198012 Byte Magazine Vol 05 12 Adventure

DECEMBER 1980 Volume 5, Number 12 $2.50 In USA/$2.95 in Canada 3 @ 7 \ = » AMCGRAW- HILL PUBLICATION the small systems jot irnal y i> — t] yaw pimo Aujnbuj uo Lee 191199 WHAT ARE YOU LOOKING FOR IN A SYSTEM? VERSATILITY — Data bus—motherboard design allows you to configure a system to the end users exact needs. EXPANDABLE — Minimum RAM capacity 56K Expandable to 768K. Two I/O ports — Expandable to seventeen. MASS STORAGE- 3.0 M/bytes on 5%” flexible disks. (4 drives) 5.0 M/bytes on 8 inch flexible disks—(4 drives) 40 M/bytes on “Winchester” fixed disk. SOFTWARE — Operating System — Multitasking, multiuser with memory management. Languages — FORTRAN, Pascal, BASIC, PILOT Utilities — Debug, Sort-Merge, Diagnostics — over 40 others. Data Processing — General Ledger, Receivables, Payables, Payroll, Jobcost, Mail List, Inventory, Record Management System. Word Processing — Text Editor and Processor — device independent with proportional spacing bidirectional printing. COST EFFECTIVE—System consisting of 128K processor, terminal, and 2.4 M/byte dual eight-inch disk drives — less than $6,000.00 (O.E.M. 100 quantity) SOUTHWEST TECHNICAL PRODUCTS CORPORATION Li 219 W. Rhapsody CC San Antonio, Texas 78216 (512) 344-0241 Cromemco accepts your challenge, Data General a Data General, we saw your ad. So we realize you hope to win over some of our computer business. And we can see you have reason to be pleased about your line of minicomputers. They are MINIs But Cromemco produces state- of-the-art MICROcomputers. Powerful ones. And our micros have some outstanding advantages. For example, Cromemco is the only microcomputer manufacturer to support a broad range of though. microcomputers with (a) _5-inch WE'RE BUSTING THE COMPETITION’S BOARDS AGAIN. Reproduced from the July 31, 1980 issue of Electronics magazine. ‘in original ad Cirote 1 on Inquiry card. Cromemeo togo on computer board shown are and MBC/}. Data Cone aanits amily © micoNGVA™ boat They're the best comy board mone x and parelle! 1/0 tines, walre support fron Our famous mucro of system. You even The competition vl always Sing the praises o! their ttle single yoard computers. But from now falsetto neo double-sided, double-density floppy disk drives and with (b) 8-inch double-sided, double-density Floppy disk drives AS WELL AS (c) 8-inch Winchester hard disk drives. That means, of course, that our customers have a wide choice of disk storage capability. UNEQUALLED SOFTWARE SUPPORT OK. That was one point. Here’s another: our stunning selection of software support, Cromemco_is the only micro manufacturer to produce both single-user and multi-user multi- tasking computers with software like This: SYSTEM SOFTWARE © CDOS (a CP/M-like operating, system) CROMIX (a UNIX-like operating system) RPG-I! (IBM-compatible) COBOL BASIC FORTRAN IV RATFOR LISP c Macro Assembler APPLICATION SOFTWARE Word Processing System Data-Base Management General Ledger Accounts Receivable Accounts Payable Inventory All of this is available now with So there you are, D.G. You can see why we know our microcomputers will stand the test. Cromemco eagerly accepts the challenge. Cromemco” f 1b. oor ate Torherrow’ s Computers Today 280 BERNARDO AVE. MOUNTAIN VIEW, CA 94043, (415) 964-7400 © TWX 910-379-6988, BYTE Decembet 1980 1 Management Information Display Ultrasonic heart sector scan High-resolution display with alphanumerics Get the professional color display that has BASIC/FORTRAN simplicity LOW-PRICED, TOO Here’s a color display that has everything: professional-leve} resolution, enormous color range, easy software, NTSC conformance, and low price. Basically, this new Cromemco Model SDI* is a two-board interface that plugs into any Cromemco computer. The SDI then maps computer display Memory content onto a convenient color monitor to give high-quality, high- resolution displays (756 H x 482 V pixels). When we say the SDI results in a high- quality professional display, we mean you can’t get higher resolution than this system offers in an NTSC-conforming display. The resolution surpasses that of a color TV picture. BASIC/FORTRAN programming Besides its high resolution and low price, the new SDI lets you control with optional Cromemco software packages that use simple BASIC- and FORTRAN- like commands, Pick any of 16 colors (from a 4096-color palette) with instructions like DEFCLR (c, R, G, B). Or obtain a circle of specified size, location, and color with XCIRC (x, y, F, C). °U,S, Pat. No, 4121283 Circle 1 on Inquiry card. Model SDI High-Resolution Color Graphics Interface HIGH RESOLUTION The SDI’s high resolution gives a professional-quality display that strictly meets NTSC requirements. You get 756 pixels on every visible line of the NTSC standard display of 482 image lines. Ver- tical line spacing is 1 pixel. To achieve the high-quality display, a separate output signal is produced for each of the three component colors (red, green, biue). This yields a sharper image than is possible using an NTSC-composite video signal and color TV set. Full image quality is readily realized with our high- quality RGB Monitor or any conventional fed preeny bide monitor common in TV work, ‘Mode! SDI plugs into Z-2H 11-megabyte hard disk computer or any Cromemco computer DISPLAY MEMORY Along with the SDI we also offer an optional fast and novel two-part memory that gives independent high-speed access to the computer memory. The two-port memory stores one full display, permit- ting fast computer operation even during display. CONTACT YOUR REP NOW The Model SDI has been used in scien- tific work, engineering, business, TV, color graphics, and other areas. It's a good example of how Cromemco keeps computers in the field up to date, since it turns any Cromemco computer into an up-to-date color display computer. The SDI has still more features that you should be informed about. So contact your Cromemco representative now and see all that the SDI will do for you. Cromemco inecoerp 280 BERNARDO AVE., MOUNTAIN VIEW, CA Tomorrow's computers today 94040 © (415) 964-7400 page 90 page 142 Foreground 24 MULTIMACHINE GAMES by Ken Wasserman and Tim Stryker The most exciting computer games are those with two machines and two or more players. 44 COMPUTERIZED TESTING by Steve Ciarcia A computer is useful for automating any process—even hardware testing. 96 GRAPHIC COLOR SLIDES, PART 2 by Alan W Grogono This month we demonstrate the use of subroutines to generate equation plots, histograms, regression and monthly analysis graphs. 120 MICROGRAPH, PART 2: VIDEO-DISPLAY PROCESSOR by E Grady Booch Part 2 details more about this surprisingly simple high-resolution video display. 192 PIRATE'S ADVENTURE by Scott Adams The man who first brought Adventure games to microcomputers gives us an entire listing of one of his most enjoyable games. 244 A POCKET COMPUTER? SIZING UP THE HP-41C by Bruce Carbrey This device comes close to being the world’s first pocket-sized personal computer. 268 LOST DUTCHMAN'S GOLD by Bob Liddil and Teri Li Applesoft BASIC is well suited to the writing of games, as this program shows. Background 142 A SIMPLIFIED THEORY OF VIDEO GRAPHICS, PART 2 by Allen Watson II Explanations of color-video techniques and some of the quirks of mitroprocessor systems are provided, 158 ON THE ROAD TO ADVENTURE by Bob Liddil fons with a survey of the major Adventure games, here's an explanation of how to play them. 172 ZORK AND THE FUTURE OF COMPUTERIZED FANTASY SIMULATIONS by P David Lebling One of the authors of Zork describes his game and how similar games may appear in the future. 186 CHARACTER VARIATION IN ROLE-PLAYING GAMES by Jon Freeman A variable set of character traits can be used to create a game of high adventure that is different every time you play it. Product Reviews: Games 74 DUNGEON CAMPAIGN; 78 A STELLAR TREK; 84 MORLOC’S TOWER; 90 ODYSSEY: THE COMPLEAT APVENTURE; 114 SARGON Il; 264 MICROSOFT ADVENTURE; 282 COMPUTER BISMARCK Nucleus 6 Editorial: What's Wrong With er 325, 326 BYTE's Bits Technical Writing Today? 306 Clubs and Newsletters 14 Letters 314 Event Queue 94 Technical Forum: The Twelve 318 Ask BYTE Computerized Days of Christmas 322 Books Received 214 BYTELINES 324 Software Received 222 User's Column 342 What's New? 288 Programming Quickies: 398 Unclassified Ads Monster Combat 399 BOMB, BOMB Results 294 BYTE's Bugs 400 Reader Service December 1980 © BYTE Publications Inc 3 Publishers Virginia Londoner, Gordon A Williamson Associate Publisher John E Hayes Assistant Cheryl A Hurd Founding Editor Cari T Helmers Jr Editor-in-Chiet Christopher P Morgan Editors Richard S Shuford, Gregg Williams, Curtis P Feigel, Harold Nelson Stan Miastkowski Consulting Editor Mark Dahmke Book Editor Bruce A Roberts Chief Copy Editor David W Hayward Copy Editors Faith Hanson, Warren Williamson, Rabin M Moss, Anthony J Lockwood Assistant to the Editors Falth Ferry Assistants Dabe Wheeler, Karen A Cillay New Products Editor Clubs, Newsletters Charles Frelberg Drafting Jon Swanson Production Director Nancy Esile Assistant Production Director Christine Dixon Production/Advertising Coordinator Wai Chiu LI Production Art Holly Carmen LaBossiere, Deborah Porter Chiet Typographer Sherry McCarthy Typographers Debi Fredericks, Donna Sweeney, Valerie Horn Advertising Director Thomas Harvey Assistants Ruth M Walsh, Ms. Marion Gagnon Barbara J Greene, Rob Hannings Special Projects Coordinator Jill E Callinan Marketing Coordinator Laura A Hanson Circulation Manager Gregory Spitztaden Assistant Circulation Manager Andraw Jackson Assistants Agnes E Perry, Barbara Varnum, Louise Menegus, David Overbeck Deater Salen Melanie Bertoni Controller Danie! Rodrigues Aasistant Mary E Fiuhr Accounts Recelvable Specialist Karen Burgess Accounts Receivable Assistant Jeanne Cilley Receptionist Jacqueline Earnshaw Traitic Department Mark Sandagata, N Scott Gagnon In This Issue Although the mysteries and menaces lurking in the shadows of this issue's cover may exist only in the minds of an imaginative Adventure player or the cover artist, Robert Tinney, that doesn’t make them any less real to the person playing the game. This issue explores the many aspects of Adventure and Adventure-like games. It includes two complete Adventures in BASIC, an excellent in- troductory article (“On the Road to Adventure,” by Bob Liddil), two articles on the state of the art in Adventure games, and a hand- ful of game reviews. This issue also contains “Computer Testing,” an article by Steve Ciarcia, as well as the second parts of several articles continued from the November graphics issue: “Micrograph,” “Graphic Color Slides,” and “A Simplified Theory of Video Graphics.” Ollicers of McGraw-Hill Publications Company: Paul F McPherson, President; Executive Vice Presidents: Jamos E Boddor!, Gene W Simpson; Group Vice President: Oaniel A McMilian; Senior Vice President-Editorial: Ralph R Schulz; Vice Presidente: Kemp Anderson, Business Systems Development; Stephen © Croft, Manufacturing; Rober! & Doll, Circulation; James E Hackett, Controller; William H Hammond, Communications; Eric B Herr, Planning and Development; John W Palten, Sates: Edward & Schirmer, international Olticers of tha Corporation: Harold W McGraw Jr, President, Chief Executive Olficer and Chairman of the Board; Robert F Landes, Senior Vice Presidant and Secretary; Ralph J WebD, Treasurer. BYTE is published monthly by BYTE Publications Inc, 70 Main SI. Peterborough NH 03458, a wholly-owned subsidiary of McGraw Hi, Ine. Addrass ali mall except subscriptions to above address: phone (603) 924-8281. Address subscriptions, change of address, USPS Form 3579, and tullilment questions to BYTE Subscriptions, FO Box 580. Martinsville NJ 08838, Conlolied circulation postage aid at Waseca, Minnesota 56093 - USPS Pubiicatwon No 528890 {ISSN 0360-5280). Canadian second ciass registration number 9321 Subscriptions are $18 for one year, $32 for two years, and $46 for three years in the USA and its possessions. in Canada and Mextco. $20 for one yoar, $38 lor two years, $52 for thrae years $32 for one year ait delivery to Europe. $32 surface delivery elsewhare. Alt dolivery 10 selected arens at additional rates upon request Single copy price is $2.50 in he USA and ils possessions, $295 in Cenaca land Mexico, $4.00 in Europe, and $4.50 elsewhere. 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Dept PA, London WC1R 4EJ England Subscription WATS Line: (800) 258-5485 et cueaiaions Office hours: Mon-Thur 8:30 AM - 4:30 PM, Friday 8:30 AM - Noon, Eastern Time NATIONAL ADVERTISING SALES REPRESENTATIVES: NORTHEAST (617) 444-3948 MIDWEST (312) 864-3487 EAST & SOUTH (212) 682-5844 SOUTHWEST (714) 540-3554 Hajar Associates Halar Associates Hajar Associates NORTHWEST (415) 964.0708 280 Hillside Ave 2405 Lawndale 521 Fifth Ave Hajar Associates Needham Heights MA 02194 Evanston IL 60201 New York NY 10017 1000 Elwell Ct, Suite 227 Palo Alto CA 94303 4 December’ 1980 © BYTE Publications tne RS-170 com- posite or direct drive output Local or external sync generation 4or 5 Mhz Z80 micro- processor 60 hertz real- time clock 8 level interrupt tie-in IEEE S100 bus compatible Screenware™ Pak I A 4K byte operating system resident in PROM on MicroAngelo™ Pak I emulates an 85 char- acter by 40 line graphics terminal and provides over 40 graphics commands. Provisions exist for user-defined character sets and directly callable user extensions to Screenware Pak I. SCION Corporation 8455-D Tyco Road Vienna, Va. 22180 (703) 827-0888 MICROANGELO HIGH RESOLUTION GRAPHICS SINGLE BOARD COMPUTER by SCION CORPORATION. Light pen interface Time multi- plexed refresh 4K resident Screenware™ Pak I operating system 32K RAM isolated from host address space High speed communica- tions over parallel bus ports Host Resident Terminal Software An interface software package that coordi- nates input/output from the MicroAngelo™ graphics board, the MicroAngelo™ keyboard, and your computer. The result is a flexible, yet sophisticated graphics terminal. European Distributor: Micro Diversions UK Ltd. 17/19 Mesnes Street Wigan, England WN1 1QP 09-423 4311 Circle 2 on Inquiry card. Circle 3 on inquiry card, UCSD" PASCAL FORTRAN PORTABLE Develop on aZ-80t, run on LSI-114, T. f. 990, 6800 or vice versa EFFICIENT Structured, readable Speeds development X5 Easy maintenance POWERFUL Full standard Pascal or ANS! '77 FORTRAN plus extensions, Concurrency, multiple users soon. Cost-EFFECcTIVE Compiate system with compiler, editors, inter- preter, assembler and utilities from $350. Now AVAILABLE Operating System Compilers Programmer Utilities Data Base Management Word Processing Business and Medical Software Games, Home & Hobby POPULAR MICROS SuPPORTED DEC, Radio Shack, Apple, Microengine, CP/M§ based and others P C D SYSTEMS P.O. Box 143 Penn Yan, NY 14527 315-536-3734 Editorial What's Wrong with Technical Writing Today? Chris Morgan Editor-in-Chief In going through the scores of articles that cross my desk each month, I've begun to notice that many of them are poorly written. I’m talking here not so much about incompetent writing (although the number of spelling and syntax errors is alarming), but rather about misguided writing, writing that is difficult to read, unclear, or wasteful of the reader’s time. The problem is certainly not BYTE's alone, Editors of other magazines have told me much the same story. Thinking about possible solutions to the problem led me to write this editorial. The quality of technical writing affects all of our readers in one way or another. Whether you program for a living or just for fun, you need to write clear, concise documentation to accompany your programs. And you un- doubtedly have to write reports as part of your job or your studies. There are tricks to good technical writing. I’d like to describe some of them here, and list some sources of information that have proved helpful to us in our writing work. I’ve also included a list of recommended reading at the end of the editorial. Ask someone on the periphery of our field what the problem is with our prose, and he or she will probably say, “There's too much jargon.” Things like: 1/O, ASCII, byte, CPU, compiler, nonvolatile memory, BASIC, NAND gate, modem, macro, Pascal, floppy disk, Z80, 8080, 8086, 6809, 6502, 68000, Z8000, BCD, CP/M, Unix, Xenix, bootstrap, OS, DOS, DMA, CAI, CAD, CAM, vectored interrupt, monitor, RS-232C, S-100 bus, global variable, checksum, NOP, SWI, VOM, and so on, and so on. It’s a lexical maze for the uninitiated. But is jargon really our downfall? | think not. We need jargon in the same way that doctors and psychologists do — as a convenient form of shorthand. Programmers have traditionally wres- tled with the problem of fitting the most program into the least amount of memory space, so it's only natural that their everyday speech has been con- densed down to a sort of technical “alphabet soup.” Jargon isn’t intrinsically bad — it’s how you use it that counts. Knowing Your Audience: The Seesaw Effect Outside of grammar, syntax, and spelling (all of which I'll deal with later), there is the major consideration of your intended audience. Imagine your readers to be sitting at irregular intervals along a large seesaw. At one end are the most technically astute members of your audience; at the other, the interested novices, In the middle are people with varying degrees of knowledge in the subject you are writing about. Your job is to keep the seesaw as level as possible by attending to the various groups in proportion. If there are many novices involved, you must “hold up” their side by providing them with a lot of introductory material. But if you go too far in this direction, the experts will get bored, dismount, and leave you hanging with a partial au- dience. It’s a quandary, one that has no simple answer. Some topics are so technical that even the most intelligent novice will be left in your wake. You can’t understand the workings of a compiler, for instance, until you know a lot about computer languages in general. Some seesaws can’t be balanced despite the best intentions of the writer. It is the job of the writer to know this. Nevertheless, within limits, a lot can be “For reliable data storage, you can’t beat Shugart’s Minifloppy. “T sell systems my customers can depend on. That’ why most of the personal and small business computer systems sold here feature Minifloppy disk drives. I know from experience I can rely on the Minifloppy.” _ Since 1976 Shugart’s Minifloppy has been used by more small computer system manufacturers than any other drive. In fact, more than half-a-million Minifloppys ‘TM—Minifloppy is a trademark of Shugart Associates. have been installed. The Minifloppy looks small—but it stores a lot of data. 250 kilobytes on one side, or up to 500 kilo- bytes in the double-sided model. That's about 50 pages of printed information on a single-sided Minidiskette, and twice that on the double-sided version. You'll have plenty of storage capacity for your pro- grams, letters, forms, or ledger entries, And you find your data fast, too, because the Minifloppy is a random access device 99™M Raymond Schlitzer, Owner— Computerland, San Francisco that eliminates the need to search for your data serially as you must with a tape cassette unit. No matter what problem you're solving with your computer system, you can rely on Shugart’ Minifloppy for data storage. We're known as the Headstrong company for good reason. We're Headstrong about reliability, quality, and value. Ask your dealer. He knows us. Rely on the Headstrong Company. A\Shugart 475 Oakmead Parkway, Sunnyvale, California 94086 done to encourage those readers who are interested in your topic, but who may need some extra clarification. This leads me to the first of what I immodestly refer to as Morgan's Laws of Writing (not to be confused with DeMorgan’s Law): Morgan's Law #1: No Writer Ever Got Shot Down for Writing Too Clearly. How do you write clearly? A good first step is to buy a copy of The Elements of Style by Strunk and White. There is more wisdom contained in this slim volume than in many a three-pound guide to English Usage. Next, find some good technical writing and study it. I've included a bibliography of good technical books at the end of this editorial. We can learn a lesson from painters and musicians who take it for granted that good paintings and pieces of music by other artists should be carefully studied. Donald Knuth’s three-part series of books, The Art of Computer Programming, contains some of the best writing you're likely to find in our field — and he's funny, to boot! Another excellent writing tip comes from Peter Jacobi, a professor of journalism at the Medill School of Jour- nalism: Read your writing out loud. How does it sound? Is it awkward, circumlocutory, pedantic? If so, rewrite it, There's something about reading a piece out loud that lays bare its weaknesses. You can be clear without turning off the majority of your audience. See the accompanying text boxes for some Do's and Don't’s of clear writing, Morgan's Law #2: The Beginning Is Half the Thing. Actually, this is an old Roman saying I borrowed. The main point of it is that the first few paragraphs of an arti- cle are crucial to the rest of the text. The chances are you'll win or lose your readers at the beginning. Still, it’s the one part of an article that fledgling writers gloss over in their eagerness to write the main body of the text. One very good writer I know told me he spends up to half of his article-writing time creating the first few paragraphs! Morgan’s Law #3: Avoid the Penguin Syndrome. A famous story made the rounds a few years ago in- volving a publisher of children’s books. A copy of one of the company’s books about penguins appeared in the publisher's mailbox along with a letter from an eight- year-old girl that read, “Dear Sirs: I am returning your book, because it told me more about penguins than | wanted to know.” The moral? Tell your readers what they need to know, and no more. If you're zealous about a given topic, tell the reader how to get more information by including a comprehensive list of references. Don’t waste space. Morgan's Law # 4: Writing Is Nonlinear. Article ideas don’t come in an orderly sequence. Be prepared to jot down your ideas as they come, as writer John McPhee does. McPhee is blessed with a short-term memory that permits near-total recall. Even so, he writes 8 December 1980 © BYTE Publications Inc Circle 4 on inquiry card, ta PASCAL/Z”- Q.E.D. Ithaca Intersystems PASCAL/Z is the most powerful CP/M™ compatible Z-80™ Pascal compiler ever . . . and here’s why: PASCALIZ generates true Z-80 native code — ROMable and re-entrant — 5-10X faster than P-code interpreters; permits separate compilation; supports Direct File Access and variable length STRINGs; utilizes fast one-pass recursive descent organization; the macro-assembler generates relocatable object modules; and much, much more. Complete package includes compiler, macro-assembler, linkerfloader and source for the full library on one disk; with free copy of Jensen/Wirth book and complete documenta- tion. Only $395.00. {T'S DEMONSTRABLE! Don't just take our word for it. Ask for a demonstration of these features and more today at Computeriand® and other full-service computer stores. ithaca Intexsystems Inc., 1650 Hanshaw Road P.O. Box 91, Ithaca, N.Y. 14850. Phone (607) 257-0190 Compureriand i a registered tredemark of Computerand Corporation ind Z-80 are trademarks of Digital Research Corp and Zilog. inc respectively. PASCAUZ and InterSystems are trademarks al Ithaca intersystems Inc [looforMsys tens" Ithaca Intersystems Inc. Micros for bigger ideas. Outside of the garden you need a computer that can grow. For the average garden-variety home and hobby operation, a high quality personal computer is a real temptation. But let’s face it: in the world of business, engineering and scientific applications you need a system that can keep up with bigger ideas, Bigger ideas today mean the power and flexibility to move the micro up to and beyond the level of yesterday's More memory to hold bigger data bases. More lity to handle a variety of data entry devices. More programming and computing power for numbercrunching and applications development. And easy upgrade to 16 bit operation when you need it. Intersystems has that, and more. The power and flexibility of the versatile S-100 bus, with 20 slots of expandability for up to 16 individually-addressable DMA devices and up to 1 Megabyte of memory, fully accessible to all users via our unique memory management system. Plus reliable Intersystems design and manufacture, and the support of our PASCAL/Z’ lhe most powerful Z-80™ compiler ever. For really serious computing, our front panel provides a powerful diagnostic tool for debugging or development. Combined with a scope, it allows you to look al any location in the circuitry, set breakpoints, trigger and view one-shot events, and many other activities usually possible only with expensive logic analyzers. No wonder it’s fast becoming the tool of choice for repair technicians and custom hardware designers. Intersystems Series I is the most complete line of fully IEEE 696 compatible S-100 boards...easily upgradeable to our MPU 8000™ or other 16 bit S-100 CPU’s as they become available...so you're never locked out of rapid expansion, or locked into obsolescence, by dependency ona proprietary product line. So if you've left those garden-variety applications behind, come to Intersystems and get a system that will grow as big as your next idea. Get it from the people who know small computers...your Computerland store...or other fine full service computer dealers. Ithaca Intersystems Inc., 1650 Hanshaw Road P.O, Box 91, Ithaca, N.Y. 14850. Phone (607) 257-0190 TWX: 510 255 4346. Gircle 5 on inquiry card. motor Nyystennns” ithaca Intersystems | Micros for bigger ideas. his ideas on index cards every day and pins them to a bulletin board where he can mix and match them. The ac- tual writing of a piece might not occur until some time later. E B White recommends that writers use scissors and glue to cut and paste their efforts during the first-draft stage. Some of the more advanced word-processing pro- grams can help to do this. Another great writing aid is to use a data-base-handling program that allows you to cross-index ideas and file them away. Morgan’s Law #5: (otherwise known as the Three-Foot Rule): Don’t Write Anything Unless You Have a Dic- tionary and a Thesaurus Within Three Feet of You. I know I’m being a little strict here, but it's important. Unless the dictionary is within easy reach, you probably won't bother to use it, and you may make a spelling er- ror, Going without a thesaurus is a further way of handi- capping yourself. Bath these books are vital to every writer, and I needn’t tell you that the average level of spelling accuracy these days is low. The American Heritage Dictionary is a good all-round choice because of its excellent usage notes. There's nothing much I can say about improving gram- mar and syntax other than to suggest the reference books at the end of the editorial. The Careful Writer and Mrs. Thistlebottom's Hobgoblins by Theodore Bernstein both help to dispel many of the bugaboos that have haunted our language ever since the well-meaning Victorians got their hands on it. Bernstein correctly points out that it’s all right to occasionally split an infinitive, or to use a preposition to end a sentence with. William Sloane's The Craft of Writing, although primarily aimed at the fiction writer, contains a valuable chapter on nonfiction. It's a beautifully written book. Morgan's Law #6: Don't Be Afraid to Be Interesting. This may be the most important law of all. Involve your reader by being specific. Generalities make for dull reading. Use humor if you can carry if off. Otherwise, don’t! Add some personal observations and opinions. The reader will take them in stride. All of this leads to the general conclusion that you should write about what you know well. William Sloane says, “There are no uninteresting subjects, only unin- teresting writers.” In closing, I can think of no better quote than the following one from the same book (although Sloane is talking here about nonfiction books, the sentiment ap- plies equally well to technical articles): If a book has a beginning, it also has an end. Nonfic- tion develops by increment, builds on its own material, and ends when its material has been com- pletely exploited. If the book fulfills its contract with the reader, the end will complete the book by fulfilling the promises it made at the start. And if the people who read that book feel continuously that they are ad- ded to and believe, at the end, that there is more to them than there was before, the work of nonfiction has succeeded. The same can be said of fiction. In both cases, the contract between the writer and the reader has been kept. 10 December 1980 © BYTE Publications Inc Clear Writing: Some Do’s DO: (1) Tell your audience what you're going to talk about, (2) Taik about it, and (3) Tell them what you talked about. This old saw from your creative-writing class in high school is as valid as ever. Not observing it is a common failing of much technical writing today. DO: Include a theme sentence near the beginning of your writing that concisely sums up what you want to say in the piece. DO: Tell your story in miniature in the captions to figures, photos, tables, listings, and other illustrations. Your readers may not have time to read all of your ar- ticle: give them a quick summary and they'll thank you for it. Scientific American magazine does this sort of thing very well. DO: Spell out acronyms and abbreviations when they first appear in text. How many times have you been stopped cold by an unfamiliar abbreviation in the mid- dle of an interesting article? DO: Use verbs. Avoid adjectives and adverbs. A verb in an article title can add a lot of spice. (See Electronics magazine for good examples of verbs in titles.) Adjec- tives and adverbs, to paraphrase Robert Benchley, are the spinach of technical prose. Everybody says they're vital, but few of us would miss them if the majority of them suddenly disappeared tomorrow, John McPhee (perhaps the best nonfiction writer in the country) has written several books on technical subjects (such as The Curve of Binding Energy) that illustrate these principles better than a hundred paragraphs from me. DO: Break up your text into digestible chunks with subheadings. DO: Remember the questions you had when you were first learning a subject. Clear Writing: Some Don'ts DON'T: Use the passive voice as your primary voice. Many of us were taught to use the passive voice when writing technical reports and the like. But the passive voice lends an air of coldness and formality to writing — the sort of thing you'd expect in technical transac- tions, but not in an article that's designed to be read. For example, “I ran the program” is more personal than “The program was run.” Sometimes you need the passive voice for variety, but in general, own up: Say IL, me, my, we, us or you. DONT: Make your reader search for information in an article. If you have a list of items in text, perhaps they could be set off in a table. If you have a glossary in your article, tell the reader at the beginning. DONT: Use big words when small words will do. A good example is utilize, a word that can almost always be replaced with use. Another popular word that should be avoided is implement. Don’t implement when you can install, design, code, control, enable, connect, build, or operate; your readers will have a better idea of what you are doing. DON'T: Use a clever title for an article if it fails to convey the article's content. Imagine that your title is all that the reader has to go on in deciding whether or not to read your work, Text box continued on page 12 Circle 6 on inquiry card. —> Br Why not kill two birds with one stone? Tf you have an Apple* and you want to interface it with parallel and serial devices, we have a board for you that will do both. It's the AIO™ Serial Interface. ‘The RS-232 standard assures maximum compat- ibility with a variety of serial devices. For ex- ample, with the AIO you can connect your Apple” to a video terminal to get 80 characters per line instead of 40, a modem to use time-sharing services, or a printer for hard copy. The serial interface is software programmable, features three handshaking lines, and includes a rotary switch to select from Tetandard baud rates, On-board ti. SAA ware provides a powerful driver routine so you won't need to write any —x————EEE software to utilize the interface. Parallel Interface. ; ‘This interface can be used to connect your , = Apple® to a variety of parallel printers. The programmable I/O ports have enough lines to handle two printers simultaneously with handshaking control. The users manual includes a software listing for controlling parallel printers or, if you prefer, a par- \ allel driver routine is available in firm- ASST ERE ware as an option. And printing is only one application for this general purpose parallel interface. ae * Two boards in one. The AIO is the only board on the market that can interface the Apple to both serial and parallel devices. It can even do both at the same time. That's the kind of innovative design and solid value that's been going into SSM products since the beginning of personal computing. The AIO comes complete with serial PROM'’s, serial and parallel cables, and complete documentation including software listings. See the AIO at your local computer store or contact us for more information. ASW 4 7 17, 2190 Paragon Drive San Jose, California 95131 (408) 946-7400 nny People h, ave call ne questio, ‘alled with 1 We'll answer thors! fe AIO, ‘ LT A partial list ode be includ . Qume Spry, : Hi Prine S, pei ADRS 125, IDs DEC Sinwriven cue + Centronics 2 Doe, DTC 300, al age tine 1500, art Heathki F ‘ tegler theseaset! you wang Til firmware u ss al Patcher DusgPO"S With Pascal POM Or both a . T Our Of firmware op; iS erface? * PtiOn is available hi in S that . ac Sl me alone a js argir é card indentations any Vatiable page je oM® Provide: return, Auto-tine-feeg fri Variable @How asT: Carriag, i 01 intert, mine my Al canaee BY New pri : card? Print Interconnection, er to my Apple GT want ¢ DONT: Use it or other pronouns if the meaning is obscured. Vague pronoun references in an article slow the reader down. What does the it mean? Writing for BYTE If you'd like to write for BYTE, we offer the follow- ing guidelines: Knowing the reader: Over three-quarters of BYTE's readers are involved professionally with computers as programmers, systems analysts, engineers, or techni- cians, Most of them are dyed-in-the-wool hobbyists at heart and spend a lot of time with their systems. The majority have college degrees or fia at although we also have many student readers. Tey are interested in virtually every aspect of personal computing, in- cluding high-level languages, original hardware designs, reviews of software and hardware (we are especially interested in these), graphics, artificial in- telligence, using computers to contro! the home, games, robots, etc, etc, Although many of our articles contain highly technical information, we also encourage the submis- sion of lower-level tutorial articles to enable readers to brush up on the basics. BYTE's readers like to have fun with their systems, too — a fact that should not be overlooked. . © Take the time to write complete, descriptive cap- * color slides to color prints. DEALERS...OEM USERS. Call on Monday... your North Star computer will be Thursday. WHOLESALE PRICES AVAILABLE. GBC maintains ready stack on the follow- ing products and software: * North Star * Centronics * Perkin-Elmer «Epson * NEC Spinwriter * Turnkay North Star Business Software (609) 424-0465 Avent 6 B00: cherry Hl Hill, New Jersey 0800 12 December 1980 © BYTE Publications tne Circle 7 on inquiry card. Form of the Submitted Article @ All submissions should be double-spaced and typewritten on 81% by 11 inch paper, with the narrow dimension vertical. Double-spacing is important, since proofreader's marks and other ations must be made to the manuscripts. tions for all figures, tables, listings, and photos. ®@ Schematic diagrams should be neatly drawn, using the schematics in BYTE as a guide. Note that we prefer @ certain type of connector designation, and that power connections to integrated circuits are usually listed in a separate power-wiring table rather than be- ing included in the schematic. The direction of flow in a flowchart is assumed to be downward and to the right, No directional arrows should be.used unless the flow is contrary to the, aforementioned directions. ‘Again, see the magazine for examples. @ We prefer not to typeset listings, but rather to photograph them for the magazine in order to eliminate the possibility of typographical errors. Because of this, we ask authors to submit listings printed on white paper with a dark ribbon (preferably new). ©@ Photographs can be either color or black and white, but should be as sharp as possible. We prefer @ All submissions should be accompanied by a stamped, self-addressed envelope with sufficient postage affixed. We acknowledge all manuscripts upon arrival, and make a final determination within 8 to 12 weeks. Reference Books Rathbone, Robert R. Communicating Technical Infor- mation. Reading MA: Addison-Wesley, 1972. A good source of information about technical writing. Ralston, A, and Meek, C, eds, Encyclopedia of Com- puter Science. New York: Petrocelli/Charter, 1976. Although this book is oriented more toward large computers, it contains a wealth of information about high-level languages, assembly language, data process- ing, and hundreds of other topics, all presented in lucid fashion. Every serious computer science library should have a copy. Bernstein, Theodore M. The Careful Writer: A Modern Guide to English Usage. New York: Atheneum Press, 1977. Highly recommended, along with the author's other book, Mrs. Thistlebottom’'s Hobgoblins, Burton, Philip E. A Dictionary of Microcomputing, New York: Garland Publishing Company, 1976. Still the best dictionary in the microcomputing field. Turner, R P. Technical Writer's and Editor's Stylebook. New York: Howard W Sams and Com- pany, 1964. Todd, Alden. Finding Facts Fast. Berkeley'CA: Ten Editorial continued on page 294 Circle 8 on inquiry card. —> Edison had over 1,800 patents in his name, but you can be just as inventive with an Apple. Apple is the company with the brightest ideas in hardware and software and the best support — so you can be as creative with a personal computer system as Edison was with the incandescent bulb. How Apple grows with you. With Apple's reliable product family, the possibilities of creating your own system are endless. Have expansion capa- bilities of 4 or 8 accessory slots with your choice of system. Expand memory to 64K bytes or 128K bytes, Add an Ato D conversion board. Plug into time sharing, news and electronic mail services. Use an IEEE 488 bus to monitor lab instruments. Add 4 or 6 disk drives — the 54s" 143K bytes, high-speed, low-cost drive that’s the most popular on the market. Apple speaks many languages. Since more than 100 companies create software for Apple, you’ll have the most extensive library in the personal computer world. Want to write your own programs? Apple is fluent in BASIC, Pascal, FORTRAN, PILOT and 6502 assembly language. There's even a series of utility programs called the DOS Tool Kit that not only lets you design high-resolution graphic displays, but lets you work wonders with creative animation. More illuminating experiences in store. You won't want to miss all the Apple products being introduced at your computer store all the time. Don’t let é history pass you by, Visit your nearest Mem Apple dealer or call 800-538-9696. In California, 800-662-9238. Or write: Wem “pple Computer, 10260 Bandley Drive, Se Cupertino, CA 95014. apple computer inc. Letiers Heath Faces Horizon John Dye remarked in his letter (August 1980 BYTE, page 18) that he cannot run his Heathkit H-14 printer with a North Star Horizon at any data BUSY from the H-14. transfer rate over 110 bps (bits per se- niet which allows you to obtain a cond). A si tion of the signal on the printer's connector Horizon , aS by Don pin 4. This pin translates to pin 15, Baker, will allow it to recognize the T have assembled three H-14s and in- terfaced them with Horizon systems at 4800 bps with no problems, Heathkit supplies a modification-instruction pam- After you play the Temple of Apshai, you can play Sticks and Stones for free. Within the 200 rooms and —_for no extra charge. In fact, if catacombs of the Temple of you're not satisfied with the Apshal, untold treasures await “Temple of Apshai,” you can you —the hero. All you have —_—return it within 10 days and still fo do Is elude, outsmartand — keep “Sticks & Stones!“ outwit the beasts, monsters But don’t walt, this special and demons lurking in the Offer Is limited. (We'll also send dark labyrinth. Spend minutes you a catalog outlining our or hours on this role-playing other exciting com- fantasy — the boldest computer game In our Dunjonquest™ series. Now, when you order the “Temple of Apshai,” you get the “Sticks & Stones” board game Automated Simulations, Department BY P.O, Box 4247, 1888 Leghorn Street puter games). Mountain View, Catitomia 84040 Please sand me the “Temple ot Apshai for: | Cassette ($24.95) Disk ($28.95) | TRS-B0 0 16K, Levelt CO 32k TRSDOS ‘APPLE Not available 48K Applesoft In ROM PET 032k Nol avalloble (Add $1.00 shipping and handling charge; pius 6% or 6%% tox (or Collfomnia residents.) 1 Name. Address ity, State, Zip. | C1 Check enclosed. Chorgeto: 1 VISA 11 MasterCard | amount $ . Expiration date 1 Or charge by phone: (800) 824-7888, operaior 461. in Callfomia: (800) 852-7777, operaior 861, Mf you prefer, calt these numbers for a list of the computer slores near you. D 14 December 1980 © BYTE Publications Inc Circle 9 on inquiry card. DB:XMIT CLK (DCE), on the Horizon motherboard, To accomplish the hand- shaking, jumper the right configuration- header at location 4D as follows: Connect pin 2 to pin 16 Connect pin 4 to pin 14 Connect pin 5 to pin 11 Connect pin 7 to pin 8 Connect pin 9 to pin 10 and Connect pin 12 to pin 12 of the right special-clock header at loca- tion 2C. David M Koehler 306 Timber Trl Lafayette IN 47905 The APL Plot I was very pleased to see BYTE's August 1980 FORTH issue, since | am working part-time with FORTH doing a computer-aided design package to be used with the fine Mauro Engineering Proac plotter. Incidentally, the new product announcement for this plotter in the August 1980 BYTE (page 249) refer- red erroneously to the unit as a printer in the heading. The self-replicating programs in “Pro- gramming Quickies” (see “Self- Reproducing Programs,” by Burger, Brill, and Machi, August 1980 BYTE, page 72) are a challenge that APLers cannot pass up. I have a 22-character line of APL that reproduces itself when executed, which was published a few years ago in APL News, a free publica- tion of APL Press (not to be confused with Personal APL News, my publica- tion, which is now part of the APL Market Newsletter from Southwater Corporation}, Anyone who is interested should contact Eugene McDonnell of I P Sharp in Palo Alto, California. If we take the character string: APPL Smt ee) 11 Cease Tip tt Est and then print it and execute it, we get: a 14#23piip **1423p4ip tt! 2A 1#23p110'''1423011p tt! The key to this line is the fact that the reshape function wraps around to the be; of the right argument. I hope that the following makes it clear what is happening: Tehas2sp tip tt! a#23piip! 11p''"1423p110""* "1423pdip'* Gircle 10 on inquiry card. —— TRS-80* Model I Computer Owners .. . Store Up to 350 Kbytes on a 5” Disk “e f ALE, oe £4 wi om v The DOUBLER”. It packs almost twice the data on a disk track as your single-density system. Depending on the type of drive, you can store up to four times more data on one side of a minidiskette than you can store using a standard Model I mini-disk drive. ® The DOUBLER™ reads, writes and Ganareetmer single: or dou- ble-density minidisketies. @ Propriet: to continue torn *TRSDOS? NEW. DOS}, Percom OS-80™ or other an ile-density aha without any changes to software = hardware. Switch to double- density operation at any conve- nient time. ® Includes JAA e TRSDOS* compatible double- density disk operating system. Mini-Disk Systems More Nohertlapity = For Percom, the ind leader. One-, two- ¢ three-drive confic re tions in either 40- or 77- heck format. Fully burned-in. Fi ‘only rademark “ada of enya She rion tick ha no atop te Pao Dts Compan. 2 trademask of Apparat e CONVERT utility, on DBLDOS™ minidiskette, converts and programs from single- to files or double- to sin- | gle-density. ® The DOUBLER™ circuit card includes high performance data ‘ator, write precom- circuits for reliable rc operations — even with drives. Installation — The t simply plugs into the BouBEER simply luge into the | (5 pemcom piscount #91 1 cone 1 I toward ' | The Purchase of a | I ™ 1 i ! 1 Oe ies oo TEE Lam HEC Ra Se pansion Interface, requiring no evopping or trace cutting. n> sion Interface disk controller may be completely restored to original ration by si removing the DOUBLER™ pede arama the original disk controller chip. ‘ Works with standard 35-, 40-, 77- and 80-track mini-disk drives rated for double-density operation. @ Introductory price, including DBLDOS™ and format conversion Buds Gate saree ee 95. even greater savings. Call toll-free, 1-800-527-1592, for the address of your nearest authorized Per- com dealer, or to order directly from Per- com. SRW Winey CARLA TOS 202 (214) 272.3421 PRICES AND SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE, + PRICES DO NOT INCLUDE SHIPPING AND HANDLING CHARGES. 23plip't*1+2I3p1ip*'* "2423p 11p''421423paip ttt This is much shorter and also much simpler in conception than the other self- replicating programs given. It is not, however, a defined function, but an ex- pression. I don’t think it would be dif- ficult to write an APL function that would produce its own visual represen- tation, even without using the visual representation function which makes the question trivial: URSHYSELP RVR "MYSELF! a This function returns its character form as a value, and only prints by default if that value is not assigned to a variable; the expression given earlier also yields a value and not just printing. Only LISP can improve on that, by returning a function as its value, rather than a character vector (character string to the rest of you). Other variants of this amusement have been worked out in APL before. Try creating two expressions, each of which gives the other as its value or its printed result, or a cycle of three or more. at Mokurai Cherlin Director, Micro Systems Development APL Business Consultants Inc APL Computer Language Specialists POB 1131 Mt Shasta CA 96067 Thlef-Reproduthing Programth We are rather amazed and amused by the “Self-Reproducing Programs” (see the “Programming Quickie,” by Burger, Brill, and Machi, August 1980 BYTE, page 72). We were amazed by the elegance of the “optimal” C program presented (especially given C’s notable lack of expressive wer), and amused by the proposed. solution (which, by the way, won't work. What was pro- posed will not evaluate to a function — it needs an enclosing DEFUN or DEFINE). Consider the problem of creating an expression which evaluates to itself, A microsecond’s thought usually yields a constant, usually 1. Indeed, any friendly APL or LISP interpreter would be more than happy to return 1 when 1 is typed to it, However, many people would claim that 1 is data, and not a program. For the sake of this letter, we will pay go “up” a level in our analysis. The canonical “program” in the lambda calculus which reduces to itself is: homage to this unfounded prejudice, and PUT TIME AND BSR CONTROL IN YOUR APPLE II THUNDERCLOCK PLUS AN INTERFACE FOR THE BSR X-10 “Control AC outlets with your BSR Command Console and APPLE II «All 22 BSR commands at your pro- gram’s lingertips * Up to 128 separate dim/bright levets * THUNDERWARE’S Scheduler soft- ware will control AC outlets in the background, while you run another program in the foreground BOTH FEATURES ON ONE CARO A REAL-TIME CLOCK/CALENDAR » Provides month, date, day-of-waek, hour, minute, and second * Software selectable time formats: 24 hour or AM/PM ASCII string, or as numeric values = Provides interrupts which can be en- abled or disabled under software con- trol * On board battery allows accurate time- keaping for up to 2 years even with your APPLE turned off » On-board firmware makes the THUNDERCLOCK PLUS" exceptionally easy to use ‘= Read or set time, control interrupts, and send BSR commands with simple BASIC “INPUT’ and ‘PRINT’ statements = Completely APPLE {1 compatibls: (NT and FP BASIC or PASCAL with Unit support = Special introductory prices end Jan 15, 1987 _ THUNDERCLOCK PLUS Clock, BSR interface, and THUNDERWARE SCHEOULE! Diskette with Scheduler, ax: and Scheduler manual PASCAL SOFTWARE. 81 Diskette with PASCAL Unit for “Clock a BSR interface TO ORDER TOLL FREE (VISA/MC) CALL: 800-227-6204 Ext, 307 (Outside California} 80 31 Ext. 307 (California Only) ta add 6 eal ta, 10 isa teaddemark of BSA (USA) LTD. 16 December 1980 © BYTE Publications Ine aside SEE YOUR DEALER OR WRITE FOR INFORMATION: THUNDERWARE INCORPORATED P.O, Box 13322, Oakland, CA 94661 APPLE It ise trademark of APPLE COMPUTER, INC. Circle 11 on Inquiry card. Ax XX AX XX): The first (x20) is the “p d the py Dee ae pee gram. When this “program” is “executed” the formal parameter x is bound to (\y.xx) parameter of the pro- gram (x), then x is concatenated with itself once (this is what xx means), and then this value is returned. (You may find it instructive to compare this with the “optimal” C program.) We shall try to emulate this in LISP. The first attempt yields: ((lambda (x) (list x x))(ambda (x) {list x x))), however, this fails because the data part will get evaluated. We can try: (lambda (x) (list x x))"(lambda (x) (list x x))) but this only yields: (Qambda (x) (list x x))(lambda (x) (list x x! which is missing the quote mark. An in- teresting hack is to change the way lambda evaluates by executing (macro lambda form (list ‘quote form)). The first attempt above will now work because when (lambda (x) (list x x)) is evaluated it will return a copy of itself, which is what we want. However, there are those that would claim this is cheating because we have implicitly changed the behavior of the evaluator. We will admit this objection and con- tinue with our analysis. After much mushing around trying to get the quote mark back in we stumble upon: {(LAMBDA (LAMBDA)(LIST(LIST ‘LAMBDA (LAMBDA) LAMBDA\(LIST ‘QUOTE LAMBDA))) “LIST (LIST ‘LAMBDA (LAMBDA) ) LAMBDAMLIST'QUOTE LAMBDA))) which does what we want. Note that this uses no PROG, SETQ's or REPLAC y's. Also note that the lambda variable need not be named lambda, this is merely a hack. It is trivial to make a program out of this expression by throwing up the necessary DEFUN’s: (DEFUN PRINTME() ((LAMBDA (LAMBDA)(LIST "‘DEFUN ‘PRINTME()(LIST(LIST LAMBDA. (LAMBDA) LAMBDA) (LIST ‘QUOTE LAMBDA)))) “LIST ‘DEFUN ‘PRINTME'(X(LIST(LIST ‘LAMBDA Circle 12 on inquiry card, —> SAN JOSE, CALIFORNIA September 5.6.7 LONDON. ENGLAND september 4.5.6 1980 1980 captures, announcesertors. Plays at ten levels ot * difficulty. Apfalyzes over 3,000,000 moves —it's faster and smarter than ever, Speaks English, Spanish, French ar German language: « Chess Clock tells time remaining, elapsed time, time used per move. The same engineers who helped win the “First World Microcomputer Chess Championship” under the auspices of the World Chess Federation on Sep- tember 4, 5, and 6, 1980 in London, England—five straight wins with no loss or draw — and the “First Official North American Microcomputer Chess Cham- pionship” on September 5, 6, and 7, 1980 in San Jose, California—four straight wins without a loss or draw — are proud to announce Fidelity’s newest chess product... + Duplicates 64 of the world’s greatest games — you play against the Master. + Plays 64 book openings, average 15 moves into the game. + Many other features include: Problem Mode, Mate-in-Two solutions, change sides in mid-game, and much more. For the beginner or serious player. Available in fine stores everywhere. Spanish, French or German optional. The world’s largest manulacturer of sell-contained. microprocessor based. board games. Quality made in US A 1G Fweury ELECTRONICS, LID. 12.00... ww sss ss, 10x09 09 read cards... economically! The new HEI Model 121-4 card reader handles marked and punched cards interchangably, MO RMR including many colors of pen or Pe hae pencil. Absolutely no operator dy adjustment required. Includes a number of switch-selectable features for application tailoring without extra cost. © Reads strobe marks right or left, or self-clocking on both 80 column punch and mark-sense cards. @ RS-232 ASCII output (with Hollerith to ASCII conversion if necessary), or parallel TTL output. © Six in-per-sec. card feedthru, or auto return to the front after read. A built-in self test feature checks all 13 channels with a diagnostic card. The Model 121-4 operates on 50/60 CPS. Specify voltage as either 110 or 230 VAC. The Model 121-4 is the most flexible and capable hand-fed card reader on the market at any price, and the priceis right. You'll find it to be ideal for a variety of inventory control and data collection tasks. Call or write for more information on the latest optoelectronic solution from HEI. The Optoelectronic Specialists fi] HElinc. Jonathan Industrial Center ¢ Chaska, MN 55318 © 612/448-3510 Circle 13 on Inquiry card. ae e fe , ate te, “ (LAMBDA) LAMBDA) (LIST ‘QUOTE LAMBDA))))) However, neither of these two solu- tions would be written that way in a modern LISP (eg: MacLISP or Lisp- MachineLISP, instead using the back- quote facility they would be written: ((lambda (x) ‘(,x ‘.x)) ‘(lambda (x) Ux’) and: (DEFUN PRINTME() (LAMBDA (X) .@X',X))) “(DEFUN PRINTME ()((LAMBDA {X) “.@X,X))))) The real way it wouldbe written in MacLISP is (DEFUN PRINTME () (GRINDEF PRINTME)). This whole ex- ercise really isn’t sey interesting in LISP because this sort of thing is done routinely. Routines are constantly being consed up by other routines, and macros which write their own macros are be- coming a standard tool. LISP doesn’t discriminate against something just because it is code. Daniel Weise NE43-838 MIT Laboratory for Computer Science 545 Technology Sq Cambridge MA 02139 Leedex / Sup'R’ Terminai Incompatibility Any BYTE reader who owns an Apple II system and is considering expanding to 80 columns may be interested in my experience with the Leedex monitor and the Sup’R’ Terminal RF (radio-frequen- cy) modulator board. While the Leedex monitor is an excellent value and per- forms well with the standard 40-column Apple II, I found it impossible to get a clear display while using it in conjunc- tion with the Sup’R’ Terminal board, Repeated efforts at adjusting both the board and the monitor failed to produce a legible display. The only solution pro- ved to be using another monitor, namely a Hitachi. Sunil Subbakrishna Shakti Systems Wilmette IL 60091 Bar-Code Reader as Light Pen? Before reading Car] Helmers's editorial “Bar Codes, Revisited . . . ” (April 1980 BYTE, page 6) on the Hewlett-Packard HEDS-3000 bar-code data-entry wand, I considered the possibility of buying a light pen for my Apple II. Afterwards, 1 couldn’t see buying two pieces of equip- ment when one might do both jobs. Circle 14 on inquiry card. — Mountain Computer makes more peripherals for | the Apple Computer than Anybody. and... aplace to put them Intelligent Home Controller for lights and appliances. Real-time schedules and energy conservation, Complete applications software package. Home security with random scheduler. Power usage accounting package for home energy cost control. No wiring required. Real-time and date information. Interrupts permit Foreground/Backgtound operation of two programs simultaneously. Batlery back-up. Crystal-controlled for + .001% accuracy, Onboard ROM lor easy access from BASICs. Supports PASCAL. Time from one millisecond to one year, Input/Output Speech Digitizer. Permits talking programs. 1/O capability allows interactive programs wilh speech-prompted inpuls. Use output for speech directed activities in business systems, announcements in acontrol- room, or sound effects in entertainment programs. Easy to use because input a8 well as output is under user control with special software operating system Program your own EPROMS. Greate your own firmware. Programs 2K, 2716 SV EPROMs. Disk saltware package provides easy EPROM programming, EPROMs are verified after BURN. RUN your programs from on-board sockel or instal! them on ROMPLUS + More power lor your system through firmware. Six sockets accept 2716 EPROMs or ROM equivalents. Six or any com- bination can be used at once. Scratch-pad RAM and two TTL connectors. Special 2K ROMs available for powertul system enhancement: Keyboard Filter ROM—COPYROM—Others coming soon. Sophistication previously available only. on experimental mini and mainframe com- puter syothesizers. Digital instrumental music synthesizer system 16 voices in stereo. Instrument delinitions simulate the ‘sound of rea} instruments—and more. Fully programmable wavelorms. Envelope Con- trol. Composition system—sheet music input using standard music notation Chords and multi-part scoring up to 16 voices. A true instrument that anyone with an Apple can play 16 channels analog to digital input. 16 channels digital to analog output. Eight bit resolution. Super-last 9 sec. conversion time. Monitor and ‘outpul to the real world, All on one card. By popular demand! Eight more stots for your Appie. Attractive sturdy enclosure. Its own heavy duty power supply. Easy to use Address cards in Expansion Chassis the same way as in your Apple. Only one additional command to spacily in Apple or in Expansion Chassis. Compatible with all Apple peripherals. At last! An intelligent, high-quality device tor data entry from user-marked cards, Implement BASIC programming, examination scoring, inventory maintenance and other applications requiring off-line data preparation for batch entry Jater. Gonnects to any computer having RS-232 interface. Software and cards are available for jobs in business, science and education. MOUNTAIN COMPUTER has the most compre- hensive line of Apple peripherals available. Anywere From anybody. We know the Apple inside and out and are committed to providing. the most innovative and unique products to expand and enhance its capabilities and use Alter ail, we were the first company to make an Apple peripheral—-except Apple Computer. Available at Apple Dealers worldwide, 300 Harvey West Blvd., Santa Cruz, CA 95060 (408) 429-8600 TWX 910 598-4504 Apple is 8 trademark ol Apple Computer tnc. That is, can the wand be altered so as to become a light pen? John Gibbs If you don’t activate the infrared LED (light-emitting diode) in the HEDS-3000, you can certainly sense light coming into the wand from an external source, such as the video display's CRT (cathode-ray tube). There might be problems in matching the wave length of the light from the CRT to the spectral sensitivity of the infrared phototransistor in the wand...CH Telecommunication Options software, As part of this endeavor, we are compiling a directory of all software that runs on MDOS or Micropolis BASIC without requiring a second operating system (such as CP/M). I woul perecate suppliers of such soft- ming me of their products. Ot course we are also always in- terested in new members. Membership is $12 per year for twelve monthly newsletters. Buzz Rudow Micropolis Users Group T enjoyed Carl Helmers’s June editorial very much. (See “The Grass Roots Elec- tronic Post Office, or, How Electronic (and Private) Mail Is Already Here,” June 1980 BYTE, pages 6 thru 10.) The prospect of using my terminal for rapid and inexpensive communication is very exciting. The costs you mention for sending computer messages using voice telephone lines can be greatly reduced by taking advantage of the digital communication provided by Telenet or Tymnet. This is easily done by means of The Source or MicroNet information services. Elec- tronic mail can be sent with The Source for $8.50 per hour of connection time counting both send and receive time dur- ing e” hours, but not counting the initia charge. Similarly, MicroNet charges $10 per hour (for oth send and receive) and has a lower initial charge. In addition, both systems permit users to chat on-line with other users through their respective terminals. Robert W Hosken Avatar Exports 21515 Hawthorne Blvd #432 Torrence CA 90503 According to my table of telephone rates, the cost for a one-hour telephone call from New Hampshire to California during the 60% discount time period (which Carl Helmers used as an exam- ple) would be $9.65. The cost would be less, of course, for a call over a shorter distance. Using The Source or MicroNet has the benefit that the two correspondents do not Le i send a ree ee: and opens the ibility for reali repent g roew nore munication . Info on Micropolis Software Wanted The Micropolis Users Group (MUG) is an association whose desire is maximiz- ing the use of the Micropolis-supplied 20 December 1980 © BYTE Publications Inc 6809 Time-Sharing Don Kinzer's article in the June 1980 BYTE ("A Time-Sharing/Multi-User Subsystem for Microprocessors,” page 122) describes how a sixteen-user time- sharing system can be implemented. The system, based on a 6800 microprocessor, uses a minimum of pardvesre and soft- ware. However, the new 6809 pro- cessor, even less hardware and software is required. The first savings of hardware occurs at power-up/reset. Most processors, in- cluding the 6800, accept a nonmaskable interrupt (NMI) at any time—even at reset. Obviously, if an NMI occurs before the stack is initialized correctly, the program will bomb. The problem is usually solved by adding a special circuit that disables all interrupts until the pro- cessor is properly initialized (as shown in figure 4 of Kinzer's article). On the 6809, the NMI is blocked until the first load of the system stack pointer (SP). Thus, no special reset circuitry is needed. After initialization is complete, the stack pointer is loaded to enable the NMI. Note that most interrupt timers must still be initialized; when using the 6809, simply use the RESET signal to clear the timer to a known state. The 6809 allows direct addressing anywhere in the memory map. By use of a direct page (DP) register, the 64 K-byte addressing range is divided in- to 256 pages. In a time-sharing environ- ment, the DP register could be loaded with a different value for each user, resulting in each user accessing a dif- ferent 256 bytes of temporary storage. An alternate method of implementing a time-sharing/ multi-user system is with the 6829 memory-management unit (MMU). The MMU expands the address space of the 6809 from 64 K bytes to 2 megabytes. Each MMU can handle four concurrent tasks; the address space of each task can be fully protected from other tasks. In addition, a total of eight MMUs can be used in a system, Letters continued on page 298 ‘Circle 15 on inquiry card. — A growin fine of fonls to external ‘on-board ROM, and much more. ‘7 720A Porailel interiace, Two bi-directional 8-bit I/O ports will connect your Apple to a variety of parallel devices, bapa a paper tape Seat current relays, extemal on/off i, programmable inter. ‘tote expats DMA heey culo 78118 Arkhmetic Processor, Interfaces with 1A Asynchronous Serial interface. Conform ing to RS282C A Cav 1978 standard, ts card will drive a variety of serial devices such a8 Keble sper hensi tethie, ‘communicate with any standard RS-232 device, including other: computers al hand-shaking, and fully compatible with Apple PASCAL! ‘TATOA SX BCD A/D Converter, Converts a DC voltage to a BCD number for computerized ‘monitoring and analysis. Typical inputs include DC inputs from temperature or pressure transducers. Single channel A/D, 400 ms Per conversion. 74904 PIB IEEE 488 Interface. A true imple- mentation of the IEEE 488 standard—the TI14A PROM Module. Permits the addition to or replacement of Apple II firmware without ptr domme chelate b atind be on-board enable/disable toggle switch. 7500 A Wire Wrap Boord, For prototyping your own designs. ‘TSIOA Solder Boord, TSQOA Extender Board. 7O16A 16K Dynamic Memery Ag6-On, Watch this space for new CCS products for the Apple. We've got some real surprises in the works, To find out more about the CCS product line, visit your local computer retailer. The CCS. product line is available at over 250 locations nationally, including most that carry the Apple. ‘Or circle the reader service number on this ad. gle 0 Plus, and Ay trademarks et be Rope porate: Pera CCS makes the difference. We see the Apple rently. t f thi r don high-speed math functions, and fast, high resolution graph- way 0 ge | ngs ie. ics, And tools to connect the Apple to lab test equipment like function generators or plotters. Apple has built a great computer. We at CCS have And we have tools to connect the Apple to the outside built a great line of peripherals and components toexpand _ world, including A/D converters and interval timers with the Apple. To do almost anything you want to get done external interface. with a computer. We make components for the $-100 bus, the PET, and If you warit to do business with an Apple, we've got the TRS-80, too. We built our products to deliver hard- tools to connect the Apple to standard business printers and nosed value to the OEM, and to the inventor who knows the terminals. Or to modems, for communications over tele- best, at prices that are unbeaten. phone lines, with other computers, even with other Apples. To find out how much computer your Apple II can be, If you want to apply your: Apple to engineering, scien- _ see things our way. Because for serious users with serious tific, or graphic projects, we've got tools for high-powered, —_ uses for the Apple, we've got the tools. California Computer Systems — | 250 Caribbean Sunnyvale,CA94086 (408) 734-5811 Your vehicle for com The Challenger 8P DF. The general purpose microcomputer was first introduced as a computer for hobbyists and experimenters. However, as the industry has grown, microcomputers have become specialized for personal use or for smail business use. There is virtually no computer for the serious experi- menter with one important exception, the Ohio Scientific Challenger 8P. The C8P is unique in that it incor- porates the features of state-of-the- art personal computers, with the memory and disk storage capacity of business computers, along with the "mainframe" bus architecture and open ended expansion capability of industrial control computers. Personal Computer Features The C8P DF's specs beat all personal computers hands down. It executes instructions two to three times faster, and displays more alphabetic characters on its screen than other models. It has upper and lower case and graphics in 16 colors. The C8P's Standard \/O capabilities are far more extensive than any other com- puter, with joystick and keypad inter- faces, sound output, an 8-bit D/A converter, 16 parallel I/O lines, modem and printer interfaces, AC remote control and security monitor interfaces and a universal acces- sory port that accepts a prom blaster, 12-bit analog I/O module, solderless prototyping board and more, Ohio Scientific offers a large library of personal applications programs, including exciting action games such as Invaders and Star Trek, sports simulations, games of logic and educational games, personal applications such as biorhythms, calorie counter, home programs such as checking and savings account balancers and a home budgeter just to name a few. Anew Plot BASIC makes elaborate anima- tions easy, and music composition program allows you to play complex multi-part music through the com- puters DAC. At the systems level the machine comes standard with OS-65D, an ad- vanced disk operating system with Microsoft BASIC and an interactive Assembler Editor. Optional software includes UCSD PASCAL and FORTRAN and an Information Management System (OS-MDMS) Dozens of independent software suppliers now also offer personal programs for the C8P. puter explorations. Business Computer Features The C8P DF utilizes dual 8” floppy disk drives which store up to eight times as much information as per- sonal computer mini-floppies, and an available double-sided option expands capacity to 1.2 megabytes of on-line storage. The C8P DF is compatible with Ohio Scientific’s business computer software, in- cluding OS-65U an advanced oper- ating system, and an Information Management System (OS-DMS) with supplementary inventory, account- ing, A/R-A/P, payroll, purchasing, estimation, educational grading and financial modeling packages. The system also supports word process- ing (WP-3) and a fully integrated small business accounting system (OS-AMCAP V1.6). The C8P DF’s standard modem and printer ports accept high-speed matrix printers and word-processing printers directly. Home Control and (Industrial Control The C8P DF has the most advanced home monitoring and control capa- bilities ever offered in a computer system. It incorporates a real time clock and a unique FOREGROUND/ BACKGROUND operating system which allows the computer to function with normal BASIC pro- grams, at the same time it is monitoring external devices. The C8P DF comes standard with an AC remote control interface, which allows it to control a wide range of AC appliances and lights remotely, without wiring, and an interface for home security systems which moni- tors fire, intrusion, car theft, water levels and freezer temperature, all without messy wiring. In addition, the C8P DF can accept Ohio Scien- tific's Votrax voice I/O board and/or Ohio Scientific’s new universal telephone interface (UTI). The tele- phone interface connects the com- puter to any telephone line, The computer system is able to answer calls, initiate catis and communicate via touch-tone signals, voice output or 300 baud modem signals. It can accept and decode touch-tone signals, 300 baud modem signals and record incoming voice messages. These features collec- tively give the C8P DF capabilities to monitor and control home functions with almost human-like capabilities. For process control applications, a battery back up calendar clock with automatic computer restart capabili- ties is available. Ohio Scientific’s unique accessory ports allow the connection of a nearly unlimited number of 48 line parallel !/O cards and 12-bit high speed instrumenta- tion quality analog I/O modules to the computer by inexpensive 16-pin ribbon cables. Exploring New Frontiers Ohio Scientific's vocalizer software processes normal BASIC print state- ments with conventional spellings and speaks them clearly in real-time on computers equipped with the UTI (CA-15B or CA-14A). This voice out- put capability, combined with the C8P’s remote control, remote sens- ing, telephone interface capabilities and reasonable cost open up new frontiers for computer applications. Documentation The C8P DF is not a beginner's com- puter and doesn’t come with begin- ner's documentation. However, Ohio Scientific does offer detailed documentation on the computer which is meaningful for experts, including a Howard Sams produced hardware service manual that in- cludes detailed block diagrams, schematics, parts placement dia- grams and parts lists. Ohio Scientific is now also offering fully documented Source Code in machine readable form for OS-65D, the Challenger 8P’s operating system allowing experimenters and industrial users to customize the system to their specific applications. What's Next? Ohio Scientific is working ona speech recognizer to complement the UTI system, with a several hun- dred word vocabulary. The company is also developing an 8 megabyte low-cost, add-on hard disk for use in conjunction with natural language Parsing to further advance the state- of-the-art in small computers. The modular bus architecture of the C8P assures system owners of being able to make use of these new developments as they become available just as the owner of a 1976 vintage Challenger can directly plug in voice output, the UTI and other current state-of-the-art OSI! products. The C8P DF with dual 8” floppies, BASIC and two operating systems costs about $3000, only slightly more than you would pay for a dual mini-floppy equipped personal com- puter with only a fraction of the capabilities of the CaP. For more information and the name of the dealer nearest you, call 1-800-321-6850 toll free. 1933 SOUTH CHILLICOTHE ROAD AURORA, OH 44202 ¢ (216) 831-5600 Circle 16 on inquiry card. Multimachine Games Ken Wasserman and Tim Stryker Mach 2 Software 96 Hammersmith Apts Danbury CT 06810 There you are, staring into a poor dumb tube, spend- ing hours trying to wheedle, cajole, flatter and coax your machine into coughing up a few more points, or maybe into reluctantly admitting every now and then: “YOU WINII(bell)(bell)ttI” How much satisfaction is there in that, really? How much challenge? So you beat the com- puter. So what? So the computer beat you. Who cares? Do you ever long for a scenario something like the following?. . . . Tonight will be the final, deciding match of the battle series—the winner will have won the regional computer- club title and will be eligible for the national playoffs next month in San Diego. As you and your worthy opponent, both dressed in black, enter the room, a hush falls over the gathered assembly. You approach your respective consoles, and, at a prearranged signal from the presiding judge, the game begins. The screen before you contains a wealth of information about the status and positioning of your various forces. You have two “windows” onto the field of play, one centered on your base, the other on your current tank. You see no sign of your opponent or his base in either window, for pa field of play is very large: you know that he is out there somewhere, but, as the game begins, you have no idea where. As you begin to move your tank out of your base, you find that it stays centered in its own window, thereby making previously unseen portions of the field visible to you, while, from the point of view of your base (which is immobile) your tank appears to move away from win- dow center until shortly it disappears off the edge. Quick- ly reconnoitering your base perimeter, you begin to lay n mines to protect it from invasion. (These mines are visible to you but not to your opponent, to whom a Cassettes containing Flash Attack for the PET, at $15 each, and kits containing all the hardware needed to run Flash Attack and other games on the PET, in- cluding CB2 sound, at $15 each, are available from: Mach 2 Software, 96 Hammersmith, Danbury CT 06810. 24 December 1080 © BYTE Publications Inc Quickly reconnoitering your base perimeter, you begin to lay down mines to protect it from invasion. square filled with one of your mines looks just like a stretch of virgin grassland.) As you do this, the steady clickety-click you hear from your opponent's keyboard tells you that he is not exactly idle either—he is probably mining the area around his base, Or perhaps his base is well protected by mountain ranges, and he is now already actively seeking yours? Or maybe he has decided on the decoy ploy, and is building and mining an entirely false base to confuse you? You have no way of knowing! Running out of mines, you frantically return to your base to restock, then rush out again to complete the min- ing operation. Suddenly you hear the sound of a mine ex- ploding. Has your opponent run across your mine field already? Or did he, in his own haste, run afoul of one of his own mines? Thankful you had the foresight to make your mine fields orderly, you investigate: one of them is missing! Your opponent's tank is now badly damaged, but there are still four more where that one came from, and, more important, he now has some idea as to where your base is. Out of mines again, and unwilling to return to base to restock, you are unable to patch the breach—instead, you take off after the intruder, and suddenly—there he is! His tank appears within your tank window! You fire—and miss—he maneuvers, fires—and hits you! Your tank goes into condition yellow—you maneuver, fire—and miss—fire again—a hit! His tank, which was in condition red from having hit the mine, is completely destroyed, but you know that the second of his supply of five tanks has now been made available to him back at his base, wherever that is. Quickly slipping into a nearby forest to survey the area, you suddenly run across what can only be his second tank! You reason as follows: in order for his second tank to have gotten back to this area as fast as it did, his base Circle 17 on inquiry card. —> Vy 4 swesenenls must be nearby. Accordingly, you ignore the fact that his tank begins firing at you, opting instead to try to catch a glimpse of his base in your tank window before your tank is destroyed. You maneuver—are hiti—your tank is now in condi- tion red, and you find it difficult to move prop- erly—nevertheless you forge ahead—there is his base! You move again, and hit a mine—your tank is destroyed! However, remembering the coordinates your tank was at when you saw his base, you make a lightning mental con- version from rectangular to polar coordinates, and, shouting insults across the room to distract your oppo- nent's attention, you swiftly key the polar data into your angle and range registers and fire off an intercontinental ballistic missile from your base. A high, falling whistle is heard, followed by a colossal explosion. A deathly quiet ensues: your condition display glows with the word “SUPREME,” while on your opponent's screen you know the condition to be “DEFUNCT.” You have triumphed in the first game of tonight's seven-game match—as you glance across to see the look of fierce determination on the face of your opponent, you realize that the remaining games may not be won so easily. The judge, looking at both players, slowly raises his hands, and the second game begins. . . . Creating a Game The creation of such a game may not be as far beyond your capabilities as you might think: the above game, in- cluding all features mentioned, and more, has already been implemented for use on a pair of lowly 8 K-byte nm LOPPY DISK FACTORY DIRECT FLOPPY DISK FACTO © Buy factory direct from the manufacturer of floppy disks sold exclusively under other well-known brand names ‘@ Save distribution costs on reversible 5.25” floppy disks, which are 100% certified for 40 track, dual side, double density and ell other standerd applications. © S$0% savings on 5.25" floppy disks with new factory- direct 2.2 megabyte capacity "Diskit". @Factory-direct “Diskit”, includes twelve floppy disks and accessories, plus a head cleaner disk and solution packaged in a bookcase binder for easy access, handling Snd étorage. “Diskit” complete for the introductory price of only $49.50 plus $2.50 freight and hand Normal price $59.50. Order now and save B10. (CA residents add 6 Yo%s sales tax). ‘© Available in hard and soft sector configurations: when ‘ordering indicate number of sectors — 1, 4 or 16. © Send check or maney order to: Factory Direct P.O, Box 60759 ‘Sunnyvale, CA 94088 For VISA or MasterCard call toll-free (800) 824-7888 In Calif. (800) 852-7777 In Alaska & Hawaii (800) 824-7919 Ask for Operator 98 SIO AddO14d LOAWIC AMOLOVS ASIO AddO1s LO SIG AddO1d LOSHIO AHOLOVJ XSIG AddO14 LOSeIO Ad u ACTORY DIRECT FLOPPY DISK FACTORY DIRECT FLOPPY DISK FACTOR 310 ABOLOV = » 26 December 1980 © BYTE Publications Inc Circle 18 on inquiry card. Commodore PET computers, under the name of Flash Attack. (See photos 1a and 1b.) A pair of 16 K-byte PETs, TRS-80s, or Apple IIs should allow the development of even more outrageous games of this general type, perhaps involving quicksand pools, laser weaponry, or aerial reconnaissance, to name a few possibilities. The game could even conceivably be generalized to include more than two players, leading to situations in which teamwork and treachery could become determining factors in a game's outcome, (1a) a cual 7m [ise ad CONDITION (1b) Photo 1: A typical game of Flash Attack fully underway. The photos 1a and 1b show the display screens seen by each of the two players. The two rectangular “windows” seen on each screen represent a limited view of each player's base and the view from his active tank. By presenting only incomplete infor- mation to each player, the skill necessary (along with the cor- responding sense of accomplishment) is increased. Circle 19 on inquiry card. ——> | — ODP 100 is quiet ODP 100 is quietly beautiful QDP 100 quietly works and works and works , beautifully $4695 © 2-80 4 Mhz CPU ® Two 8" Double Sided Double Density Floppies © Four Ports - 2 Serial - 2 Parallel © 64 K Memory ® Disk Controller - Double Sided Double Density - up to 4 M.B. ® Monitor in Prom * CP/M 2.2 DOS ® S-100 (i-€€€) Motherboard ® Aasic Language Included © Real Time Clock Quasar Data Products 10330 Brecksville Rd.. Brecksville, Ohio 44141 216 - 526-0838 216 - 526 - 0839 ee The game hinges on the players’ judicious use of incomplete informa- tion. ee The basic factors that go into making a game like this interesting are threefold: = More than one human player is involved in the game. Rather than having the user compete against the machine, the machine is utilized to permit two or more people to compete with each other in ways that would be impossible without the aid of the machine. Success in the game hinges on the players’ judicious use of incomplete information. Although the game may, in fact, be entirely deterministic in the sense that each legal move a player proposes gets put into effect without the intervention of any randomizing influence, the fact that each player has only a limited notion as to what his opponents are up to lends a definite element of suspense and calculated risk- taking to the game. The game is played in real time: one’s options are constrained not so much by the rules of the game as by one’s own fleetness of hand and mind (or lack thereof). » Many conventional board games, and virtually all con- ventional card games, embody factors 1 and 2, Many video pinball parlor games, such as Atari's Pong and Tank, embody factors 1 and 3, while most of the rest of the available microcomputer game software embodies either none of these factors (computer chess, backgam- mon, etc), factor 2 alone (Star Trek, Adventure, etc), or, in exceptional cases, factors 2 and 3 together (real-time Star Trek, etc). It is interesting to note that, of all the major league sports, the one that embodies all three of these factors most fully is football—this may be the reason why the sport is so overwhelmingly popular. Bringing all three of these factors together in a single computer game virtually requires that more than a single console be used. Since, to most of us, a requirement for multiple consoles is equivalent to a requirement for multiple machines, the issue that will be addressed here is; what is needed in the way of hardware and software to support the implementation of multimachine games? Two-Machine Games In the case of two-machine games, the answer turns out to be surprisingly simple and inexpensive. Most microcomputers come already supplied with a general- purpose, 8-bit, parallel 1/O (input/output) port poking out the back someplace. For those that do not, an add-on port of this type can generally be purchased at nominal expense. As in the PET, the port should ideally have the property that, even though configured for output, it will still return a correct reading of the states of the pins in- volved when a “read” operation is performed on it, Also, as with the PET, the port should represent the high state upon output by means of a passive pull-up resistor. Ports not satisfying these conditions may still be Building Blocks for Microcomputer Systems, Dedicated Controllers and Test Equipment. §-100 ROM, RAM & I/0 BOARD ECT's R*V/O is an S-100 Bus I/O Board with 3 Serial VO Ports (UART's), 1 Parallel /O Port, 4 Status Ports, 2K of ROM with the 8080 Apple Monitor Program and 2K of Static RAM. $295.00 $-100 RACK MOUNT CARD CAGE ECT's RM-10 is a rack mount 10 slot Card Cage with Power Supply, consisting of an ECT-100 rack mount Card Cage (19"W x 12.25"H x 8"D), the MB-10 Mother Board (with ground plane and termination) all 10 connectors and guides and the PS-15A Power Supply (15A @ 8V, 1.5A @ + 16V). $295.00 Specializing in Quality Microcomputer Hardware Industrial ¢ Educational * Small Business » Personal E if Card Cages, Power Supplies, Mainframes, CPU's, Memory, 1/0, OEM Variations ELECTRONIC CONTROL TECHNOLOGY (201) cse-sos0 763 Ramsey Ave., Hillside, NJ 07205 28° December 1980 © BYTE Publications Inc Circle 20 on inquiry card. THE UNBEATABLE S-100 MEMORY That's the MEASUREMENT systems & con- trols DMB Series of S-100 bus memory modules, fully compatible with ALPHA MICRO, CROMEMCO, DYNABYTE, NORTH STAR, MP/M, and most other S-100 systems. Definitely a winner, the DMB Series is avail- able with Bank Select (DMB6400) or without (DM6400} and utilizes industrial quality con- struction, provides outstanding reliability, and ts backed by dedicated customer service and a one year guarantee. The DMB6400 uses I/O port addressing for the bank select feature. A switch provides the abillty to select any one of the 256 I/O ports for addressing the memory banks. The mem- ory Is configured as four totally independent 16K software selectable banks, with each bank addressable on any 16K boundary. stems (en ADivision of MEASUREMENT systems & controls incorporated 3 ¥ Outstanding features such as those listed below make the DMB series the UNBEATABLE S-100 Memory: e Four independent 16K software select- able banks. © Each bank is independently addressable on any 16K boundary. ¢ Switch selectable bank sizes — from 16K to 64K in 16K increments. ¢ Eight banks (512K) per I/O port for each of the 256 ports. e 2-80 4MHz operation with no walt states using transparent refresh. On-board diagnostic LED's. Low power — 8 watts maximum. Reliable, tested and burned-in memory. IEEE S-100 compatible timing. One year guarantee. Attractive Dealer & OEM Prices. See your nearest computer dealer, or contact us for the complete story on the UNBEAT- ABLE S-100 Memory. 887 North Main St. / Orange, Calif. 92668 / (714) 633-4460 TWX/TELEX: 678 401 TAB IRIN a ay Right now, in selected electronics supply stores across the country, Fluke is introducing a new line of low-cost DMM's: the Fluke Series D. With their distinctive dark cases and full range of accessories, these five DMM'‘s are designed to meet the test and measurement needs of the uncompromising service technician, home hobbyist, student or working engineer. Fluke perfected the handheld DMM and set tough standards for accuracy and reliability that have made analog meters obsolete, and oe digitals seem clumsy by comparisot You've obebly heard about their superior electrical performance, mechanical / / Tuggedness and environmental endurance. And now you can see for yourself at your favorite electronics dealer why Fluke 1DMM'°ss have become the professional's choice the world over. Series D Handheld Models. D 800: Fluke's lowest-priced DMM, easy to operate, with six functions, 24 ranges and 0.5% dc voltage accuracy. Guaranteed a full year by Fluke. A sure-fire solution to basic measurement needs. $125." D 802: Basic de accuracy of 0.1% and conductance for high resistance measure- ments to 10,000 M2 make this multimeter a solid price/performance value. $179.” If your dealer doesn’t carry Series D Multimeters yet, call this number. We'll be happy to tell you who does. 1-800-426-9182 D 804: A powerful, versatile handheld D 811: Same performance features as DMM with nine functions, 26 ranges, 0.1% the D 810 with the added convenience of basic de accuracy and more. Direct battery power. Rechargeable “C” size Ni- temperature readings in °C with K-type Cad batteries deliver up to 40 hours thermocouples; peak hold on voltage and continuous operation. $299," current functions; even an audible indicator for instant continuity and logic level Series D Accessories. detection. Available January 1981. $229.* ms A wide range of crneones to extend measurement capabilities of your Series D Bench/Portables. Series D Multimeter is available, including D 810: By means of a Fluke-built hybrid temperature and current probes, carrying converter, this multi-purpose DMM delivers _cases, deluxe test leads thermocouples. True RMS pain ou of ac Me act and a badetp Series D (ese af fad to current with speed precision. economical to own, e features conductance, 0.1% basic de accuracy, made selecting the right DMM much simpler, NOw we've designed an extra 10A range and diode test. $259.* | This is your opportunity to own a Fluke. One for you. suggested US.list price, FLUKE For technica circle no. Circle 21 on inquiry card. 1922@ REM*** INPUT: S# = BYTE TO BE 18230 REM SENT 16248 REM*e* OUTPUTS: NONE 19258 REM 19266 HN = INTCASC(S$9716) 10278 LN = ASCCS$)-HN*16 1028@ POKE 59471,LN+128+32 19298 IF PEEKC59471> AND 128 THEN 198299 18308 POKE 59471,HN+128+64 18316 IF PEEK(C59471> AND 128 THEN 18338 16326 GOTO 16316 1833@ POKE 59471,255 18348 RETURN 19406 REMs* 16418 REM ROUTINE TO RECEIVE BYTE 19426 REM INPUTS: NONE 19438 REMekk OUTPUT: RS = BYTE RECEIVED 18448 REM Listing 1: Listing of the program used to test the cable described in figure 1. 106 REM*** PROGRAM TO TEST INTER~ 116 REM MACHINE COMMUNICATIONS 128 REMxax 288 GOSUB 19888 e21@ IF PEEK¢S9471) AND 16 THEN 268 226 GET S$ 236 IF S$ = "" THEN S$ = CHRSCO) 248 GOSUB 19298 258 IF S$ = "e" THEN 999 266 GOSUB 19400 27@ PRINT R$; 280 IF R$ <> "#@" THEN 229 999 END 19880 REM#K 16618 REPaer* ROUTINE TO INITIALIZE PORT 18926 REM&eek INPUTS: NONE 18926 REM#e* GUTPUTS: NONE 19840 RENkx* 18658 POKE 59471,255 19068 POKE 59459,255 16676 RETURN 19280 REM#x 16216 REMee* ROUTINE TO SEND BYTE used as long as there is provision made within them for individually programming each bit position to be either input or output (examples of the use of such ports will not be given here). What is needed, then, is an arrangement that will allow a byte at a time to be transferred from either machine to the other. Figure 1 gives the wiring diagram for the cable needed; as you can see, each bit position on each machine is simply directly connected to the corresponding bit position on the opposite machine. This is true for all bits except for the 2‘ bit, labeled ASYM, which is grounded on one machine and left floating high on the other. The whole package, including connectors, should cost less than $5, Listing 1 contains a program designed to test the cable. It is designed for use on a pair of PETs, but, with minor modifications, it should be capable of supporting any pair of machines with ports satisfying the conditions discussed above. With the cable in place, and with both machines running this program, what should happen is that any keys hit on either machine should be displayed ‘on the screen of the other. Type a shift-Q (not the STOP key) to exit the program and return to BASIC. The three utility routines of interest here start at lines 10000, 10200, and 10400, respectively. The routine at line 10000 simply initializes the port: location 59471 is the PET’s User Port 1/O data register, while 59459 is the register used to configure the data pins for input and out- put. The POKE in line 10060 configures all eight pins as output. The SEND routine at line 10200 may be called whenever it is desired to send a byte to the opposite 32 December 1990 © BYTE Publications Inc 10458 IF PEEKCS9471) AND 64 THEN 18458 16466 LN = PEEKCS59471> AND 15 19470 POKE 59471,127 18489 IF PEEK(59471> AND 32 THEN 18480 10499 HH = PEEK(59471) AND 15 19588 POKE 59471,255 10519 R$ = CHRSCHN*16+LND 16528 RETURN machine. However, the opposite machine must call its own RECEIVE routine, at line 10400, in order for the transfer to take place. There is a potential pitfall here: if, when writing your own code to use these routines, you create a situation in which both machines are trying to send a byte to the other at the same time, or if both machines try to receive a byte from the other at the same time, both will “hang.” The programs running on the two machines must be set up in such a way that whenever one of them decides to send a byte, the other realizes this and sets up to receive it. Given this fact, the purpose of the ASYM bit in figure 1 becomes evident: it guarantees that start-up problems will not arise when running identical copies of a single program in both machines. Consider yourself in the posi- tion of the program in listing 1 as you begin running; eventually you would reach the point where you would like to start up a dialogue with the other machine. Question: should you send a byte to the other machine first, or receive one? You and the other machine had bet- ter come to complementary conclusions as to which to do first. Solution: you use the setting of the ASYM bit to decide. This is exactly what happens in line 210 in the listing. If, upon reading the port contents, you find that the 2¢ bit is high, you receive first; otherwise you send first. From that point on, in this example, you simply alternate sending and receiving, and ev: is fine. Let's take a closer look at what is actually involved in transferring a byte using this scheme. The nine lines shown in figure 1 can be broken down into four groups: ‘GND. This is a signal ground, which must be present in Circle 22 on Inquiry card. ZORK is more than an adventure. | Zork™ is a computer fantasy of ultimate challenge. Un- earthly creatures guard treasures beyond your imagina- tion. Mazes confound your quest. So quicken your wits * and pick your path carefully through the Great Under- , » ground Empire. The least likely object may be the only thing that can save = your life. Yet, you can succeed. Discover the 20 J treasures of Zork, return them to the Trophy Case and leave alive. But bring all the cunning and courage you can muster. Because in Zork, they take no prisoners . .. Zork, The Great Underground Em- pire, was created by Infocom, Inc., and is available for 32K Apple” II and Il Plus and 32K TRS-80" Model | Level Il disk systems. Also new from Personal Software ADE. is MONTY “ Plays Monopoly,” which (aaC2eics 4 lets an Apple or TRS-80 play Amer- Gh ce ica’s favorite board game with the family. Arcade Classics is a new TRS-80 ry action game featuring Cosmic Raiders, Pinball, Ricochet and J Blockade. A great way to e have fun without feeding fe! = - quarters into the machines. , . Zork, MONTY Plays Mon- =r? —sopoly and Arcade Classics— more fun and games with your computer, now join- ing our other Strategy Games: Microchess, Gammon Gambler, Checker King, Bridge Partner and Time Trek. See these great strat- egy games at your Per- sonal Software com- puter retailer, For the dealer nearest you, call Personal Software Inc. at 408/745-7841, or write 1330 Bordeaux Drive, Sunnyvale, CA 94086. When you put your computer to work, use Personal Software™ Pro- ductivity Products: VisiCalc" DESKTOP/PLAN™ and CCA Data Management System. MACHINE A @-BIT 1/0 FORT 2O DATA 3 2 2 MACHINE 8 8-BIT 1/0 PORT 2O DATA 2 2 20 OATAL Oz 2O DATAO > 2° GROUND th Figure 1: The cable arrangement needed for connecting two PETs in game-playing configuration. Each machine runs the same pro- gram, and sxohanyes relevant information, one byte at a time, with the opponent's computer. The bit labeled 2* determines the initial ac. state of each mi ine and, thus, whether it first transmits or receives. a DATA 0-3 \ hk / Figure 2: Timing diagram for information transfer using the cable scheme of figure 1. The transmitting computer puts information on the DATA lines, low-order nybble first, and brings the line low. The recetving computer brings the DRCV line low when the in- formation has been accepted. The process is repeated for the high-order nybble, but HNR is used to indicate the presence of new data. When DRCV is brought high, the transmitter and receiver functions reverse. order for the two machines to have a common reference voltage. @DATA 0 thru 3. These lines, which are controlled by the sender, carry the actual data being transferred, a nyb- ble at a time (a nybble is half of a byte, or 4 bits). @ ASYM. This has already been discussed. @DRCV, INR, and (data received, low-order nybble ready, and high-order nybble ready). These are the so-called “handshake” lines. CNR , which is a signal from the sender to the receiver, is brought low by the sender to indicate to the receiver that the low-order nyb- ble of the byte being sent is now ready to be read off of the DATA lines. ANR also a signal from the sender to the receiver, is brought low by the sender to indicate to the receiver that the high-order nybble of the byte being sent is now ready to be read off the DATA lines. DRCY, which is a signal from the receiver to the sender, is brought low by the receiver once he has read the low- order nybble off of the DA