialize buffer intran OPEN-MEM >MEM ; \ output -> buffer
: MEM-> intran @ 0 MLOAD \ load from intran CLOSE-MEM ;
. i" ASCII " TEXT 0-0k \ input, check () PAD adr>ends BL CR \ set stack STATE @ \ compiling? IF ivv->MEM \ vector to intran
INTRAN code listing.
\ Mini expression parser \ version of 11:50:06 3/6/1993 \ compiles to 1239 + 256 bytes TASK INTRAN
\ This program was written to be used with HS/FORTH, an indirect- \ threaded FORTH for the PC. It contains several non-standard words \ and usages (especially not ANS !) but has been designed to be easy \ to translate to your own dialect.
: a lb ( cl ~2 --) CREATE Dl DOES> D@ ROT UNDER = -ROT = OR ; ( c -- f) \ Defining word. Child words contain 2 built-in characters. \ Test char on stack and return true if it is either built-in char \ OK 20:31:59 3/1/1993
ASCII + ASCII - alb +I- ASCII * ASCII / alb *I/ \ OK 22:10:12 3/1/1993 / VARIABLE Olevel 0 ()level ! \ holds current parens level I : inc ( ) c -- ASCII) OVER = SWAP ASCII (= - ()level +! ; \ increment/decrement Olevel; ( increments, ) decrements. \ OK 20:44:29 3/1/1993
: adr>ends ( Sadr -- beg end) COUNT OVER + 1- ; \ convert address of counted string to pointers to beg and end of text \ OK 20:34:18 3/1/1993
: find2 ( beg end cfa -- adrlO ) ()level O! DUP>R \ initialize -ROT DO I C@ DUP inc() \ adjust 0 level OVER EXECUTE (--cfaf) \ test input () level @ O= \ exposed?
September 1993 October 22 Forth Dimensions AND \ found? IF DROP I LEAVE THEN ( -- adr) -1 +LOOP R> OVER <> AND ; \ (adrlO) \ search text from beg to end and test using routine pointed to by cfa \ leave character-address if found, 0 otherwise. \ OK 22:03:34 3/1/1993
: print ( beg end .op -- ) -ROT \ move op token DUP C@ >R \ save last char on rstack OVER - TYPE \ type all but last char R> DUP ASCII @ = \ last char = @ ? IF SPACE THEN \ emit space EMIT SPACE \ type last char SPACE EMIT SPACE ; \ type operator \ print out the string and operator on the stack \ OK 15:17:49 3/2/1993
: WITHIN ( k m n --f) ROT UNDER MIN -ROT MAX = ; \ return "true" if n >= k >= m, else "falsew \ Note : UNDER is TUCK in ANS \ OK 21:44:15 3/2/1993
: digit? (c-- f) ASCII 0 ASCII 9 WITHIN ; : letter? ( c -- f) 32 OR ASCII a ASCII z WITHIN ;
:
: <#> ( beg end -- f) \ <#> -> {digit}+ 1+ SWAP ( end+l beg) -1 -ROT ( -1 end+l beg) DO I C@ digit? AND LOOP ; \ OK 12:55:49 3/2/1993
: simple? ( beg end -- f) DDUP <#> -ROT
VARIABLE BLBL 8224 BLBL ! \ "blank blankw : NULL BLBL DUP 1+ ; ( -- beg end)
\ set up forward reference for
: (
Forth Dimensions 23 September 1993 October :
\ auxiliary words for
: 3SWAP (abcdef--defabc) 6 ROLL 6 ROLL 6 ROLL ; \ Note: in F83 and ANS it would be 5 ROLL
: rearrange ( beg end adr .op -- adr+l end .opt beg adr-1 .op ) >R DUP>R ( -- beg end adr) 1+ SWAP ROT R@ C@ ( -- adr+l end beg .opt ) SWAP R> 1- R> ; \ OK 17:05:24 3/2/1993
:
:
CFA'
: put0 ( beg end -- beg end+l) DUP>R OVER - 1+ >R DUP DUP 1+ R>
I I September 1993 October 24 Forth Dimensions : fix- ( beg end -- beg end £1 \ leading "-" -> leading "0-" OVER C@ ASCII - = \ leading - ? IF put0 THEN ; \ OK 11:43:23 3/3/1993
ASCII = DUP alb =I= \ to find =
:
>R NULL ASCII ' ( -- beg adr-1 "!" beg' end' "I") R> R> 1t SWAP ( -- adr+l end) R> -bl- >R \ eliminate spaces fix- \ 11-11 -> "0-" R>
: 0-ok? Olevel O! PAD COUNT OVER + SWAP DO I C@ inc () LOOP () level @ IF CRT ." Unbalanced parentheses!" ABORT THEN ; \ OK 17:52:30 3/2/1993
\ : is' ASCII TEXT 0-ok? \ PAD adr>ends BL CR
256 SEGMENT intran \ make a segment to hold output from i" "
: ill->MEM intran @ 0 256 0 FILLL \ initialize buffer intran OPEN-MEM >MEM ; \ output -> buffer
: MEM-> intran @ 0 MLOAD \ load from intran CLOSE-MEM ;
. i" ASCII " TEXT ( ) -ok? \ balanced 0 ? PAD adr>ends BL CR \ set initial stack STATE @ \ compiling? IF iW->MEM \ vector to intran
Forth Dimensions 25 September 1993 October FORTHTUTORIAL, LESSON #6 Terminal Input and Output C.H. Ting San Mateo, California rowork through this tutorial, you will need the random-number added to the output string. generator presented in the last issue's lesson.] #S (d-00) Format Output Numbers Convert all significant digits and add them to the output We have discussed a few of the Forth instructions which string. print numbers to the screen. Here is a list of these instructions: # > ( d - addr n ) (n-1 Terminate the number string, and leave addr and the count Print signed n followed by a space. of the string's length for TYPE. u. (u-1 HOLD ( char -- ) Print unsigned u followed by a space. Add an ASCII character to the output string.
D. (d - ) SIGN (n-> Print signed double integer d with a space. Add a - sign to output string if n .R (nl n2-) BASE ( -- addr ) Print nl in n2-column format. Memory address containing current radix. These instructions are sufficient for most applications in DECIMAL ( -- which numbers are displayed on the screen to tell a Set rador to 10 for decimal conversion. programmer to know what's going on in the computer. But to display numbers to the end user, they have to be formatted The radix number which controls the number conversion in specific ways not covered by the above list of commends. can be changed at will. This flexibility allows the Forth user Forth provides component instructions that enable you to to do very interesting and powerful number formatting. format numbers in any desirable fashion. We will discuss these instructions and use a few examples to illustrate how Telephone Numbers they are used to create custom number formats. Telephone numbers, including the area code and even an The formatting process starts with a double integer on the international dialing code, can be comfortably represented top of the stack. The output is a formatted string in the free by double integers. To print a telephone number with the memory below the text buffer pointed to by the instruction custom format, we define the word Phone as in Figure One. PAD. The output string is constructed backwards, one digit A double integer can be entered from the keyboard by at a time. Whlle constructing the string, any ASCII characters including a period anywhere in the input number string. To can be inserted into the string to improve readability. The print the phone number shown in the comment in Figure building blocks for number formatting are the following: One, type: 415432.1230 Phone < # ( -- Start the number-formatting process. and the properly formatted string will be printed on screen. # ( dl -- d2 ) Time of Day Divide dl by the radix number. The quotient is left on the Assume that the time of day is represented by an double stack as d2. The remainder is converted to a digit, which is integer counting 1/100ths of a second since midnight. The September 1993 October 26 Forth Dimensions output format specification is HH:MM:SS.XX, where XX be defined as in Figure Three. represents hundredths of a second. (See the code presented in Figure Two.) Radix for Number Conversions Between midnight and noon, there are 4,320,000 hun- By changing the radix stored in BASE, the Forth user can dredths of seconds. If we type: freely convert numbers from one base to another, according 4320000. TIME to the needs of the moment. Programmers must often convert numbers from decimal to hexadecimal, octal, and binary, and we should see 12:00:00.00 printed. Do verifjr it. vice versa. The number conversions can be done simply by changing the radix with the following instructions: Angles For navigational purposes, global positions are repre- DECIMAL sented in angles of latitude and longitude, in the form of : OCTAL 8 BASE ! ; DDD:MMtSS". (Here we are using : for degrees because we : HEX 16 BASE ! ; don't have the proper character for degrees.) This format is : BINARY 2 BASE ! ; only slightly differrent from the above time format, and can : RADIX36 36 BASE ! ; : RADIX19 19 BASE ! ; Special radix bases are Figure One. Telephone numbers. , sometimes very useful for par- ticular situations. For example : Phone ( d -- , print the telephone number in [415] 432-1230 format ) ra&x 36 is very convenient < # ( start output string ) when compressing alphanu- # # # # ( convert the last 4 digits ) merical string to fit into tight 45 HOLD ( insert - sign ) memory spaces, because it # # # ( convert the next 3 digits ) encompasses the ten numeri- 32 HOLD ( add a space ) cal digits and the 26 characters 41 HOLD ( add right parenthesis ) of the alphabet. My favorite # # # ( add area code ) radix is 19, which is useful in 40 HOLD ( add left parentheses ) encodng board locations in #> ( done formatting ) the Chinese (or Japanese) game TYPE SPACE ( print the output string ) of Go. Try converting numbers among different radices: Figure TWO. The time of day. I DECIMAL 12345 HEX . : Sextal ( -- ) 6 BASE ! ( set radix to 6 ) HEX ABCD DECIMAL U. : :SS ( dl -- d2 , divide dl by 60 and add the remaider as 2 digits ) DECIMAL ( to the output string ) 100 BINARY . # ( convert 1 digit in decimal ) Sextal # ( convert next digit in sextal ) BINARY DECIMAL ( restore readix to decimal ) 101O101O1O1O DECIMAL . 58 HOLD ( add : to output string ) Real programmers impress novices by carrying a H-P cal- : Time ( d -- ) culatorwhich can convennum- < # ( start output string ) bers between decimal and # # ( convert hundredth of second ) hexadecimal. A Forth computer 46 HOLD ( add . has this calculator built in, be- :SS ( convert seconds ) sides other functions. :SS ( convert minutes ) #S ( convert hours ) Message Coding # > ( terminate conversion ) After you have entered the TYPE SPACE ( print results ) code from the preceding sec- tion, try this: Forth Dimensions 27 September 1993 October Figure Three. The degrees, minutes, and seconds of angles. RADIX36 : Message : Angle ( d -- , print angle in the DDD:MM'SSW format ) THE. WOLVES. ARE. < # ( start output string ) COMING. ; 34 HOLD ( add " for seconds ) DECIMAL # ( decimal digit for second ) Sextal # DECIMAL ( sextal digit for second ) Try the following and you 39 HOLD ( add ' for minutes ) will see how the message is :SS ( convert minutes ) coded and decoded: #S ( convert degrees ) RADIX36 # > ( done formatting ) Message D. D. D. D. TYPE SPACE ( print ) , DECIMAL Message D. D. D. D. Please note that the words Figure Four. Printing the PC's character set. 1 in Message are appended with periods to force them to : Printable ( n -- n , convert non-printable characters to spaces ) be converted to double inte- DUP 14 < ( 7-13 are special formatting ) gers in radix 36. By the way, IF DUP 6 > ( characters not displayable ) the largest number represent- IF DROP 32 THEN ( substitute a space ) able in radix 36 is 1214123. It THEN is, therefore, possible to rep resent any six-character alpha- numeric string as a double : HorizontalASCIItable ( -- ) integer in radix 36. CR CR CR 5 SPACES Terminal Input and 16 0 DO I 4 .R LOOP ( show sequential column header ) output CR The Forth user interacts 16 0 DO ( do 16 rows ) with Forth through the terrni- CR I 16 * 5 .R ( print row header ) nal: a keyboard to enter num- 16 0 DO ( print 16 characters in a row ) bers and instructions, and a 3 SPACES screen to display results and J16*I+ ( current character value ) other information. The most Printable elementary Forth instructions EMIT ( print it ) controlling the terminal I/O LOOP ( loop for next character ) are: LOOP ( loop for next row ) CR KEY ( -- char ) Accept a keystroke from the keyboard and return the cor- : VerticalASCIItable( -- ) responding ASCII code. CR CR CR 5 SPACES KEY? (--f> 16 0 DO I 16 * 4 .R LOOP ( show column headers ) Return a true flag if a key was CR pressed. 16 0 DO ( do 16 rows ) CR I 5 .R ( print row header ) EMIT ( char -- ) 256 0 DO ( do 16 columns ) Display the character whose 3 SPACES ASCII code is on the top of JIt ( current character ) stack. Printable EMIT 16 +LOOP ( skip 15 characters between columns) TYPE ( addr n -- ) LOOP Display a string n characters CR long from memory location addr. I September 1993 October 28 Forth Dimensions Figure Five. The love letter. / 1 VARIABLE NAME 12 ALLOT VARIABLE EYES 10 ALLOT VARIABLE ME 12 ALLOT : ENTER ( addr n -- , accept a string up to n characters to the ) ( memory area starting at addr .) 2DUP BLANK ( clear the memory area to spaces ) Type EXPECT ( wait for a string up to n ) HorizontalASCIItable ( characters or a return ) or VerticalASCIItable : VITALS ( -- , get and store the names and the eye color in arrays ) CR ." Enter your name: " to display the complete IBM ME 14 ENTER ( get your name ) PC character set in two differ- CR ." Enter her name: " ent forms. Many of the graphic NAME 14 ENTER ( get her name ) characters are interesting be- CR ." Enter her eye color: " cause they allow the user to EYES 12 ENTER ( get her eye color ) draw fairly nice forms on the screen for business applica- tions. These instructions are : LETTER ( -- ) also handy if YOU want to use CR CR CR CR the graphic characters to con- . " Dear " struction unique screen dis- NAME 14 -TRAILING TYPE play~. . I' ," CR ." I go to heaven whenever I see your deep " A Love Letter EYES 12 -TRAILING TYPE Figure Five presents a very ." eyes. Can " CR interesting example adapted .'I you go to the movies Friday?" from Leo Brodie's Starting CR 30 SPACES Forth. The program allows you . " Love, " to print a love letter inviting CR 30 SPACES your girl friend to see a movie. ME 14 -TRAILING TYPE CR After entering the code, type ." P . S . Wear something " VITALS and enter all the infor- EYES 12 -TRAILING TYPE mation requested; then type ." to show off those eyes! " LETTER. You will see the very CR CR CR moving letter. , In this example, we also introduce several important Forth instructions dealing with strings and memory: EXPECT ( addr n -- ) Accept n characters from the keyboard and store them at ALLOT (n--) memory location addr. If the string is terminated by a return, Allocate n bytes of memory following a variable, creating an the number of characters accepted is stored in the variable array to store a string of characters. SPAN. FILL ( addr n char -- ) ASCII Character Table Fill a memory array, n bytes long from memory addr, with the In most computers, characters, numerals, and punctua- character char. tion are represented in eight-bit bytes. The American Stan- dard Characters for Information Interchange (ASCII) use byte -TRAILING ( a nl -- a n2 ) values from 32 to 127 to represent printable symbols. These Modifiy string length nl to exclude trailing spaces. symbols can be printed on the terminal screen and on any standard printers. Outside of this range, symbols are repre- Notice that the suing arrays ME,NAME, and EYES must be sented differently by different computers. The IBM PC cleared to spaces before calling EXPECT in order to enter displays graphic symbols when byte values outside the new information, because we don't know how many above range are sent to the screen. The code in Figure Four characters will be entered into these arrays. After the allows you to display the regular character set, with the information is entered, the strings can be retrieved using graphic characters, in a nicely formaued table. -TRAILING to strip off the trailing spaces. Forth Dimensions 29 September 1993 October / Figure six-a. HOW CONVERT works. 1 Number Input CONVERT ( dl addrl -- d2 addr2) On many occasions, it is Convert the string at addrl to a double integer and add it to dl. necesary to ask the user to Leave the sum as d2 on the stack; addr2 points to the first non-digit type a number as a string. in the string. After the string is accepted, we An example of how to ask the user for a number: have to convert it into a num- / and push it On the data : GetNumber ( -- ) stack for subsequent instruc- CR . Enter a Number: ,, ( show message ) tions t~ use. The primitive PAD 20 ENTER ( get a string ) instruction to convert a nu- 0 0 PAD 1 - CONVERT ( convert string to a double ) meric string to a binary num- ZDROP ( leave a single integer on stack ) ber is CONVERT-see Figure ; Six-a. With this useful instruc- tion, we can write the game a shown in Figure Six-b. Number-guessing game. ] Figure Six-b. Type GUESS to the game, and the : InitialNumber ( -- n , set up a number for the player to guess ) computer will entertain a user CR CR CR . mat limit do you want ?" for a while. Note theuse of the GetNumber ( ask the user to enter a number ) loop structure: CR ." I have a number between 0 and " DUP . BEGIN CR ." Now you try to guess what it is." You can jump out of the : Check ( nl -- , allow player to guess, exit when the guess is correct loop by typing the instruction BEGIN CR . " Please enter your guess." EXIT, which skips all the in- GetNumber structions in a ~oithdefinition 2DUP = ( equal? ) up to ; (the semicolon& IF 2DROP ( discard both numbers ) thus terminating execution of CR ." Correct!!!" the current definition and con- EXIT tinuing to the next definition. THEN OVER > IF CR ." Too High!" ELSE CR ." Too low." THEN CR 0 UNTIL ( always repeat ) : Greet ( -- ) CR CR CR ." GUESS A NUMBER" CR ." This is a number guessing game. I'll think" CR ." of a number between 0 and any limit you want." CR . " (It should be smaller than 32000.) " CR ." Then you have to guess what it is." : Guess ( -- , the game ) Greet BEGIN InitialNumber ( set initial number) Check ( let player guess ) CR CR ." Do you want to play again? (Y/N) " KEY ( get one key ) 32 OR 110 = ( exit if it is N or n ) UNTIL Dr. C.H. Ting is a noted Forth authority CR CR ." Thank you. Have a good day." ( sign off ) who has made many significant conlri- CR butions to Forlh and the Forth Interest Group. His tutorial series will continue in succeeding issues of Forth Dimensions. September 1993 October 30 Forth Dimensions I A Forum for Exploring Forth Issues and Promoting Forth The Point of No Return Mike Elola San Jose, California Most professional programmers have abandoned inter- interpret the low-level instructions generated by most com- preted languages in favor of languages with highly evolved pilers.) compiling systems. Forth's compiling tools remain simple by Major benefits are associated with compiled applications. comparison. One of them is speed. Another benefit is that the form that The ability to merge independently compiled code has the executable file takes is not source code. While a different been a widely appreciated strategy employed by these executable file is required for each different hardware compiled languages. The term used to describe the strategy instruction set, this has not proved to be a liability. There are is separate compilation. Function libraries are a trivial many compiler vendors helping to ensure that you can write extension of that particular strategy for developing applica- a program in the compiled language of your choice and still tions. produce executable files to suit your choice of computer Interpreters usually do not compare favorably to compil- hardware. ers, because they perform a translation step at each run of the program. Besides the ensuing performance problems, there Divide and Conquer are other perceived problems for interpreters. For example, Separate compilation is the feature of modern compiling source code is considered a troublesome format in which to systems that supports the partitioning of programs during distribute applications. development. It allows each subdivision of a program to be The key virtue of an interpreted language is the hardware independently refined. independence it accords to source code. Independence from Each translated subdivision is stored in a form that is operating systems, processing units, and particular periph- neither a source format nor an executable format. Separate era1 devices are possible benefits. A "standard" interpreter compilation introduces a new file format that is suitable for that runs on microprocessors inside a wealth of devices processing by a link editor, or "linker."The linker can process creates a standard way of controlling those devices. It also the translated subdivisions of a program to create an accords the source code a considerable level of transportabil- executable file. I am calling the format of the intermediate ity between the devices. The most favorable conditions for files produced by such compilers a "linker-ready" file format. transportability occur when one company controls the See Figure One for an illustration of the processing involved. language definition. Adobe is the company in control of Each linker-ready file contains routines that can be PostScript, an interpreted pagedescription language. thought of as services, particularly if the corresponding A PostScript description of a printed page always causes subdivision of the program is stable. The clients for those the same page to be printed. The page is printed faithfully, services are any other subdvisions of the program that need regardless of the computer platform sending the job, and to use the services. It's possible for the service and client roles regardless of the type of PostScript device receiving the job- of various subdivisions to alternate over time, but a thought- although quality and print resolution may vary. The PostScript ful design should eliminate the need to do so. language improves the transportability of printers, helps Once translated to a linker-ready format, the stable simplify device drivers and other applications on the host subdivisions of the program need only be processed by the computer, and helps make families of devices more compat- linker. The remaining source code is changed and recompiled ible, including printers, typesetters, and plotters. until it is processed without error. (The interfaces between the service and client routines must not be violated as To avoid re-translation of source code each time a changes are made.) Then the linker can create a new version program is run, compilers capture the translated source code of the whole program for testing. into a new file. The new file is the executable file. Besides The advantage of a type-checking compiler is that it can 1 running faster, such an executable file runs with less certify that the interfaces to precompiled routines are strictly 1 supporting software. meprocessing hardware suffices to followed. Although the service routines are not repeatedly Forth Dimensions 3 1 Se~tember1993 October recompiled, a type-checking compiler normally processes a piecemeal, and the ease-of-use of basic compilers and source language description of the interface to each interpreters has been abandoned. precompiled function. The interpretation strategy uses just one file containing The header file should contain the names of each of the code that serves all the required purposes. The source code precompiled routines, any parameters they use, and the data for an application and the executable file are the same file. types of those parameters. A header file usually resides close Progressing to a compilation strategy, two files must be to the source code file that actually defines the routines. maintained: (1) a source code file; and (2) an executable file. Sometimes you may have no other source code but the Progressing from all-at-once compilation to separate header file, such as when you use a library for which source compilation, three types of files must be maintained: (1) code is not included. several source code files; (2) several linker-ready files The compiler's processing of these interface descriptions produced by compilers or assemblers; and O an executable does not generate code for the linker-ready file, nor for any file produced by a linker. other file. The interface description files exist merely so the (To anticipate future trends, consider this scenario: To compiler can detect misuses of the interfaces to the progress from separate compilation with all-at-once linking precompiled functions inside existing linker-ready files. to separate compilation and dynamic linking, no additional (To change a function's interface, several source language files are necessary at compile time. However, the main files must be brought into agreement: the source file for the executable file may later require the linking of it and service function, the source file for the interface description, accompanying linker-ready files. Therefore, the end-user and all the source files containing client functions. Then any computing platform must be equipped with suitable "link- linker-ready files that were based upon the old interface must ing" software and linker-ready files to successfully run be deleted and regenerated. Finally, the executable file can programs that take advantage of this feature.) be rebuilt.) The maintenance of many files is the price paid for the Because of this layered approach to the creation of an improved ability to partition programs. Nevertheless, such executable file, the linker never needs to process the syntax partitioning helps support greater code reuse as well as or grammar of any high-level language (nor any assembly parallel development by several programmers. The efi- mnemonics). For each processor family, associated compil- ciency gained from these practices is often a critical factor ers transform source code in various languages into roughly contributing to the success of a project. Very small program- equivalent types of linker-ready files. ming projects may be the only cases where separate compi- Because it works with previously translated code, the lation hinders more than it helps. linker lends support for development using a mix of high- and low-level programming languages. Accordingly, assem- Taking Up Collections blers often rely on subsequent linker processing to generate The modern compiler consists of two or more layers of executable files. tools, as well as collections of files maintained by you or by Some of the problems you confront for mixed language various build processes (see Figure One). development are also problems for same-language develop- The raw material for building an application is a pool of ment through the auspices of separate compilation. For files that you bring together. One or more files in the pool example, the size of integers passed between service func- may already be in a linker-ready format. Perhaps one file was tions and their clients must be the same. Because PC-based reused from another project. Perhaps no changes will be applications can be compiled to a tiny, medium, or large required for that item. If so, access to the associated source memory model, addresses passed between service functions code is not a requirement. and their clients must be based upon the same memory The pool of files must be processed in an appropriate model. manner so that they can generate a pool of linker-ready files. Other troubles for mixed-language development include The processing is carried out by compilers or assemblers, and (1) parameter-passing conventions used by the service possibly by various preprocessors or code generation tools. functions created in one language as opposed to the Once the pool of files has been processed correctly, a conventions used by the client functions created in a different corresponding pool of linker-ready files is created that the language; and (2) the library file format used by one language linker converts into an executable file. compiler as opposed to that used by a different compiler. A build processing utility such as "make" uses a descrip Some mixed-language pitfalls are not insurmountable. tion of the files and the processes for building a particular Certain problems may be overcome by supplying "glue" executable file, as shown in Figure One. By readng the last- around the client code that calls the service. The glue must modified date stamped on each file, as well as using the resolve any differences in the run-time assumptions made by information in the make source file, the make utility can the service functions and their clients. determine the minimum processing required to create a new executable that is up-to-date relative to its subcomponents. A Rainbow of Storage File Need. To better grasp how compiling technology has evolved, Well-Traveled Paths to Code Reuse let's reexamine the files required by an interpreter, by a basic Through the strategy of separate compilation, several compiler, and by a modern compiling system. Generally, the different applications may be produced by linking different process of creating executable files has become more combinations of linker-ready files. Some subdivisions of an September 1993October 32 Forth Dimensions I Figure One. 1 I included in the executable file by the linker. info about build interface file for interface file for Routines that reside in library archive files are files and assoc 17 commands -1 -1 included in the executable only if the linker I determines the need for them by scanning the other linker-ready files that comprise the application. If a routine in the library archive date program date program is referenced by the external code in a normal last source file for last source file for linker-ready file, the linker extracts its precompiled code from the archive and includes it in the executable file. If a routine in the library is not referenced by external code, it is not included in the executable file (unless an already extracted routine depends on it). At least for library files, the linker must determine which routines are called by other routines, accounting for all the interdepen- dencies among the routines. To speed this process, traversal information included in- side the archve usually encodes all the interdependencies that exist among the li- brary routines. Most of the content of the linker-ready files is dictated by hardware rather than high- level languages. This helps make libraries fundamentally language-independent. The "intermediate code format" is much closer to the machine language than to any high-level language. Even if we are considering the linker-ready file for the Standard C Library, last executable file we cannot assume that its language of origin mod is C. (Was that a challenge you heard?) The source language in which accompa- nying interface descriptions are supplied tends to wed a library to a high-level language. application may be used repeatedly in a variety of applica- However, a vendor is able to add support for another tions. A more common term for the subdivisions of applica- programming language with a minor addtion. By supplying tions is "modules." When referring to the linker-ready file for several interface (header) files-one for each different lan- a module, the term "object module" is frequently used. guag-ne object module is allowed to serve multiple Linker-ready files that are reused can be viewed as programming languages. So a Pascal compiler, if fed a suitable libraries because their handling is more alike than different. "interfacendeclaration file, could perform type checks against As shown in Figure One, the compilng of module 2 requires the parameters being passed to a C function for which no two interface files as well as the source code for module 2. defining source code was submitted. One of the interface files serves the library, and one serves module 1. Once module 1 is stable, the make utility uses the Your Turn Now same minimal processing for it that is used for library A. The The sophistication of library tools, and of the underlying minimum processing for module 1 eliminates the compila- technique of separate compilation, deserves our attention tion step because the previously created object module and our assimilation into Forth. For good reasons, there is remains upto-date. never likely to be a retreat to simpler methods or tools. So we The modules that are reused the most are usually collec- should plan on adding this support to Forth as a complement tions of routines that perform one type of service, such as string to Forth's native compiling provisions. processing. To make these collections of routines easier to We have explored the advances that have occurred with remitherindividually or as a group-additional develop regard to application development tools, particularly in terms ment tools can be used to repackage them as library files. of compiling strategies. I hope I have not made any major Libraries involve a slight elaboration of the feature of guffaws in this attempt to create a tutorial out of my limited separate compilation. First, they establish an alternative understanding of this material. If so, I apologize. (Okay, so format for files that are considered linker-ready files. Second, I might have stretched the truth when I said that three kinds they are processed differently by the linker. of files were needed for support of separate compilation. I Routines that reside in normal linker-ready files are overlooked the header files.) Forth Dimensions 33 September 1993 October FIG Chapters I The Forth lnterest Group Chapters listed below are currently IOWA NEW YORK registered as active with regular meetings. lfyour chapter listing Central Iowa FIG Chapter Long Island Chapter is missing or incorrect, please contact the FIG office's Chapter 1st Tues., 730 p.m. 3rd Thurs., 7:30 p.m. Desk. This listing willbe updatedregularly in Forth Dimensions. Iowa State Univ. Brookhaven National Lab If you would like to begin a FIG Chapter in your area, write for 214 Comp. Sci. AGS dept., bldg. 911, lab rm. A-202 a "Chapter Kit and Application. " Rodrick Eldridge Forth lnterest Group (515) 294-5659 Irving Montanez P.O. Box 2154 (516) 282-2540 Oakland, California 94621 Fairfield FIG Chapter 4th Day, 8:15 p.m. Gurdy Leete (515) 472-7782 Rochester Chapter Monroe Comm. College MARYLAND Bldg. 7, Rm. 102 MDFIG Frank Lanzafame 3rd Wed., 6:30 p.m. (716) 482-3398 U.S.A. JHU/APL, Bldg. 1 San Diego Chapter ALABAMA Parsons Auditorium OHIO Thursdays, 12 Noon Huntsville Chapter Mike Nemeth Columbus FIG Chapter Tom Konantz Guy Kelly (619) 454-1307 (301) 262-8140 (eves.) 4th Tues. (205) 881-6483 Kal-Kan Foods, Inc. Silicon Valley Chapter MASSACHUSE-ITS 5 115 Fisher Road ALASKA 4th Sat., 10 a.m. Boston FIG Terry Webb Applied Bio Systems Kodiak Area Chapter 3rd Wed., 7 p.m. (614) 878-7241 Foster City Ric Shepard Bull HN Box 1344 John Hall 300 Concord Rd., Billerica Dayton Chapter Kodiak, Alaska 99615 (415) 535-1294 Gary Chanson (617) 527-7206 2nd Tues. & 4th Wed., 630 p.m. CFC ARIZONA Stockton Chapter MICHIGAN 11 W. Monument Ave. 612 Phoenix Chapter Doug Dillon (203) 931-2448 Detroit/Ann Arbor Area Gary Ganger (513) 849-1483 4th Thurs., 7:30 p.m. Bill Waiters Arizona State Univ. COLORADO PENNSnVANIA (313) 731-9660 Denver Chapter Villanova Univ. Chapter Memorial Union, 2nd floor (313) 861-6465 (eves.) Dennis L. Wilson 1st Mon., 7 p.m. 1st Mon., 7:30 p.m. (602) 381-1146 ' Clifford King (303) 693-3413 MINNESOTA Villanova University MNFIG Chapter Dennis Clark CALIFORNIA FLORIDA (215) 860-0700 Los Minneapolis Angela Chapter Orlando Chapter Fred Olson Every other Wed., 8 p.m. TENNESSEE 4th Sat., 10 a.m. (612) 588-9532 (except Nov., Dec.) Herman B. Gibson East Temessee Chapter Joslyn Center (305) 855-4790 MISSOURI Oak Ridge 339 Sheldon, El Segundo Kansas City Chapter 3rd Wed., 7 p.m. GEORGIA Sci. Appl. Int'l. Corp., 8th John LuValle 4th Tues., 7 p.m. FI. (818) 797-1820 Atlanta Chapter Midwest Research Institute 800 Oak Ridge Turnpike Richard Secrist (615) 483-7242 Howard Rogers 3rd Tues., 7 p.m. MAG Conference Center Emprise Corp., Marietta (301) 532-3342 Linus Orth (913) 236-9189 Don Schrader (404) 428481 1 TEXAS North Bay Chapter St. Louis Chapter Austin Chapter ILLINOIS 2nd Sat. 1st Tues., 7 p.m. Matt Lawrence 12 noon tutorial, 1 p.m. Forth Cache Forth Chapter Thornhill Branch Library PO Box 180409 2055 Center St., Berkeley Oak Park Robert Washam Austin, TX 78718 Leonard Morgenstern Clyde W. Phillips, Jr. 91 Weis Drive Dallas (415) 376-5241 (708) 713-5365 Ellisville. MO 6301 1 Chapter 4th Thurs., 7:30 p.m. Orange County Chapter Central Illinois Chapter NEW JERSEY Texas Instruments 4th Wed., 7 p.m. Champaign New Jersey Chapter 13500 N. Central Expwy. Semiconductor Cafeteria Fullerton Savings Robert Illyes (217) 359-6039 Rutgers Univ., Piscataway Huntington Beach Nicholas G. Lordi Conference Room A Noshir Jesung (714) 842-3032 INDIANA Warren Bean (214) 4%3115 (908) 932-2662 Fort Wayne Chapter Sacramento Chapter 2nd Tues., 7 p.m. NEW MEXICO 4th Wed., 7 p.m. I/P Univ. Campus Albuquerque Chapter 17W59th St., Room A 871 Neff Hall 1st Thurs., 7:30 p.m. Bob Nash Blair MacDermid Physics & Astronomy Bldg. (916) 487-2044 (219) 749-2042 Univ. of New Mexico Jon Bryan (505) 298-3292 September 1993 October 34 Forth Dimensions INTERNATIONAL Houston Chapter AUSTRAUA ENGLAND JAPAN 3rd Mon., 730 p.m. Melbourne Chapter Forth Interest GroupUK Japan Chapter Houston Area League of 1st Fri., 8 p.m. London Toshio Inoue PC Users (HAL-PO Lance Collins 1st Thurs., 7 p.m. University of Tokyo 1200 Post Oak Rd. 65 Martin Road Polytechnic of South Bank Dept. of Mineral Develop (Galleria area) Glen Iris, Victoria 3146 RM 408 ment Russell Harris 03/889-2600 Borough Rd. Faculty of Engineering 013) 461-1618 BBS: 61 3 809 1787 D.J. Neale 7-3-1 Hongo, Bunkyo-ku 58 Woodland Way Tokyo 113, Japan VERMONT Sydney Chapter Morden, Suny SM4 4DS (81)3-3812-2111 ext. 7073 Vermont Chapter 2nd Fri., 7 p.m. Vergennes John Goodsell Bldg., RM LC19 FINIAND REPUBLIC OF CHINA 3rd Mon., 730 p.m. Univ. of New South Wales FWIG R.O.C. Chapter Verge~esUnion High School Peter Tregeagle Janne Kotiranta Ching-Tang Tseng RM 210, Monkton Rd. 10 Bin& Rd. Arkkitehdinkatu 38 c 39 P.O. Box 28 Hal Clark (802) 453-4442 Yowie Bay 2228 33720 Tampere Longtan, Taoyuan, Taiwan 02/524-7490 +358-31-184246 (03) 4798925 VIRGINIA Usenet: First Forth of [email protected] GERMANY SWEDEN Hampton Roads Germany FIG Chapter SweFIG William Edmonds BELGIUM Heinz Schnitter Per Alm (804) 898-4099 Belgium Chapter Forth-Gesellschaft e.V. 46/8-92963 1 4th Wed., 8 p.m. Postfach 1110 Potomac FIG Luk Van Loock D-8044 Unterschlei13heim SWITZERLAND D.C. & Northern Virginia Lariksdreef 20 (49) (89) 317 37 84 Swiss Chapter 1st Tues. 2120 Schoten Munich Forth Box: Max Hugelshofer Lee Recreation Center 03/658-6343 (49) (89) 871 45 48 Industrieberatung 5722 Lee Hwy., Arlington 8N1 300,1200,2400 baud Ziberstrasse 6 Joseph Brown Southern Belgium Chapter e-mail uucp: 8152 Opfikon (703) 471-4409 Jean-Marc Bertinchamps [email protected] 01 810 9289 E. Coast Forth Board Rue N. Monnom, 2 Internet: (703) 442-8695 B-6290 Nalinnes [email protected] 071/213858 Richmond Forth Group 2nd Wed., 7 p.m. CANADA 154 Business School Forth-BC Univ. of Richmond 1st Thurs., 7:30 p.m. Donald A. Full BCIT, 3700 Willingdon Ave. (804) 739-3623 BBY, Rm. 1A-324 Jack W. Brown WISCONSIN (604) 596-9764 or Lake Superior Chapter (604) 436-0443 2nd Fri., 7:30 p.m. BCFB BBS (604) 434-5886 Why FIG Chapters? 1219 N. 21st St., Superior See the editorial on this issue for news from the Allen Anway 015) 394-4061 ~o,-th- Chapter new chapter in southern Wisconsin... 4th Thurs.. 7-93 p.m. N. Alta. 1nk. of ~ech. Tonv Van Muvden 1 (4031 486d(days) (403) 962-2203 (eves.) HOLLAND SPEClAL GROUPS Holland Chapter Forth Engines Useis Grou Southern Ontario Chapter Maurits Wijzenbeek John carpenter Quarterly: 1st Sat. of Mar., Nieuwendammerdijk 254 1698 Villa St. June, and Dec. 2nd Sat. of Sept. IX Mountain View, CA 94041 Genl. Sci. Bldg., RM 212 The Netherlands (4 15) W-1256 (eves.) McMaster University ++(20) 636 2343 Dr. N. Solntseff (416) 525-9140 x3443 ITALY FIG Italia Marco Tausel Via Gerolamo Forni 48 20161 Milano Forth Dimensions 35 September 1993 October ("Back Burne~," continued from page 39.) nents of the Forth environment reside in application RAM, so or one of the fig-Forth listings and the accompanying they must be created anew each time the application implementation notes, it should quickly become apparent hardware is powered up or reset. that the assembly language approach is rather convoluted, Once initialization is complete, the Forth virtual machine and not for the faint of heart. must be started (i.e., activated). The machine is started by Interestingly, Ting utilizes the Microsoft 80x86 macro assigning it a word-the application program-to execute. assembler, rather than a cross-assembler, regardless of the Once started, the machine never stops, apart from reset, a application hardware. If, however, a cross-assembler is used, system crash, or power failure. The programmer must ensure porting (transporting) Forth between various platforms will that the machine always has something to do. He does thls be considerably simplified when the cross-assembler is of the by writing the application program in the form of an endless "universal"(i.e., table-driven) variety. Such assemblers retain loop. the same syntax, irrespective of the processor; the table for each processor provides a set of processor-specific opcodes. The Bare Essentials The process of converting an assembly language file for one We shall assume the following resources: assembler to work with another assembler of incompatible the application hardware: a ROM-based computer, such as syntax can involve long hours of tedious editing. Represen- the 8051 trainer presented in column #5, with serial tative universal assemblers are TASM (shareware by Speech interface Technology, Issaquah, Washington) and Cross-32 (Universal the development system: a computer of the IBM PC genre, Cross Assemblers, Nova Scotia, Canada). providing mass storage (futed disk) and serial interface, as The metacompilation approach makes use of Forth in the well as keyboard and text-oriented screen for operator development environment to define Forth for the application interface environment. The approach is not generally understood and (alternative A) a cross-assembler and a compatible text has been shrouded with an undeserved mystique. Many editor, both running on the development system; the cross- consider it an esoteric technique which is strictly within the assembler produces code which is to execute on the domain of the Forth guru. This is a false impression. application hardware Metacompilation is the most simple, most direct method of (alternative B) a Forth environment, sans metacompiler, porting Forth from one system or platform to another. running on the development system Granted, you must know what you are doing. However, once you understand what is going on, the process frees you from Although we will use as our application platform the 8051 a confusing mass of detail and from a multitude of con- trainer, the term application does not imply a limitation of straints. capability: in general, the application system may itself be a development system, and the Forth environment imple- Follow the Yellow Brick Road mented on the application hardware may include a meta- With metacompilation, the procedure is as follows: within compiler. Indeed, the application system and the develop- the Forth development environment, we write: ment system may be identical, even to the extent that they are an assembler for the instruction set of the application one and the same. This latter case occurs particularly if you processor are implementing Forth without having access to a Forth a metacompiler which incorporates the assembler development ~nvironment,or if you are reconfiguring an application source (a mixture of Forth code words and existing Forth environment. high-level Forth words) application startup code, i.e., source for initialization of the The Scenic Route application system (Forth code words) Given these resources, there are two alternative routes by which we may reach our goal. While we are in the Forth development environment, we What at first appean to be the most straightforward load the metacompiler, just as we would load any other Forth approach utilizes assembly language to define each compo- application which runs on the development system. We then nent of Forth for the application environment. The assembler load the source code for the application. The metacompiler or cross-assembler runs on the development system, produc- operates on the source code as it is loaded, producing ing code which is to run on the application hardware. Once application object code. Finally, we copy the application the assembly source has been debugged and a Forth object code from the development system to ROM or floppy environment has successfully been implemented on one disk. application platform, the same source code may be used as Although the assembly language approach is adequate the basis for implementing Forth on other platforms. for the task of creating a new Forth environment, metacom- The assembly language approach is used by R.G. Loeliger pilation facilitates the process by placing at the disposal of the in his book 7Waded Zntepretive Languaga (Byte Books, programmer the full resources of the Forth language. Specific Peterborough, New Hampshire, 1981). The approach is also advantages of metacompilation over the assembly language the method originally used to distribute fig-Forth circa 1980 approach include: and is, in principle, the approach used in the eFORTH system The word compilation mechanism inherent in Forth is of C.H. Ting. If you take the trouble to inspect Loeliger's book utilized to create heads and parameter fields within the September 1993 October 36 Forth Dimensions I application dictionary. believe that Payne's approach is unnecessarily complex: The programmer is free to implement whatever assembler there is too much source code and the procedures are too syntax he finds convenient. involved. After all, the complete body of source code for Diagnostic words may be defined and executed interac- native-mode plyFORTH for the DEC PDP/LSI-I I-a micro- tively. computer with the instruction set of a minicomputer (a really mawelous machine, a joy to program)-occupies only 83 Checking Out the Competition sparsely populated 1024-byte screens. Moreover, the poly- The book Embedded ControllerForthforthe8051 Family FORTH system has an integral metacompiler. by W.H. Payne (Academic Press, Boston, 1990) follows the metacompilation approach. I hesitate to recommend the text, Pulling Yourself Up inasmuch as I find it rather disorganized andunapproachable. by Your Own Bootstraps Moreover, I disagree with a number of Payne's statements If you find yourself without access to a Forth development and the conclusions they imply. One paragraph in particular environment, it would not be unreasonable to reson to the illustrates my objections; in it, Payne says: assembly language approach in order to build a Forth development environment, so as to enable further develop- The text of this book is its least important aspea. The code ment to be conducted via metacompilation. In fact, Payne's presented in this book warrants your greatest study. Charles book assumes just such a scenario, and Payne provides code Moore's genius is brought you members ofthe Forth for virtually everything in the way of software needed by Interest Group. Jerry Boutelle's genius with metacompilers those taking this tack. allows us to generate Forth from source. You can figure out what Charles Moore had in mind fairly easily. Understanding what Jerry is doing in the metacompiler baffles the best Whence? programmers. Since this column (6))is devoted to the matter of orientation, perhaps we should recall what we have covered In this OntheBackBurnerseries on metacompilation, the in previous columns. Column #3 announced a focus upon code is the least important aspect. Code fragments which I the field of embedded systems, with special emphasis on the present are not optimized (nor are they guaranteed to work subject of metacompilation. Column #4 described and pro- correctly). They are only examples, to facilitateyour compre- vided listings for an 8051-family assembler, a key component hension. If you understand the text, you will be able to write of a metacompiler. The fifth column (no pun intended) your own code, and your code will, in most cases, be presented plans for an 8051-family single-board computer superior to that of the examples. for use as a metacompilation trainer. Column 6consisted of It should be noted that, whereas the metacompiler to a foray into the terminology associated with metacompila- which Payne refers apparently is straight from the hand of tion. Column #7 dealt with the Forth vocabulary structure and Boutelle, the fig-Forth listings to which Payne refers do not with the utilization of vocabularies in the process of meta- necessarily convey the genius of Chuck Moore, inasmuch as compilation. Column #8 dscussed pointers and some of the they are removed by several generations from his direct intricacies of stack implementation. influence. A metacompiler is not inhemtly a complex application, Whither? nor is metacompilation inhemtly a complex process. A What's in store? If we simply sit down in front of a terminal properly designed metacompiler should not baMe a pro- and begin typing grarnrner. A design is a solution to a problem. A fundamental criterion of excellence in design is simplicity. Simplicity in : METACOMPILER design is the hallmark of a designer who understands the problem. we won't get very far unless we have in our minds a clear Designs of the Rube Goldberg variety typically indicate picture of the elements which comprise a Forth system and either that the designer did not understand the problem at how each element fits into the whole. Thus, you see the hand, or that he faced overwhelming constraints. (It may well reason for digressions to discuss matters such as assemblers be that adding metacompilation capability to dudFORTH and vocabularies. Our next investigation will explore thread- admits of no good solution.) ing and the inner interpreter. Stay tuned. Meanwhile, drop The foregoing is not meant to imply that every code me a line. segment should be transpamt. As with a mating combina- R.S.V.P. tion in chess, excellent code may sometimes be abstruse, although it often is the essence of simplicity. Code of hs category should always be documented. Admittedly, my effort in thls metacompilation series is Russell Harris is an independent consultant providing engineering, program- parallel to that of Payne. The fact that I chose the same mma, and technical documentation services to a varietv of industrialclients. His I a~~licationDlatform (the 8051) as did Pavne is ~urelv/ main~nterestslie in writing and teaching, and in workingwith embedded systems in the fields of instrumentationand machinecontrol.Hewelcomesclientswhooffer a matter circumstance. my pur- him the opportunity to work with Forth. He can be reached by phone at 7 13461- pose is not to duplicate Payne's treatment of the subiect. '1I 1618, by facsimile at 713-461-0081, by mail at 8609Cedardale Drive, Houston, I - / Texas 77055. or on GEnie (address RUSSELL.H) Forth Dimensions 37 September 1993 October (Character classrjication, continued fronapage 8.) the source operand is somewhere in the lookup table at -ctype, as indicated by that register. Had we wanted to emulate the C code exactly, the place FORTH and Classic to implement the necessary 1+ would have been to change the byte displacement value to a 1. This would have added two bytes to the size of the table: the byte at -ctype, and Computer Support one byte of wastage due to word alignment required by the For that second view on FORTH appli- processor. But, unlike the C macros, it would not have added any instructions to the code. cations, check out The Computer Journal. If you Line ten places the results on the stack, and line 11 sets run a classic computer (pre-pc-clone) and are our return to the calling code. interested in finding support, then look no Note that the result is not necessarily a one, minus one, fbrther than TCJ. We have hardware and soft- or a zero. The result is the product of the and between the ware projects, plus support for Kaypros, S 100, bit mask in the classifier word and the mask in the array. Thls is not a "standard" implementation. However, the user may CP/M, 6809's, and embedded controllers. find the resulting bit mask useful for further processing, and Eight bit systems have been our mainstay the zero or non-zero result is useful. for TEN years and FORTH is spoken here. We Even with fastForth's efficient compiler, the assembly provide printed listings and projects that can run language version of the code is somewhat faster than the on any system. We also feature Kaypro items high-level version, and considerably smaller. from Micro Cornucopia. All this for just $24 a Screen 1926 uses the defining word CLASSIFIER to build several classification words, analogous to the macros year! Get a FREE sample issue by calling: in the second group in ctype.h. There are single-bit mask (800) 424-8825 words, such as ISLOWER and ISUPPER. Masks may be or'd together to produce larger classifications. An example of the latter is ISALPHA, which tests for a character being either an upper- or lower-case character. TCeB:Eter Results Lincoln, CA 95648 The exercise produced clean code, easily understood (with the possible exception of the assembly language), and very fast. The code probably takes more space than the code it was written to replace, but the user may find that the added flexibility is well worth it. The whole processfrom being dissatisfied with Mr. Schaaf's code, reverse engineering the C code, writing the code in Forth (including the assembly language), and testing the Forth code-took less than two hours. It took longer to write this article. Availability This code is released to the public domain. Enjoy it in good health, and toast the health of contributors to the public domain from time to time. CharlesCurley, a long-time Forth nuclear guru, has his own private postal code: 827 17-2071. Computer Journal ...... 38 THIRTY-DAY FREE OFFER - Fma MMSFORTH Forth Interest Group ...... centerfold, 40 GAMES DISK worlh $39 95 wltn pbrcnase of MMSFORTH Svsfem CRVPTOOUOTE HELPER OTHEL-0. BREA<- Harvard Softworks...... 17 FORTH and others Miller Microcomputer Services ...... 38 Silicon Composers ...... 2 September 1993 October 38 Forth Dimensions A Panorama Several readers have expressed confusion concerning both our ultimate goal and the means of achieving it. Our goal is to implement a Forth environment on a cornput& we term the mlication hadware. We accom- plish ou goal by using a computer, the deaelqnentsystem, Who'S on First3 to generate code which, when executed on the application hardware, first creates a Forth environment and then acti- vates the environment. Having generated executable application code in the development environment, we copy the code to disk or to ROM, according to the configuration of the application Conducted by Russell L. Harris hardware. On hardware such as the IBM PC, application Houston, Texas code typically executes from RAM and must be loaded into RAM from disk. On hardware such as the 8051 single-board computer (SBC) presented in column 6,application code Column #7 generated a brief flurry of response, a total of executes directly from ROM. ten contacts (from a circulation of 1600?). I need feedback on a continual basis, in order to match the presentation to your The Kick-Off background and level of understanding. Particularly, I need The segment of the application code which first receives to hear from anyone who finds details of a presentation control of the processor is termed the initialization code. In unclear. If you don't quite understand what's going on, our usage, the term will embrace creation and activation of you're probably not alone. However, since we're not in a the Forth environmen4 as well as configuration of the classroom where I can look for blank faces and puzzled hardware. expressions, you must take the initiative and contact me Most computer systems contain one or more hardware whenever you hit a snag. I will try to get you over the components which can assume a variety of configurations immediate hurdle; then, in a subsequent column, I will (i.e., behaviours). The processor, the serial interface adapter, backtrack and elaborate on those areas you found unclear. and the parallel interface adapter typically are of this nature. Serial communication parameters and the direction (i.e., Breaking the Ice input or output) of parallel ports are representative of Don't let things pile up: In any classroom environrnent, behaviours which vary with component configuration.Origi- as soon as you see that you're lost, interrupt the lecture and nally, component configuration was accomplished by state the area in which you are confused. You will be jumpering pins of the respective integrated circuit. Now, surprised how many of your fellow students are confused on however, configuration is typically done under program the same point, but were too embarrassed to be the first to control, by loading specified values to registers within the admit it. By speaking out, you benefit everyone: you, your devices. classmates, and the teacher. Understanding is built upon Hardware configuration is the first task performed by the understanding: Fundamental concepts which are not mas- initialization code. After configuring the hardware, many tered at first encounter can quickly snowball into insur- initialization routines perform a checksum or cyclic redun- mountable barriers. dancy check (CRC) on system ROM and a read/write An aside: A lecturer who disallows interruptions, insists diagnostic on system RAM. upon unquestioning submission to his "authority,"or brands If the application hardware is a disk-based system such as as heresy any challenge of "facts" or theories he presents, the IBM PC, the ROM BIOS furnished with the PC is should immediately be suspect. Truth welcomes--nay, responsible for hardware initialization. Thus, the initializa- demands-scrutiny. In this regard, you may find interesting tion portion of Forth application code running on a PC need Albert Einstein's essay "On Education" (1936). concern itself only with setting up and activating the Forth Regarding the level of presentation, I intend this column environment. If the application hardware is a ROM-based to be easily comprehensible by anyone who has successively system such as our 8051 trainer, the application code we navigated the text Stam'ng Folth by Leo Brodie/FORTH, Inc. generate will both configure the hardware and set up and Our current topic, metacompilation, is not a terribly ad- activate the Forth environment. vanced subject! Another aside: I doubt if even half thase who think they The Set-Up have mastered Starting Forth have in reality done so. The process of setting up the Forth environment involves Although the topics covered in Statn'ng Fotth are not difficult, reassignment of interrupt vectors, definition and initialization the book itself is deceptively elementary. Unless you have of pointers which bring into existence the stacks, buffers, personally worked through each of the exercises, you I dictionary, etc., and definition and initialization of pointers probably have failed to comprehend a number of critical which constitute the user area of OPERATOR.These compc- concepts. Forth Dimensions 39 September 1993 October 6 s5 nal techcal conference rogrammers, managers, vendors, and users Following Thanksgiving November 26-November 28,1993 Asilomar Conference Center Monterey Peninsula overlooking the Pacific Ocean Pacific Grove, California U.S.A. Theme: Forth Development Environment Papers are invited that address relevant issues in the establishment and use of a Forth development environment. Some of the areas and issues that will be looked at consist of networked platform independence, machine independence, kernel independence, development system/application system independence, human-machine interface, source management and version control, help facilities, editor development interface, source and object libraries, source block and ASCII text independence, source browsers including editors, tree displays and source data-base, run-time browsers including debuggers and decompilers, networked development/target systems. Mail abstracts of approximately 100 words by September 1,1993. Completed papers are due November 1,1993. Registration fee for conference attendees includes registration, coffee breaks, notebook of papers submitted, and for everyone rooms Friday and Saturday, all meals including lunch Friday through lunch Sunday, wine and cheese parties Friday and Saturday nights, and use of Asilomar facilities. Conference attendee in double room- $380 Non-conference guest in same room - $260 Children under 18years old in same room - $160 Infants under 2 years old in same room - free Conference attendee in single room - $490 *** Forth lnterest Group members and their guests are eligiblefor a ten percent discount on registration fees. *** John Hall, Conference Chairman Robert Reiling, Conference Director Register by calling, fax or writing to: Forth Interest Group, P.O. Box 2154, Oakland, CA 94621, (510) 893-6784, fax (510) 535-1295 This conference is sponsored bv FORML, an activity of the Forth Interest Group, Inc. (FIG). The Asilomar Conferencecentercombines excellentmeeting and comfortable living accommodationswith secluded forestson aPacific I ocean beach. Registration includes use of conference facilities. deluxe rooms. all meals. and nirrhtlv wine and cheese ~arties. I