A 6502 Version Of The Winter Consumer Electronics Show
The 6502 Resource Magazine
Clearing Apple It's Low- Resolution
PET • Apple • Atari • OSI • KIM • SYM • AIM Graphics Screen
COMPUTE!
The Journal For Progressive Computing
$2.50
March, 1981
Issue 10 Vol. a No. 3
Designing Your Own Atari Character Set
Machine Language Taking The Plunge
Keyprint (For The Pet) Revisited
Six-Gun
Shootout Game For The OSI C1P
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Mountain Computer
can now
EXPAND
Your Apple II Peripheral Capacity
EXPANSION CHASSIS
Quality You Expect
Eight more slots for your Apple! Now you can bank-select eight more peripheral slots with immediate or deferred software commands— like having upto 15 peripheral cards "on line"— or use the Select/Deselect switch mounted on the front panel. Expansion Chassis' heavy-duty power supply is primarily for peripherals, without the heavy demand of motherboard support chips required in your Apple. This means much more power is available for peri- pherals than in your Apple itself! If you've run out of room in your Apple — Expansion Chassis isyouranswer. Drop by your Apple dealer for a demonstration, or contact Mountain Computer for the location of the dealer nearest you.
Performance You Demand
• Eight mirror image I/O slots of the Apple
• Fully buffered, bi-directional data lines
• Apple II compatible interface card
• Dual selection capability; hardware or software
• Immediate or deferred selection in software mode
• From BASIC, a single POKE command turns the chassis ON or OFF
• Compatible withal software
• Dedicated powers jpply with approved power transformer
0^ Mountaiin Computer
(Si^_: I NCOBPORATKD*
300 Harvey West Blvd., Santa Cruz, CA 95060 (408) 429-8600 TWX 910 598-4504
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March. 1981. Issue lO.
COMPUTE!
IF YOU'RE WAITING FOR THE
PRICE OF WORD PROCESSORS
TO FALL WITHIN REASON,
l^gggi
Everyone expected it would happen sooner or later. . .with WordPro PLUS" it already has! Now all the marvelous benefits of expensive and advanced word processing systems are available on Commodore computers, America's largest selling computer line. WordPro PLUS, when combined with the new 80 column CBM 8032, creates a word pro- cessing system comparable to virtually any other top quality word processor available — but at savings of thousands of dollars!
New, low cost computer technology is now available at a fraction of what you would expect to pay. This technology allowed Commodore to introduce the new and revolutionary CBM 8032 Computer.
WordPro PLUS turns this new CBM 8032 Computer into a sophisticated, lime saving word processing tool. With WordPro PLUS, documents are dis- played on the computer's screen. Edit- ing and last minute revisions are simple and easy. No more lengthy re-typtng sessions. Letters and documents are easily re-called from memory storage for editing or printing with final drafts printed perfectly at over five hundred words per minute!
Our nationwide team of professional dealers will show you how your office will benefit by using WordPro PLUS. At a price far less than you realize.
invest in your office's future. . . Invest in WordPro PLUS. . , Call us today tor the name of Ifie WordPro PLUS dealer nearest you.
Professional Software Inc.
166 Crescent Road Needham, MA 02194 (617)444-5224 TELEX; 95 1579
Memory —you never seem to have quite enough of it.
But if you're one of the thousands of Apple owners using the SoftCard, there's an economical new way to expand your memory dramatically.
16K0NAPIUG-INCARD.
Microsoft's new RAMCard simply ^ plugs into your Apple 11,® and adds 16k bytes of dependable, buffered read/write storage.
Together with the SoftCard, the RAMCard gives you a 56k CP/M® system that's big enough to take on all kinds of chores that would never fit before (until now, g the only way to get this much memory was to have an Apple f Language Card installed). 'j-
GREAT SOFTWARE: YOURS,OURS,OR THEIRS. |
With the RAMCard and SoftCard, you can tackle large- scale business and scientific computing with our COBOL and « FORTRAN languages. Or greatly increase the capability of CP/M |
II
applications like the Peachtree Software account- ing systems. VisiCalc™ and other Apple software packages can take advantage of RAMCard too.
And RAMCard gives you the extra capacity to develop advanced programs of your own, using the SoftCard and CP/M. Even with the RAMCard in place, you can still access your ROM BASIC and monitor routines,
^ JOIN THE SOFTCARD
FAMILY.
The RAMCard Is just the latest addition to the SoftCard I family —a comprehensive sys- tem of hardware and software I that can make your Apple more versatile and powerful than you ever imagined.
Your Microsoft dealer has all the exciting details. Visit him soon, and discover a great idea that keeps getting better.
Microsoft Consumer Products, 400 108th Ave. N.E., Suite 200, Bellevue, WA 98004. ■^ (206)454-1315.
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Morch, 1931. Issue 10,
COMPUTE!
Table of Contents
March, 1981, Vol. 3. No. 3
The Editor's Notes Robert Lock, 4
A Beginner's Guide to Compute! 9
A 6502 Version of ttie Winter Consumer
Eiectronics Show: January '81 David Tlnornburg, lO
The Beginner's Page Robert Locl<, 12
Computers end Society David Thornburg, 14
Taking the Plunge-Machine Language
Programming for Beginners Richard Mansfield, 20
Computer Communications Experiments Marvin L. DeJong, 28
Basics of Light Pen Operation Robert A. Peck, 36
Getting the Most from your Pet Cassette Deck , . . Louis F, Sor^der, 42 The Mysterious and Unpredictable
RND-Part 3 Bob Albrecht and George Fired rake, 48
A CAI Program Called Linear Equation Peter Ookes, 54
Hex Conversion Using the 6502's Decimai Mode Jack Clarke, 60
The Apple Gazette 62
Clearing the Apple II Low-Resolution
Graphics Screen Sherm Ostrowsky, 62
Fun with Apple and PASCAL Gene A Mouney, 68
Flipping your Disk Ivl, G. Sieg, 71
The Atari Gazette 72
Designing Your Own Atari Character Sets Craig Ratchet!, 72
Atari Basic: A Line Renumbering Utility D, IVI, Gropper, 78
Atari Memory Dump and Dlsassembier Robert W, Bal<er, 8C
Formatted Output for Atari Basic Joseph J. Wrobel, 84
Random Color Switching while idle R, A Howeli, 85
The OSI Gazette 87
A Small Operating System: OS65D the Kernel Tom R. Berger, 87
A Six-Gun Shootout Game for the OSI CIP ... Charles L, Stanford, 88
The PIT Gazette 92
Keyprint Revisited Eric Brandon, 92
Learning About Garbage Collection Jim Butterf ieid, 96
PET Machine Language Graphics David IVIalmberg, 102
Disk File Recovery Program David L. Cone, 112
PET Exec Hello Gordon Campbell, 124
A Flexible input Subroutine Glenn M. Kieiman, 130
Universal Tope Append for PET/CBM Roy Busdiecker, 132
The SBC Gazette 138
Nuts and Volts Gene Zumchck, 138
Experimenting with the 6551 ACIA Marvin L DaJong, 142
A Vocal Hex Dump for the KIM-1 WiliiomC. Clements, Jr., 146
Expanding KIM Style 6502 Single Board Computers
-Part 3 of 3 Hal Chomberlin, 150
Cassette I/O with AIM-65 BASIC Michael Rathbun, 152
New Products 154
CAPUTEi Robert Lock and Authors, 164
Writing for COMPUTE! 166
Advertisers Index 168
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AUTHORS
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COMPUTE! The Journal for Progressive Computing (USPS: 537250) is published 12 times each year by Small System Services, Inc., P.O. Box 5406, Greensboro, NC 27403 USA. Phone: (919) 275-9809. Editorial Ofiices are located at 200 East Bessemer Ave., Greensboro, NC 27401.
Domestic Subscriptions: 12 issues, J20.00. Send subscription orders or change of address (P.O. Form 3579) to Circulation Dept., COMPUTE! Magazine, P.O. Box 5406, Greensboro, NC 27403, Controlled circulation postage paid at Greensboro, NC 27403. Application to mail ai controlled circulation rates pending at Hickory, NC 28601. Entire contents copyright © 1981 by Small System Services, Inc. All rights reserved. ISSN 0194-357X.
I ^MPjngiri
COMPUTE!
March, 1981. Issue 10.
Robert Lock, Editor/Publisher
Software Copying Revisited, Or Who's Paying The Bills?
We recently received an extensive letter from a Canadian subscriber commenting on the January editorial regarding software piracy. I'd like to respond to one specific point of the letter now, and request other readers to respond at length as well. Let's get the dialogue rolling, and we'll continue it from here. I really think it's a critical turning point in the industry's future development. I don't presume to suggest we can solve it here, but I'd like COMPUTE! readers to help spark and maintain the dialogue. Here's the prompting remark from the reader;
/ agree to a great deal with your comment on copyright of magazines and books and software. I disliked your generalizations about schools. Schools are rather like big businesses. If a business has a number of machines and purchases say a "General Package", is it really break- ing copyright to make enough copies to be used on all its machines? I don't think so. I reckon schools are in a similar situation. . . First of all, your comment presumes that big business has the right to copy (reproduce) proprietary software. They don't have the right to do so any more than Commodore (for example) would have the right to buy one copy of a program and give it away with all of their computers. Frequently, "big business" is able to buy a piece of software with limited license rights, they pay additional fees. This is not the case with the software we're talking about for our marketplace. I'd like to propose an analogy... suggested by an individual involved in software sales. He commented on a "textbook defense" of software theft, and I'll expand on it here:
Let's assume that you've taken your notes and teaching experiments from the last few years, and spent a recent summer developing them into a textbook, complete with student workbook full of exercises.
You find a publisher, obtain a contract wherein you receive a royalty on sales, go through numerous editings, and finally see your first copy in the mail.
Your book is selling for $19.95, and you're looking forward to some return from your royalties.
Time Passes
Sales are going along okay, but not up to your ex- pectations. I mean it is an excellent book. You attend a regional educational conference, and run into Dr. So and So from a neighboring school district. He
says, "We really enjoyed your new text, and it's super! We're using it in all of our classes next year."
Great (you think). Hundreds of sales. "Oh, by the way," he continues. "We thought $19.95 was pretty expensive, so we only bought one copy. We're running off class copies in our own print shop. . .See you later."
There goes your work, and your royalty. I assume you're concerned, if not angry. Is this any different in principle, from the defense of schools and software copying. Now we all know that realistically, the book would be rather expensive to duplicate. And I presume no one would doubt the illegality of the act. The essence of the argument would seem to become one of ease and expense of the copying. Soft- ware comes on an inexpensive, easily transportable media. Therefore, does copying it suddenly become okay? We need to give thought as well to the pro- ducers of the work. With commercial software, there's someone out there, after some amount of hard work, patiently waiting for their royalty.
I would suggest that users should not define a $19,95 software purchase as an unlimited right to copy, just as they wouldn't consider doing the same with a $19.95 textbook.
It would be more appropriate to approach pro- ducers about school licensing agreements, or multiple copies at school discount through their vendors, or whatever. This rational (negotiated) approach, if you will, would solve problems for several parties. . . Schools who currently buy multiple copies of soft- ware would save money, schools (individuals) who currently buy and reproduce would have full vendor support, and so on. The vendor support is an ele- ment we haven't touched on, but is part of the whole problem. I've been told, essentially, "Why should I support the educational market? They just steal my stuff."
A Post-Script
These comments should in no way infer that most- schools aren't absolutely honest in their software pur- chases. We're just using this initial analogy to get the ball rolling. We've heard recently of a major in- dustrial research center on the West Coast that's using approximately 80 copies of a $150.00 plus soft- ware package . . . copies cloned from their original single copy purchase. And how many times have you picked up that "back-up" copy of Cursor magazine to use just this once?
Defining The Right Of Bacic-up
Several other magazines in the industry have recently been running advertisements for a program that copies (duplicates) protected software for a particular
ATARI: PERSONAL
COMPUTER SYSTEMS THAT
GROW WITH YOU
Start with a better computer.
Atari computers have built-in capa- bilities you can't even add onto many other personal computers. Three programming formats (ROM cartridge, disk and cassette), A 57 key upper/lower case ASCII keyboard with 39 keystroke graphics symbols. 128 colors and hues. Four separate sound channels and a built-in speaker. Four controller ports. A built-in RF
©1980. Alan, Inc.
O A Warner Communications Company
Atari reserves Ihe righ! to make charges to products or programs wilhool notice.
modulator and FCC approval for connection to any TV Plus, nationwide Atari Authorized Service Centers. And more.
Add memory. The ATARI
800^" is supplied with 16K of memory. You can expand up to a full 48K of RAM with 8K or 16K Memory Modules"" you install yourself. In less than a minute. The ATARI 400's" 8K of RAM may be expanded to 16K at Authorized Ser- vice Centers. Both may be expanded to 26K of ROM with slip-in ROM cartridge programs.
Add peripherals. The ATARI 410"' audio-digital program recorder Sin- gle or dual density* disk drives. The ATARI Soo individually addresses up to four drives. Add the ATARI 850™ RS232 Interface Module, Add high speed 40 or 8o-column printers. Add an acoustic modem for remote data access. Add a light pen.* And there are more Atari peripherals on the way.
■■I 3'
A-
ATARI
Add programs. Choose among doz- ens of programs in Atari's rapidly expanding software library. Programs categories include:
• Personal Finance & Record Keeping
• Personal Interest & Development
• Professional Applications
• Education
• Information & Communfcation
• Entertainment
• Programming Languages
• Small Business Accounting
Add it up. With Atari, you start with more. And you can build to more. Because Atari offers you per- sonal computer systems that grow with you. Ask your Atari retailer to give you a full demonstration of Atari computers, peripherals and programs. Complete systems. Because when other people were thinking hardvrare and software. Atari was thinking systems.
"'Available FaH. 1980
PERSOWAL COMPUTERS
:;65 Bortegjs Avenue, Sunnyvale, CA 94086
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COMPUTEI
March, 1981. Issue 10,
Staff
Robert C. Lock, Publisher/ Editor Kathleen Martinek, Publication
Assistant Georgia Papadopouiis, Art Direction/
Production Assistance Joretto Klepfer, Manager, Dealer/
Distributor Marketing Carol Holmquist Lock, Circulation
Manager Dai Rees, Shipping Department Charles Brannon, Software Lob
Assistant
Associate Editors
Jim Butterfield, Toronto Canada Harvey Herman, Greensboro, NC
Contributing Editors
Robert Baker, 15 Windsor Drive,
Atco, New Jersey 08004 Gene Beals, 115 E. Stump Road,
Montgomeryville, PA 18936 Len Lindsay, 5501 Groveland
Terrace, Madison, Wl 53716 Craig Patchett, 2 Swan Terrace,
Greenwich, CT 06830
Subscription Information
(12 Issue Year):
COMPUTE! Circulation Dept.
P.O. Box 5406
Greensboro, NC 27403 USA
U.S, $20.00
Canada $25,00 {U,S, funds)
Europe: Surface Subscription, $25,00 ("U.S.
funds) if ordered direct, or avoilobie inlocol
currency from ttie foiiowing distributors:
United Kingdom
Contact L. P. Enterprises,
8-11 Cambridge House
Cambridge Rood
Barking, Essex
Engiond IGl 18NT
Germany,
Switzeriand,
Austria,
Contact ing, W. Hofacker GMBH
8 fvlunclien 75
Postfach 437
West Germany Canadian Retail Deaiers should contact: Micron Distributing 409 Queen Street West Toronto, Ontario M5V 2A5 (416) 361-0609
Authors of manuscripts warrant ttiat all materials submitted to COMPUTEI are original materials with full owner- ship rights resident in said outhors. By submitting articles to COtvlPUTEl, authors acknowledge that such materials, upon acceptance for pubiicotion, become the exclusive property of Smoll System Services. Inc. No portion of this magazine may be reproduced in any form without written permission from the publisher. Entire contents copyright © 1980, Small System Services, Inc. Programs developed and submitted by authors remain their property, with the exception that COMPUTE, reserves the right to reprint the material, as originally published in COMPUTEI, in future publications. Unsoilcited materials not occepted tor publication in COMPUIfci will be returned if author provides a self-addressed, stamped envelope. Program listings should be provided in printed form (new ribbon) as weil as machine readable form. Articles should be furnished as typed copy (upper and lower cose, please) with double spacing, Eoch pane of your article should bear the title of the article, date and name of the author. COMPUTEI assumes no liabilitv for errors In articles or advertisements. Opinions expressed by authors are not necessarily those of COMPUTEI. PET Is a trademark of Commodore Business Machines, inc. Apple is a trademark of Apple Computer Company, ATARI is a trademark of Atari. Inc.
Advertising Sales
If you re in Oklahoma, Texas or the Western States, we're now represented by Jules E. Thompson, Inc. Give thiem a call for space reservations, contract/ insertion information, or questions, You can reachi thiem throughi the following of- fices:
Southern California, Arizona, New Mexico Jules E. Thompson, Inc. 2560 Vic Tejon
Polos Verdes Estates, CA 90274 213 378-8361 Jo Ann Sullivan Northern California,
Pacific Northwest, Rocky Mountoin States, Texas. Oklahoma Jules E. Thompson, Inc. 1290 Howard Avenue, *r303 Burlingame. CA 94010 415 348-8222
Phoebe Thompson
If you're in the East, we're now represented by The Gittelman Com- pany. You con reach them through the following offices; New England, New York State The Gittelman Company Statler Office Building Suite 482
20 Providence Street Boston, MA 02110 617 451-0822 Joan Donahue New York City Metro Area, Mid-Atlantic and Southeastern States: Local numbers: New York 212 567-6717 Atlanta 404 523-1252 The Gittelman Company Summit Office Centre 7266 Summit Avenue Fort Washington, PA 19034 215 646-5700 Doug Johnson
Address all advertising materials to: COMPUTE
200 East Bessemer Avenue Greensboro, NC 27401 USA
Mailing address: COMPUTEI
Post Office Box 5406 Greensboro, NC 27403 USA
Telephone: (919) 275-9809
Apple World
3-D ANIt-'ATED COLOR GRAPHICS Wfitier in machine coae The program mide f«moui on nationiJ T.V.! by Pa^Jl Liilj5
APPLE WORLO turns ycur A|>pi'p miD a sophisucaied graphics system capable ol Limi\\nQ arrnnated ihi-ee Cimcrisionai coloi images proiecimg mem m Irue perspecll^fe an me screen, rotate Ihgm. move Thpm closer , further away. ari3 mdny Dither gxCtting and imaginatLve mmgs
Draws obiecis wiih 6S 000 pOiriis per side
A powej-iuf screen-oriented te*! edilor is mcluded to , laciliiaie image fomatiori This program w^^ rr^rently leatuied on Tom Snyfler s Hnnve Time SatufOay TV ShoM and n now available for sale
APPLEWORLDSpowerlulea lions so easy to use rfi^I cfiiidreriwill sovcit Voucan i^ow sketch 'yoyfdrearrr tnouse. boat, car, or fantasy i?mD[(e Then view it as it would Deseen from lO.OOOteeLoryoucani ZOOM ir until the screen is tilled with a doorknob You could Iherv go ms^dc and mnve from Foom to room t examining lumiiu'e placement as yatit screen rotates wilhm itie room Images or speciiic parts o( iinages CAfi «asily be saved to disk or pnnler
Does all mjs sound like science fiction?
u won tlfiinhsoatief younave viSiteo Apple World.
INTRODUCTORY PRICE S59.95 , For 46K Apple II or Plus with Disk
^Snpergraphics
M M ¥
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4 3D GAt/t DEVELOPMENT SYSTEM IM COLOR Df Paul Lulus
Waicn colorful Diiltefllys Ciras. f^'i acfoss your Apple uf Aiari screen wntn true 3 Dnrnenssonal perspective Have rocKelSliipSlly Out a( ysj m tf.is mcrediDle Migti speeo graphics package 3-D SUPERGRAPHICS" is a 6502 machii^* language pfogram tnal will inlertace 10 yOur Basic or machine language programs or games usmg simple "DOS-lihe' commands,
F««turei include:
• Simple image entry mrougn eo<tQr
• OPteds up to 25fi points p^r Side
• Uses all fii-res colors
• Allows mixed colored tejd & graphics lor promcts and caption?
• Translates on 3 anes Individual axi^s scales ?1 d'lfereni commanas Roiaie object i 4" to 360' inc'emenis at machine &pe«d^
FOR 4BK APPLE U OR PLUS WITH DISK II £39.95 FOR DISK
FOR ATARI 800 WITH 40K MEMORY (DISK OPTIONAL)
$39.95 FOR TAPE
L^ OTHER SOFTWARE
^^^ APPLE COMPUTERS
Super Space Wais S 3 95
L Slater fi Capitals ^95
^^■^ Moving Point
■^^^ Average 1995
^ Stock Options. ... 24 95
frnance -. - i£95
fc Bonds 12 95
^V^ COMMODORE PET
r SiocK Options ..-- 24 95
Finance 12 95
k^ Bonds 12 95
^^mf Stock Analyser 22 95
^^^ Morlgage 14 95
r Space NilrgflerS I'-Besi
Game of 19?9'1 I9 95
_^m^ Kentucky Oefby/
"^W|^ Roulette 9.95
r Alien I Q .Tar^k 9.95
Submarine Attack 9 95
W^ Ballle ol Midway 7 95
^^■^ Laser Tank Batlle 9 95
"TPV Swarm 14 95
r Baseball 9 95
Super Siarirek u 95
k PETMuSicBOJt 29 95
^^■v Music Composition Si'slem
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r Pearl Harbor Adventure ......
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Super Gomoku 9 95
March, 1961. Issue lO.
COMPUTE!
Relational Query System For Management
DATABASES: YouVe Heard The Hype Before... The Truth IS... REQUEST DELIVERS!
DATABASE MAINTENANCE —
• Uses sophisticated screen formatting & Oata entry, like on IBM 3270's!
• Generates its own screens automatically!
• Handles records up to 4K in length, using multiple screen "Pages"!
• Automatic data compression for increased disk capacity
• Uses Superkram (See below) access metfiod for incredibly fast access, LESS THAN .2 SECONDS FOR A RECORD!
• Automatic index creation/maintenance
• Automatic maintenance capabilities
• "Goof-Proof" error fiandling
• Input can come from VISICALC" or
SOURCE-
DATABASE SELECTION—
• Uses screen masks to form query
• Provides extensive search capabilities
• Search arguments can include arithmetic/boolean functions, multi-field comparisons
• Queries can generate input for automatic database maintenance
• Queries can be stored in "Query Library" and executed from menu on demand
• Any number of fields can be queried concurrently
• Query output can be routed to disk. CRT report formatter. VISICALC" or SOURCE'"
ONLY $225
DATABASE REPORTING—
• Automatic tieadlines
• Automatic field editing
• Report fields can be calculated, sub-iolaled & cross-footed in any manner desired.
• Optional counter tjreaks may be set
• Automatic grand totals
• Automatic statistics
REQUIREMENTS
Superkram (see below) and: Commodore Pet 32K (40 or 80 col) and 2040/4040/8050 disk OR Apple II 48K with Applesoft or language system and 2 disk drives or CORVUS.
SUPERKRAM
Now With Multi-Key
Capabilities
For Apple & Pet
by K«n Germann
Since KRAM"" was introduced inl 979 it has fast become known as the quickest and most powerful access method for serious Apple and Pet users. Now, after hundreds of requests we have added MULTI-KEY, MULTI-INDEX, functions, as well as increasing processing speed.
tBM/370 usefs have VSAM (Virtual Siorage Access Meihodl lo provide fasi, flexible iiey«l-acces5 10 irifiirdata Nqm SUPER KRAM (Keyed Ranaom Acces? Method |. tjom UnDtedSoTlwsre of AmerHca. gives Apple ana Pet users the same riembiliTy. sutJBtanTiaNy increasing ihe processing power 0I me Apple and Per
UntiJ SUPER KRAM %hv onry 'lamiom access ' capabiiiry in the Apple and Pel consisied of a crude lorm o' "relative record" processing While Ihis u usable tor very sirnpleapphcaipons. it t3\\$ lar snort oi the needs c( today s btjsmess and analytical applicalJons Using SUPER KRAM records may be processed Cy any one oi mulliple "Key " wafues. which may consist oi any kind ol data: rumbers. letters, special charaaers. etc Even Appless long- awaited DOS 3 3 doesn I have anyihing htie this!!
KflAM'" 2,0 Only $99,95 SUPER KRAM" Only S175
KRAM" 2.0 ReguJar Features
• Wdtien in 6502 machine ccxJe Basic cornpatibic
• Cieate Open a daiasei
• Put Fecord by hey
• Ada A. delete records by key
• Get any recoid by FuU.Pariiial hey
• Acc«sby any key inaiiiitleas 5 sec [ 1 sec with Corvusdiih)
• Suppofis mullipie cjisks
• Read ncKl Of D'evious lecofd
• Dynamic space allocation
■ Dynamic space reclamation
• Dynamic inees compression
• Files rievLM need leoirganif ition
• Compatible with l^r^guage syslerns
ATTENTION-EXISTIMG KRAM USERS,
SenQ Si5 wjth original disk and ROM lo Uniied Software lor jmprovecf version 0
SUPER KRAM'S " Added Features
• MULTiKEY SUPPORT - Avowing simultaneous access to a K^AU iile bf more Than one ^^ey field
» HI-SPEED HEAD — This texture allows mci'eased'I'Ospetaup to 60S faster during processing of SUPER KRAM read next. lead prevKOus put ana delete requests
• IMPROVED INDE^f ARCHITECTURE - Allowing taster inden searchers and more Bitjcient disk Space utilizaiiOn
■ INTEGHATED BASIC COMMANDS - Allowing SUPER KRAM- commands to be coded in-line witn Basic, providing easier usage ol KRAM than ever before
• USER-SPECIFIABLE BUFFER POOL - Allawirg (he user to specpiy how many KRAM files a re allowed open at one lime: will support any rtunsbe/ ol KRAM tiles
• LOGICAL RECORDS {KEYS WAV BE NON UNIQUE) - Records added lo the KRAM files ore tmrrrediately accessible by Any of the dofiinBd keys lor the liiic [Automatic Upgrade)
• KRAM 2 0 liies are totally compaiible with SUPER KRAM
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The model 80 features an industrial grade metal cabinet with built-in disk mounting capability and space for an 11 " x 14" PC board for custom designed electronics. Front mounted controls include power, contrast, horizontal hold, vertical hold, and brightness.
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Amdek Cora the new name for Leedex . . . Expanding for the future, growing with success.
March. 1981 Issue 10.
COMPUTi!
machine. One of the magazines (Micro) checked with us to see our feelings on such advertising. We in- dicated that we wouldn't run such ads, given that the software in question could be used to produce duplicate copies of "protected" and proprietary soft- ware. Wc understand that Micro has since decided to do the same.
We applaud this move toward protecting the rights of the software industry, and encourage addi- tional comment.
The Rights Of The Buyer
This isn't intended to be an inclusive comment on the rights of software buyers, but an attempt to open discussion. I already know of one COMPUTE! Associate Editor who has definite feelings on the sub- ject. We'll try to get him involved in the discussion on these pages.
The buyer of a copy-protected diskette has potential problems, and deserves to be protected as well. Vendors of software would remove the legitimate need for copying software if they would adopt a customer oriented, fully responsive plan for allowing licensed owners of software to quickly, con- veniently and most of all, economically, obtain a back-up in the case of iailure of a diskette.
The principal of repetitive back-ups is rightly embedded in the history of data processing tech- nique, and can't be ignored in an industry rush to protect proprietary software from duplication. Per- sonal Software appears to be trying to deal with this with Visicalc, and I'm sure other vendors are as well. The vendor has the right to protect proprietary software. The vendor also has the obligation to pro- tect the customer's interest. The extent of this protec- tion of the mutual interests of both will ultimately help define the e.xistence of the protection violation market, and the strength of the software market as a whole. We'll eagerly await your comments.
The Boston Commodore Show; VIC Meets The Consumer
Judging from the interest in VIC at Commodore's Boston Show (February 6, 7), the $299.95 color com- puter entry from Commodore will be well received. One of the biggest unresolved problems of the moment is: "When will production be up and run- ning?" They're currently saying March-April, and I think they'll make it. BASIC, by the way, is the well-known upgrade ROM set, and color animation capabilities are rather nice. We hope that Com- modore will see their way to a nice introductory package price. Watch our April issue for a full review of VIC, and mid- April for the availability of our brand new quarterly magazine, exclusively for the VIC. It's called Home and Educational COM- PUTING!, and is announced elsewhere in this issue.
Atari Update
They're still selling as fast as they can make them. What else can we say? @
A Beginners
Guide To COiVIPUTE!
If you're just getting started with your computer or with COMPUTE!, here are several notes to help you use COMPUTE!:
Presentation
In every issue we try to present a balanced group of articles ranging from material for beginners to material for old hands. Frequently, a beginner can get a great deal out of an ad- vanced article, even though much of it may be over his or her head.
Program listings are presented as legibly as possible. Pet programs are generally reproduced and reformatted here where we've developed software to "translate" the special Pet graphics characters into characters printable by our equipment. These are explained below:
Program Listings for COMPUTE
Cursor control characters will appear in source listings as shown below:
Jl=HOME , fi=CLEAR SCREEN
^=DOWN CURSOR , T=UP CURSOR
>=RIGHT CURSOR, <=LEFT CURSOR
jl^REVERSE , f = REVERSE OFF
Graphics (i.e. shifted) characters will appear as the unshifted alphanumeric character with an underline. This docs not apply to the cursor control characters. The Spinwriter thimble doesn't have a backarrow symbol, so a "-"" is used instead.
The "-n" is used to indicate the beginning of a continuation line. It is also used to indicate the end of a line which ends with a space. This prevents any spaces from being hidden.
If, for example, you're an Apple owner using a Pet program that's reproduced in this fashion, you'll need to be familiar with these special characters so you can program around them. As more computers implement versions of Microsoft BASIC, the programs should become more and more transportable. @
Reader's Feedback will return next issue in a revised and expanded format. Keep those letters and editor's feedback cards coming. By the way, see our New Products section, new this issue. RCL
X)
COMPUTEI
Morch, 1981. Issue lO.
A 6502 Version Of The
Winter Consumer Electronics Show: January, 1981
David D. Thornburg
Innovision
P.O, Box 1317
Los Altos, CA 94022
At a time when most normal folks are taking down the holiday decorations, and preparing for the new year, those of us who haunt the trade shows were anxiously preparing for our January fix — the Winter CES (Consumer Electronics Show) held in Las Vegas. Unlike specialized trade shows, like Comdex, the CES has exhibits covering almost all consumer products that arc likely to contain silicon. Because of the continuing recession, only 55,000 people attended this show which was held in the Las Vegas Convention Center and in two nearby hotels. Rather than describe some of the more novel pro- ducts, such as the talking microwave oven (with, would you believe it, a Japanese-English accent), or the solar rechargeable flashlight (look, I couldn't make this stuff up if I tried, so believe mc!), I de- cided to mention some of the products of greater relevance to COMPUTE! readers: the 6502-based microcomputers which were displayed.
As far as hardware is concerned, the big hit of the show was the Commodore VIC-20 (your fearless scribe is preparing a review of this machine to appear in a forthcoming issue of COMPUTE!). At a suggested retail price of $299, it is apparent to me that Com- modore has the technical ability to give the Radio Shack Color Computer a solid run for its money. In fact, I expect VIC sales to place Commodore firmly in the number two spot for total machine placements, and perhaps to even edge up on our Texas friends. The styling is beautiful and the price is right, but even more importantly, Commodore is going all out to support the cottage industry that has kept the PET well supplied with software. Watch for the FCC ap- proval, followed by the VIC showing up in your cor- ner computer store sometime in March or April,
Software had its day at CES also. Atari showed both their new PILOT cartridge (see this month's Computers and Society column), and also showed their word processor package. Both pieces of soft- ware are very well done, and should do much to help Atari on its accelerating growth curve. While I didn't see any new Atari hardware on the floor, there were rumors of some nice new things hidden away in their hospitality suite. It is apparent that Atari is in this game for the long haul.
Those of you who are waiting for the keyboard portion of the Mattel Intellivision (complete with a 6502-based computer with 16 K of RAM and a Microsoft BASIC) will have to wait a little longer. Once again they say that deliveries will begin in March — only the year has changed.
The absence of Apple and OSI from this show was noted. Apple has apparently decided to focus its efforts in the small business market, and leave the home computer market to fend for itself for awhile. I saw lots of Apple folks at the show, however, so they can't have totally lost interest in the consumer
For those of us who hove invested in 6502-based systems,
it is heartening to see that this
processor continues to be among
the most popuiar.
market, OSI, on the other hand, has had nice ex- hibits at this show for quite some time, and I have to assume (without checking it out) that their absence was due more to their recent acquisition than to any plans they have to depart from the low-end market.
The 6502-based hand held computer from Matsushita (which will be marketed both through Panasonic and Quasar) was shown running a com- munications interface hooked up to the Source. It ap- pears that the software for this computer is almost finished, and that we can expect to see it hit the market in a few months. Considering that this com- puter, with modem and coupler, will have a retail price in the $1,000 range, I find its small keyboard and one-line liquid crystal display to be annoying. On the other hand, if you want the ultimate in por- tability, this might be just the computer for you.
It was interesting to note that all the other com- puters at the CES (excepting the TI 99/4) used either the 8080 or Z-80 microprocessor. There were no new 16-bit computers introduced. For those of us who have invested in 6502-based systems, it is heartening to see that this processor continues to be among the most popular. It is clear that our investment will re- tain its value for quite some time.
March, 1981 Issue lO.
COMPUTE!
IN 1981...
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• On-screL-n preparation using facsimile of IRS forms
• Year-long record-keeping and building of itemized files
• Numerous tax alternatives easily analyzed
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• Fully compatible with all printers
• Use u'ith or without line printer
• Use with or without two disk drives
• Includes full documentation, sample returns, and two disks (program disk and storage disk)
Available at your dealer for $99 (suggested retail)
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12
COMPUTE!
March, 1981 issue 10.
The Beginner's Page
Robert Lock, Editor/Publisher
COMPUTE! is a specialized resource magazine that provides editorial coverage of a family of micro- computers that share a common "central processing" chip — the 6502. With the proliferation of small computers, we find that you can obtain more useful and relevant information in a magazine that doesn't (for example) cover the TRS-80 computer line. It, by the way, uses a different microprocessor chip: the Z-80. A whole different family of chips, and a dif- ferent family of machines.
Mapping COMPUTE!
We're organized sequentially, with the front section of the magazine devoted to material of general in- terest and utility. The following sections are devoted to specific machines. These are called Gazettes, and contain information pertinent to your special machine. Frequently, however, you'll find useful material in other sections (Gazettes) of the magazine.
Where The Sets Merge, Or Common Interests
All of your machines have available a programming language called BASIC. BASIC stands for Beginners All-purpose Symbolic Instruction Code. It's what is called a higher-level language. BASIC differs somewhat on the different machines, so you'll find some things in common with other BASIC'S and some differences. In practice, BASIC simply makes it easier for you to talk to your 6502 microprocessor. The 6502 sits at the heart of your machine. It and supporting "firmware" and "hardware" make your machine capable of doing what it does. In a nutshell, you feed your 6502 instructions that it can act on. It only acts on very picky little sets of numbers, and that's why you have BASIC. BASIC serves as an English-language like translator for you, taking your instructions in a pseudo-English format and translating them for the 6502.
Other portions of firmware contribute to your machine's features. Someone has already written a 6502 program that resides in your machine, inter- acting with BASIC, and passing out instructions to the 6502. This program (or set of programs) is called the Operating System. It is permanently inscribed onto a chip or set of chips inside your machine. Its permanence implies its generic name: firmware. Hardware characteristics also help define your machine and its capabilities. Memory is one impor- tant characteristic. Memory is your working space. It's much like the work area you have on top of your table. Let's assume you have a table of x size, and you're ready to start a project. You have a set of notes and instructions previously developed to help you with your task. Let's also assume that you may
not write on ycur previous notes, but you may refer to and use thern freely. These notes and instructions are much like cine kind of memory in your computer: ROM. Read Only Memory is memory that has a program already saved on it. The program doesn't go away when you turn your machine on and off. This, then, is your firmware: the ROM, or set of ROMs, where "permanent" programs, or sets of in- structions, reside. The number of instructions your Operating System can have, e.g. in part its complex- ity, is then directly related to the amount of ROM in your machine. Let's stack up these beginning "notes" on one side of your desktop. We'll assume that they take up one-quarter of the table space. We can use them always, but we can't stack anything else there.
Now let's add a clean notepad to our workspace. We'll call this our work area. Everytime wc come back to our des;k to work, we'll assume we have x amount of clean space to put our notepad on, and do whatever work we want. This "fiexible" work area equates to RAM. Random Access Memoiy is another type ol" memory inside your computer. Unlike ROM, which has a set of instructions "built- in", RAM is empty. It's your working area; the space you use for putting in your own information. After you put something in it, you can use it, reading from it later, and so on, just like your note pad. And like your notepad, you can continue to return to it, reading from it and writing to it. Until, of course, you turn your computer off. Your RAM is wiped clean when the power goes away.
Storage Media
This is why your computer has a storage device. Whether it's a tape cassette or a disk drive, it's there to save the contents of your RAM. Let's assume you've entered a set of instructions. We know where they are: they're in RAM. We also know that once the machine is turned off, these instructions will be era,sed from RAM. The solution is simple. Save them somewhere. When you want them bark, your Operating System will take care of reading them back into RAM.
Where Are Vie?
We've just covered the areas that make your small computer a truly remarkable and powerful device. It has a set of predefined features, controlled by perma- nent instructions, and aided by design features that always make it "act" the same way. Your calculator is much like this; and your microwave oven; and the host of other consumer products that are utilizing some form of microprocessor chip. The firmware in these devices is simply a set of permanent instruc- tions to a computer chip. But your computer has a whole lot more. It has RAM, allowing you work space to develop your own sets of instructions to your computer chip. Aha! Tremendous flexibility. And it has a storage device, allowing you to save the effort of your labors, retrieving them at will for u.se and further development. ©
Osborne Polishes
THE APPLE
and Publishes
THE GUIDE
The Appte II User's Guide by Lon Poole, Martin McNiff. and Steven Cook #46-2. $1 5. a
This Guide is the key lounlocl<ing the full power of your Apple Nor Apple II plus computer. The Apple II User's Guide brings together in one place a wealth of information for Apple computer users. It will tell you more about your Apple tfian any other single source.
Topics include: Applesoft and Integer BASIC programming - especially how to make the best use of Apple's sound, color and graphics capabilities. The book presents a thorough description of every BASIC statemeni. command and function. Machine level programming - although not a machine language programming guide, this book covers the Machine Language Monitor in detail. Hardware features - the disk drive and printer are covered in separate chapters. Advanced programming - special sections describe high resolution graphics techniques and olher advanced applications.
This book will save you both time and effort. No longer will you have tosearchertdlesslyforusefulinformation. It's all here, in the Apple II User's
Guide, thoughtfully organized and easy to use. -Appie is a Itademark of Ihe Apple Compuler Corporation
More Osborne Books for Apple Users
P!i
6502
Assembly Language Programming
by Lar^ce Leventhal Here's the booh ihat shows you how to program Ihe Apple in iTssemWy language. ' Wilh ils numerous relerence lables, ex- planattons and descriplions, this book is a major accomplishrnont Jfs by lar tlie most complete 6502 book to appear Make space on your Bookshell You'll want 10 keep Ihis one handy."
COMPUTE Book «27-6 ST6.99. 606 pp. □
Some Common BASIC Programs
by L. Pooie and M. Borchers Written m a subset ot standard BASIC thai is compatible wrth many microcomp jlers, ihis book coniains 76 useful and easy-lo- LTse programs- The booh explains how each program works, shows sample runs, and has program listings with remarks "If you want to do mathematics or slalistical programming on your cnmputer, Ihis book IS a must." ON COMPUTING Magazine Bcok i!06-3. S14,99, 200 pp. D
Practical Basic Programs edited by Lon Poole Here's a coireciion of 40 programs you can easily key m and use on most mrcro- computers. Practical Basic Programs is especially useful m small business appSi- calions. II solves problems in finance, management, and statistics. The book conlaina sample runs, praciical problems, BASIC source lisiings. and an easy to^ follow narrative to heSp you realize ihe potential uses of each pfogram. Book «3B-I. Si 5 99, Zm pp. D
An Introduction to Microcomputers Volume I - Basic Concepts Second Edition
by Adam Osborne The world s best selling textbook on microcomputers develops a detailed pic- ture of what a microcomputor can do. how it does what il does, and how it can be used in any practical environment. TNs IS the most comprehensive and up-to- date introduction to microprocessor systems available anywhere Book fi34.9, SI3.99. 320 pp D
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14
COMPUTE!
March, 1981. Issue lO.
Computers and Society
David D, Thornburg
Innovision
P.O. Box 1317, Los Altos, CA 94022
As R. Buckminstcr Fuller is fond of pointing out, synergy is the behavior of whole systems which is not predicted by the behavior of the parts taken sepa- rately. There have been two recent developments in the personal computer world which, taken together, have the promise of true synergism. These events are the publication of Se)'mnur Papcrt's long-awaited book: Mindstorms - Children, Computers, and Powerful Ideas (Basic Books), and the introduction of the language PILOT for the Atari computers.
Since this year's theme is communications, it is only appropriate that we spend some time looking at the communication between the user and the com- puter. While the mechanical means through which this communication takes place are worthy of exten- sive discussion, I want to concentrate this month on the nature of the language through which we interact with computers, since this also is an area of intense importance.
One might argue that there is little reason for concern with computer languages at this point, since we all have access to fairly powerful versions of BASIC on our computers. We might all agree that BASIC is not terribly hard to learn, and that there are lots of very exciting BASIC programs, and even that BASIC has become the dejado standard com- puter language for personal computers.
But even with the tremendous penetration of BASIC in the marketplace, I have yet to fmd any serious computer user (regardless of age) who really likes it. At the primitive level of programming at which we all start, BASIC works pretty well. But as we get more sophisticated, most of us fmd ourselves writing code that we can't understand two weeks after we write it.
Of course, there are detractors of BASIC who feel that languages like PASCAL are the solution. I must confess that I find PASCAL lacking in that h doesn't encourage the user to sit down and start writing some small part of a program, to play with the bits and pieces, and to then bring everything together later on. This is one area in which BASIC excels. For those who feel that people should be organized when they write a program, PASCAL (and C and other "serious" languages) may very well be the best choice. But what about the new com- puter user who wants to build a highly interactive program, or the child who wants to explore concepts in geometry through the experience of programming
rather than through playing a pre-defined "game" or sitting at a "canned" CAI lesson? These people need languages which arc interactive, highly flexible, extraordinarily powerful, and are easy to get started with.
LOGO And PILOT Are Two Such Languages.
While LOGO (as this is being written) does not yet exist on commercial personal computers, it has been the subject of an extensive research program at MIT for inore than a decade. Much of the research has been devoted less to the development of computer languages per se, than to the development of a com- puter assisted learning environment for children. The
...for some educators, Computer Aided Instruction has come to mean "computers programming children".
goals, aspirations and results of this work are the subject of Papert's Mindstorms. It is hard to im- agine any person who is intensely concerned with the use of computers by children who would fail to be moved by the sweeping vision implicit in Papert's work. Writing from the perspective of a maihemeti- cian who spent much time with Jean Paiget, Papcrt presents a variation on the Paigetian model of the "child as builder" in that he sees the need for children to have an abundance of materials with which to build things.
That the computer can be one such building tool is the cornerstone of the many computer literacy ac- tivities we see springing up around the world. But, for some educators, Computer Aided Instruction (CAI) has come to mean "computers programming children". There is much to be gained from revers- ing this process — and that is where the need arises for an exceptionally powerful (and easy to learn) computer language.
LOGO is a highly interactive language which contains a graphics environment containing something called a "Turtle". The Turtle is a non- Euclidian point (having both position and direction, rather than a position alone). The programmer can send mes.sagcs to the Turtle which cause pictures to be drawn on the display screen. Those of you who arc familiar with the Milton Bradley Big Trak are already familiar with this idea. To draw a square on the screen, for example, a child working in the Turtle micr-oworld might type: FORWARD too RIGHT 90 FORWARD 100 RIGHT 90 FORWARD 100 RIGHT 90 FORWARD 100 RIGHT 90 \
March, 1981. Issue lO.
COMPUTE!
HAVE WE
G0TAPR06RAM
FOR YOU Mm
Attend the biggest public computer shows in the country. Each show has 100,000 square feet of display space fea- turing over 50 Million Dollars worth of software and hard- ware for business, industry, government, education, home and personal use. You'll see computers costing $150 toS250.000 including mini and micro computers, software, graphics, data and word processing equipment, telecommunications, office machines, electronic typewriters, peripheral equipment, supplies and com- puter services.
All the major names are there including; IBM, Wang, DEC, Xerox, Burroughs, Data General, Qantel, Nixdorf, NEC, Radio Shacf<;. Heathkit, Apple, RCA, Vector Graphic, and Commo- dore Pet. Plus, computerized video games, robots, com- puter art. electronic gadgetry. and computer music to entertain, enthrall and educate kids, spouses and peo- ple who don't know a program from a memory disk. Don't miss the Coming Of The New Computers- Show Up For The Show that mixes business with pleasure. Admission is $5 for adults and $2 for chil- dren under 12 when accompanied by an adult.
Ticket Information
Send S5 per person wilh the name ol Ihe show you witi attend to Nalionai Computer Shows. 824 Boylston Streel, Cheslnut Hill. Mass. 02167, Tel. 61 7 739 2000. Tickets can also be purchased at the show.
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16
COMPUTE]
March, 1981. Issue lO.
As each instruction is executed, the Turtle first moves forward by 100 units, and then turns right by 90 degrees, drawing its path on the screen as it moves. The desired square thus takes shape on the screen. A programmer wishing to use squares quite frequently might wish to extend the repetoire of com-
... Children are asked to find the bug by "playing Turtle".
mands the Turtle uses by defining a new procedure which the Turtle then "understands": TO SQUARE REPEAT 4
FORWARD 100
RIGHT 90 END
If squares of arbitrary size are required, one might
write:
TO SQUARE :SIZE
REPEAT 4
FORWARD :SIZE
RIGHT 90 END
and then, anytime a square is desired, one would
type, for example,
SQUARE 47
to draw a square with each side 47 units long.
The value of using the Turtle environment in an interactive way is expressed by Papert this way: WoTking in Turtle microworlds is a model for what it is to gel to know an idea the way you know a per- son. Students who work in these environments certainly do discover facts, make prepositional generalizations, and learn skills. But the primary learning experience is not one of memorizing facts or of practicing skills. Rather, it is getting to know the Turtle, exploring what a Turtle can and cannot do. It is similar to the child's every day activities, such as making mudpies and testing the limits of parental authority — all of which have a component of "getting to know". One of the more valuable experiences for children in- volved with computers is learning how to "debug" a program with errors in it. Traditionally, we are taught that errors are bad. Papert shows that, by ac- cepting the inevitability of errors in programs, children can learn to analyze the results of the error and then learn to avoid the error in the future, and to "patch" it in the meantime.
In order to make the debugging process as meaningful as possible, children are asked to find the bug by "playing Turtle". The child then walks
The ATARI® Tutorial
CDi;FJTEn
Calligraphy?
Well, not really! But with the FONTEDIT program in IRIDIS #2 you can design your own character sets (or fonts) for tfie ATARI. For example, you can create a Russian alphabet, or APL characters, or even special-purpose graphics symbols. These special tonis can be saved on ^\sU. or tape for later use by your programs. FONTEDIT is a friendly, easy-to-use program: just grab a joystick and start designing.
■i.-i)X'"nnyi'r
FONTEDIT
J V h n /
With our KNOTWORK program, you can design patterns of Ce/ffC interlace, (a technique used by 7th century Irish monks to illuminate manuscripts). After you have produced a pretty pattern on the screen of your ATARI, you can save it on disk or tape. As you might expect, KNOTWORK uses custom graphics characters tf-at were created with FONTEDIT,
FONTEDIT and KNOTWORK are available now\r\ IRIDIS «2, the second of our ATARI tutorial program packages. You get a C-30 cassette or an ATARI diskette with our excellent programs ready to load into yourATARI.Best of all, IRIDIS *f2 comes with a 48-page User's Guide, which gives clear instructions on how to use the programs. The Guicte also provides detailed, line-by-line descriptions of how the programs work, (IRIDIS programs are written to be studied .as well as used.) Our Hacker's Delight column important PEEK and POKE locations in explains many your ATARI.
The User's Guide also includes Novice Notes for the absolute beginner.We don't talk down to you, but we do remember how it (eels to be awash in a sea of byfes and bits and other technical jargon. If you are new to programming, IRIDIS is one of the easiest ways you can learn how to get themost out of your ATARI. If you are an old hand, you'll be delighted by the technical excellence of our programs. (We are the people who have published CURSOR for the Commodore PET since July, 1978.)
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March. 1981 Issue lO.
COMPUTEI
INTRODUCING
COGNIVOX Series VIO-1000
A Revolutionary New
Voice Input and Output Periplieral
Higli Fidelity Voice Response Industrial Quality Recognition
PET — AIM-65 — APPLE R
COGNIVOX series VIO-1000 is a top-of-the-line voice I/O peripheral lor business and educational applications and tne demanding tiobbyist.
It can be trained to recognize words or short phrases drawn from a vocabulary of 32 entries chosen by the user. It will talk back with up to 32 words or short phrases. In disk based systems, response vocabularies can be stored on the disk and brought to memory as needed, giving an effectively unlimiled number of vocabular y entries. The quality of voice response is excellent, and It js far superior to thai of speech synthesizers.
COGNIVOX series 1000 comes complete and ready to plug into your computer (the computer must have at least 16K of RAM). It connects to the parallel I/O port of thePET. tothegame paddle connector on the Apple and tothe J1 port ontheAltvl-65. Connectors are included as required. Also included are a microphone, cassette with software and extensive user manual. A built-in speaker/amplifier is provided as well as a jack lor connecting an external speaker or amplifier.
Software supplied with COGNIVOX includes two voice operated, talking video games. VOTH and VOICETRAP. These games are absolutely captivating to play, and the only voice operated talking games that are commercially available.
Adding voice I /O to your own programs is very simple. A single statement in BASIC is all that is required to say or to recognize a word- Complete instructions on how to do it are provided in the manual.
In keeping with the VOICETEK tradition of high perlormance at allordable price, we have priced COGNIVOX series 1 000 at the unbelievably low. inlroductory price of $249 (plus S5 shipping in the US. CA add 6% lax. Foreign orders welcome, add 10% for handling and shippingvia AIRMAIL) When ordering, pleasegive the make and model of your computer, the amount ol RAtvl and whether you have disks or not.
In addition to COGNIVOX series VIO-1000, VOICETEK manufactures a complete line of voice I/O peripherals lor most ol the popular personal computers. Speech recognition-only peripherals are available for the 8K PET and the 4,K AIM.
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around the floor, executing each instruction in turn until the "fauhy" instruction is found. But doesn't this method for finding errors lead the child to "thinking like the computer"? Papert sees this ex- perience in a larger context. He says:
In my experience, the fact that I ask myself to "think like a computer" does not close off other epislemologies. It simply opens new ways for approaching thinking. The cultural assimilation of the computer presence will give rise to computer literacy. This phrase is often taken as meaning knowing how to program, or knowing about the varied uses made of computers. But true computer literacy is not just knowing how to make use of com- puters and computational ideas. It is knowing when it is appropriate to do so. While Papert is quite heartened by the growth of the personal computer industry, since this growth will
He likens BASIC to the QWERTY
layout on the keyboard— an
artifact from a time wtien
better things didn't exist.
result in children having ever easier access to com- puters, he is frustrated by the limitations of these machines and by the extremely strong penetration of BASIC into the marketplace. He likens BASIC to the QWERTY layout on the keyboard — an artifact from a time when better ways didn't exist. But what of LOGO itself? This language will not be forever locked in the University laboratory. Versions for the TI 99/4 and the Apple computer will probably come into general availability soon.
Even if LOGO, with all its power, doesn't make its appearance in the marketplace soon, I feel that many of Papert's ideas can be implemented today on the small computers whose capabilities he dislikes, through the medium of the language PILOT.
As normally written, PILOT interpreters allow the user to create spectacular text manipulation pro- grams (c.f , the article by Thornburg and Thornburg in the first issue of COMPUTE!). Recent embellishments have made PILOT a splendid language to use on computers with high quality graphics environments, such as the Atari 400 and 800. Those of us who use Atari computers can, with Atari PILOT, do many of the things Papert does with LOGO.
Those of you who are familiar with PILOT pro- bably think of it as a language best suited for creating text-based learning materials. My view of the language is far more open than that, because it is so easy to teach to youngsters. It has long been my dream to see the superb text manipulative power of PILOT extended to give the user similar power to
18
COMPUTil
March, 1981. Issue lO.
create pictures. The Atari PILOT is the answer to
this dream since it contains a graphics package that is, in some ways, very similar to the Turtle graphics of LOGO.
For example, an Atari computer user running PILOT might draw a square this way:
GR: CLEAR GR: DRAW 25 OR: TURN 90 GR: DRAW 25 GR: TURN 90 GR: DRAW 25 GR: TURN 90 GR: DRAW 25 GR; TURN 90
As each instruction is carried out, the square begins to take shape on the screen. If the user wants to draw lots of squares PILOT allows one to create a "module" as a deferred program. By typing AUTO at the command level, and then typing:
•SQUARE
GR: 4(DRAW 25; TURN 90) £:
A module (SQUARE) is created. On leaving the AUTO mode (the AUTO mode automatically places line numbers in front of each statement, thus keeping them from being executed Immediately), the user can draw a square by typing:
U: 'SQUARE
in which U: is the USE operator found in all versions of PILOT.
My reasons for giving this particular example are two-fold. First, it shows the similarity between the Turtle graphics of Atari PILOT and that of LOGO. Secondly, it shows that PILOT can be used in an interactive mode which combines deferred pro- gram segments (modules) with immediate execution of commands.
Can (or should) PILOT replace BASIC? I can
only answer by saying that, on the Atari computers, it has for me. I find the language much easier to learn, much easier to use, and capable of doing anything I have ever wanted to do. One of its major features (especially important when working with children) is that a PILOT program can be read by someone other than its author. This is rarely the case for large BASIC programs.
Finally, while most users will want to use PILOT to write self contained programs, I am very happy with the fact that the Atari implementation of PILOT allows the user to interact with the language without having to write 'Tmished" programs. As Papert has shown, the value of "playing around" with an interactive language can be great for all users, and especially for children. ©
Editor's Note: Atari PILOT is not expected to be available until late spring. Check with jour dealer for more informa- tion. RCL
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March, 1981 Issue lO.
COMPUTE!
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COMPUTE!
March, 1981. Issue lO.
Editor's Note: Although Richard refers to the PET in this overview, I recommend this article to all who 've expressed in- terest in machine language. RCL
Taking the Plunge- Machine Language Programming for Beginners
Richard Mansfield Philipsburg, PA
If you have been using BASIC for a while now, you can probably go in and out of STR$ and VAL and there is no mystery to ON GOTO anymore. In fact, the only strange BASIC statements at this point are USR, SYS, and PEEK and POKE. They are gateways into Machine Language and that is still an unknown area. Take heart. It is said that people who first learned programming using Machine Language (M.L.) can find BASIC confusing,
In this article I will discuss aspects of M.L. pro- gramming which were unclear or difficult for me when I went on to learn M.L, after a fairly complete grasp of BASIC. I had seen "assembler listings" in magazines with their usual warning that the numbers must be entered exactly or the program could not work. And the numbers themselves were in HEX — 7 and 10 was OA! It seemed difficult. It really isn't that hard (but try to explain to a non-computerist that BASIC isn't that hard).
The first thing to do is to get a good book on 6502 (our computers' CPU chip) programming. There are five or so, but among the best are "Pro- gramming the 6502" by R. Zaks (Sybex) and "6502 Assembly Language Programming" by Lance Leventhal (Osborne). You can ignore such information as signed binary, floating point, octal, hardware and input-output chapters. What you want to learn is the
meaning of hexadecimal and binary — two new ways to express numbers.
"Machine Language" means that you are enter- ing statements in exactly the way that your 6502 pro- cessor will see them. By contrast, a BASIC statement such as LOAD represents hundreds of M.L. statements which have already been programmed by somebody at Microsoft and frozen into ROM chips inside the comp Jter. When the computer (always scanning and waiting for carriage returns) finds that you have typed LOAD, it has a list of addresses and chooses the one associated with LOAD and jumps (JMP it's called) to the address in ROM where the proper sequence of M.L. operations is set dowr. This sequence is like a subroutine. And BASIC- itself is nothing more than a huge web of thousands of M.L. subroutines. In the PET, for example, if you want to jump to the subroutine that sends the number in the 6502's "accumulator" (defined below) to your screen, you type SYS 65490 and the com- puter is thrown into its M.L. mode and told to start doing the task v/hich begins at the 65490th memory cell in it's brain. That is near the top. There are maps of the computer's memory cells.
A Simple Map of the PET's Brain
0 to 1023 — RAM (you can change it's contents), but used by BASIC to store addresses (called pointers), temporary data (such as what you type in from the keyboard, called input buffer), temporary data of its own in a stack, and all manner of reminders to itself about whether or not the tape recorder is on, etc., (called flags). So, if you tamper with these memory cells, you might confuse the computer enough to send it into an ondless loop within itself and you cannot communicate with it again until you turn off the power and farce it to reset (get itself together). 1024 to 32767— your RAM to use for BASIC programs, or M.L. programs which you put together. Unlike ROM, these cells can each contain any number from 0 to 255. ROM is frozen with its various numbers carved in forever. All PETs start their RAM here , but if you have 8k then you can only use RAM up 8000 cells from 1024.
32768 to 33791— the cells of your screen (40 column screens).
36864 to 45055 — space for you to add new ROM chip:; such as Toolkit. 45056 to 65535— BASIC itself, along with the computer's instructions about interrupting itself (if you should press STOP, for example), how to run the T.^''. (CRT or monitor), how to talk to the peripherals (I/O), and other housekeeping chores (called the operating system). Far more detailed maps are available to tell you exactly where things happen inside. See back issues of COMPUTE! for Jim Butterfield's exhaustive maps for PET (i.ssues #1, #6), APPLE (issue #2), and others (issue #2).
March. 1981, Issue lO.
COMPUTE!
21
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COMPUTE!
March. 1981. Issue lO.
The Monitor and the Three Kinds of Numbers
It is important in learning M.L. programming to grasp a distinction between the three ways that the computer could see any number. Depending on the context, it will think that a given number is either a datum, an address, or instruction (a task it should perform, such as fetching something). To illustrate this distinction, we can construct a simple, but very common, M.L, routine using the PET M.L. Moni- tor. (If you have another computer, the addresses where you locate this experiment and the address of your screen RAM might diiCer, but all our 6502-based machines use the same M.L. instruction set). To enter the monitor, we must SYS to any ad- dress in the PET which contains a zero. There is always a zero at address 1024 so we can type SYS 1024 and the PET will display the "registers" and the cursor will land beside a dot, indicating that the monitor is available for our commands.
Let's ignore the register, and simply notice that the fourth number listed is under an "ac" which means that, at this time, the "accumulator" in the 6502 chip contains this number. For a long time, I wondered which addresses in the PET contained the accumulator, the x register and the y register. They are actually unique and not part of the RAM or ROM memory as such. These registers are stopping places for data as it streams from one place to another, from one actual memory cell to another. But on to the experiment.
We will put the letter "A" on the screen. Following the dot, type:
.m 0360 370 (this asks for the numbers between
these hex addresses) Then, when the numbers appear, type in these new numbers right over the ones on the screen;
.0360 A9 41 8D 00 80 00 (we have written a complete action for PET with this, so hit the return key to let the monitor enter these new hex numbers in place of the old ones). If your monitor types a "?" then you have made an error where the "?" appears on the line. Try again.
What have we got here? When the PET is told to start with the instruction A9 it will load the next number in our sequence into the accumulator. That will be the 41. Then it looks at the 8D which tells it that the following two numbers (00 80) are the ad- dress to store what is in the accumulator so it puts the 41 at address 8000 (which is hex for the first cell on the screen — and an "A" will appear there. How did 00 80 get changed into 8000? You just have to get used to it. An address is read into the computer LSB (least significant byte) first, followed by the MSB (most significant byte).
The last number we entered was the 00. This is hex for 0, and it is called a "break" which was the way we got into the monitor with our SYS 1024. In this case, when fmshed printing our "A", it will come upon our break instruction. Now type: .g 0360
(which means go to 3060 and do what it says there). The "A" will appear and the monitor will come back on showing its registers. Notice what is in the "ac". You can print any other letter by increasing the value where the 41 is. To return to the BASIC mode, type an "x".
This example, so simple, is just how the com- plex tasks are performed by the computer — one thing at a time (but fast). Organize enough of these segments and you have BASIC, or FORTRAN, or any other "higher" language. Look at the two OO's we used. They represent two different types of numbers which are context-defined in the computer. Since the first 00 followed an instruction (8D) which said put the "A" here, the computer knew that this 00 was the less important part of an address and the next number it found would be the MSB of that same address. Having finished that job, it asks, what next? The next number can never be an address or a datum. It must be an instruction to the computer, so the 00 in this position is the instruction "break." A number can only be cither a datum, an address, or an instruction. Of these three possibilities, the com- puter knows how to interpret a number by the "syn- tax" (the relative position to other numbers in the sequence). This is exactly how we know what some- one means when they say "TOO TOO" on the phone, as in "My little girl is two today."
So, our "41" can translate three ways: datum — the actual number (or what that number means in a code, "A" in the ASCII standard translation system); 2. address — the 41st (65th in decimal) ad- dress cell in the computer; 3. instruction — please exclusive — or the number located in the cell pointed to by the address in the first 256 bytes as offset by the X register. (Before you are alarmed, there is very little chance that you will ever use this particular in- struction with this addressing mode in your entire life.)
M.L or Assembly Language
What we have just done is the most cU'im-ntal level of coding next to flipping switches for each bit in each byte. We have entered our code a byte at a time using hex humbers. But this is slaw. And, since numbers are so abstract, they arc hard to remember. The term "mnemonic" means "memory helper" and this is the next step up. Simple toggle switch or hex programming is usually called "machine level" or "machine language" programming. If you use a three-letter mnemonic instead of A9 to help you remember that this loads the accumulator, things will be easier. LDA means load the "ac", BRK stands for break, and STA means store "ac", and so forth. There are 55 mnemonics, one for each task that our 6502 can perform. However, some of them arc so rarely used that you can easily copy down the main ones and learn the strange ones later if you want. Most everything can be done with about 20 of them. or course, the computer will not understand
March. 1981 Issue lO.
COMPUTE!
23
SPECIAL
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INTRODUCING OCT DA OD IT OR ROM rC 1 nMDDI 1 CASSETTE The PET RABBIT contains high-speed cassette routines, auto-repeat key feature, memory test, decimal to hex, hex to decimal, and other features. Coexists with the BASIC PROGRAMMERS TOOLKIT. Works with 3.0 ROMS (New) and new style cassette deck. Cassette versions configured for SI 800, S3000, $3800, S7000, and S7800. (3.0 ROMS only| Cassette and manual ~ $29.95 ROM version configured to plug into P.C. board at SAOOO. (Specify 3,0 or 4.0 ROMS) ROM and manual -$49.95 FREE ROM RABBIT with purchase of 8K PET and tape deck. SPECIAL - ROM RABBIT and cassette deck --only $134.95 |
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MACRO ASSEMBLER >^ AND -V V' TEXT EDITOR ^^^ Macro and conditional assembly, string search and replace, 10 char./label, AUTO line numbering. MOVE, COPY, DELETE, NUMBER, and much more 20^- commands, and 20-1- pseudo ops, PET cassette version (ASSM/TEDI - S49.95. (Specify 2.0, 3.0, or 4.0 ROMS.) PET disk version (MAE) - S169.95 (Specify 3.0, 4.0, or 8032) ATARI cassette version with machine language monitor - S53.95 FREE ASSM/TED and ROM RABBIT with purchase of 32K PET and cassette deck. FREE MAE with purchase of 32K PET and disk drive. |
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TRAP 65 TRAP 65 prevents the 6502 from execulting unimplemented instructions. Have you ever had your system to crash on a bad upcode? This is a real machine language debugging tool and time saver. Also useful for teaching trap vectoring and extension of instruction set in schools. 3% X 4% printed circuit board which plugs into 6502 socket of any PET, APPLE, SYM. Only S149.95. |
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ATARI M.L. MONITOR Load and save binary data on cassette. Display and change 6502 registers. Will coexist with BASIC. Monitor uses the screen editing capabilities of the ATARI to allow easy use. Cassette and manual - $9.95 (specify memory size), ATARI MEMORY TEST When you purchase a new ATARI or add on new RAM modules, you need to be sure that the memory is working properly. (Remember, you only have a short guarantee on your memory!) Cassette and manual - $6.95. |
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TINY-C FOR PET An adaptation of the TINY-C interpreter sold by Tiny-C Assoc. Useful for learning a modern structured programming language. Diskette - S50.00. Owners manual - S50.00 FREE MAE and TINY-C with purchase of 32K PET, disk drive, and printer. |
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COMPILERS Graphics Drawing Compiler for PET and SYM. Works with Macro ASSM/TED. The GDC is composed of a number of macros which emulate a high-level graphics drawing language. In addition to the macros, GDC provides some very useful enhancements to the ASSM/TED. Manual and Cassette - 529.95. Music and Sound Composer for PET. Works with Macro ASSM/ TED. The MSC is composed of a number of macros which emulate a high-level computer music language. In addition to the macros, MSC provides some very useful enhancements to the ASSM/TED. Manual and Cassette ■ $29.95. |
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APPLE PRODUCTS Macro ASSM/TED — includes manual, on cassette — S49.95, on disk - $55.95 Apple MAE - similar to PET MAE. A powerful assembly development system on diskette for 48K APPLE II or plus. (Requires license agreement) — $169.95. PIG PEN - 100% M.L. word processor for use with Apple ASSM/TED. Fast text formatting, vertical and horizontal margins, right and left justification, centering, titles, foots, shapes, etc. Manual and source included, on cassette — S40.00, on diskette - S45.00 Apple Mail List System. Provides sorting on zip code or last name. Approximately 1000 names/diskette. Manual and Diskette - S34.95. |
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I/O KIT PET 1/0 Experimenters Kit. Allows easy access to IEEE or user port for the construction of external circuits. Kit - S39.95. |
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24
COMPUTE!
March. 1981, Issue lO.
LDA. It only reads numbers, so you will use a pro- gram which lets you emer the LDA, but pokes A9 (actually it hands the PET a decimal number and BASIC takes it down to the binary level for you.) The program which gives BASIC a translation of your LDA is called an assembler, hence assembly language or assembly programming. The terms M.L. and assembly language are used inter- changeably, though, and both refer to an entry of code in the same way that the computer will later follow it, byte by byte.
Using the M.L. Routines from BASiC
In many cases, you can use a routine in the BASIC code by finding its starting address with a map and then examining it with a disassembler (a program which looks at the raw numbers and translates them back into mnemonics). Then you can just JMP (jump) or JSR 0*^™? 'o subroutine) from your M.L. program directly into BASIC'S M.L. code.
If you are programming in BASIC itself, life is simple, but execution of your program can be too slow. To use our example, if you wanted to print an "A" from BASIC you would type! PRINT "HA" and the tompuler would put a 41 into the ac- cumulator and jump to 65490 where an all-purpose routine for outputting a byte is located in the BASIC ROM. You could also do this with an M.L. routine by typing: 0360 A9 41 20 D2 FF 00 (The 20 is JSR and the FFD2 is hex for 65490).
But this, too, is slow. After landing in the BASIC ROMs, the first thing that PET does is a jump to another address where it determines that you mean to send the "A" to the screen and not to the tape or a printer. Then it flys down to a "vector" at address OOBO which is rather like a corner shot in pool — when it gets here it just picks up another ad- dress and goes back up into ROM memory pretty close to where it jumped from. And so on. Since BASIC must do all kinds of jobs, it is more general than any routine you program in M.L. yourself. It has to check many parameters before acting to send your "A" to the screen. So, often, you will want to save time and code in M.L. yourself. Using routines from the BASIC ROM also requires that you know what these routines expect as preconditions. That output routine will print whatever is in the ac- cumulator, so you must have loaded it already with the character wanted.
To give another example, you can print a large decimal number to the screen (as in scorekeeping during a game) by a JSR to CF83 (in BASIC 4.0), but you must already have placed the LSB of that number in the X register and the MSB in the ac- cumulator. If you want to experiment with this, go into the monitor and when the registers show on the screen, type over the number in the "ac" and the number in the "xr" with the MSB & LSB of the number you want to have printed. Typing return
will change these registers. Then: .0360 20 83 CF 00 .g 0360
What you are doing here is entering BASIC where it prints line numbers on the screen during a LIST, but you are going in and out of that particular area without using any other aspect of that code. Trying to set up this sort of printout would be un- necessary and time-consuming if you tried to do it yourself. So, in this case, we are happy to "borrow" some already programmed M.L. routines from the BASIC ROM.
M.L. or BASiC— Whicii Is best?
Often, BASIC is best. It is easier to program and easier to debug (fix errors). Whole tasks can be left to the computer which you would have to carefully program in M.L. code. And BASIC uses a language which is crypto-English. At least lor the beginner, PEEK is easier to relate to than LDA.
M.L. code, when you RUN a program, will often enter never-never-land — an endless loop which you cannot get out of without turning off the computer and destroying the program. There are "warm" resets which you can add to the PET which will exit such a loop and leave your program intact. One helpful technique is to fill the memory area that you are coding with zeros before you start. Then, if something goes awry, you might land on a zero which, as a BRK instruction, will safely send the
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COMPUTE!
27
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28
COMPUTEI
March, 1981, Issue lO.
Computer Communica- tions Experiments
Mofvin L De Jong
Department of Mothemotics-Physics
The School of the Ozorks
Pt. Lookout, MO
I. Introduction
This article describes a RS-232C interface circuit for serial input/output that can be used with any com- puter peripheral that uses such an interface. In this instance, the peripheral is a modem (NOVATION CAT) that can be used to transmit and receive data over telephone lines. Many modems require a RS- 232C interface, hence the need for the circuit which in turn uses a 6551 ACIA (Asynchronous Com- munication Interface Adapter). The purpose of publishing this work is to find one or more persons who would be willing to experiment with computer communications over telephone lines. The article also describes some very simple software that can be used with a modem to transmit and receive messages over telephone lines. Later, more sophisticated load and dump routines can be written to transfer large amounts of data and/or programs from one user to another.
A true confession is that I am a beginner in the area of computer communications, and I would like to try some simple experiments before I fork-up a big subscription fee to one of the networks, only to find that my equipment or my understanding is inade- quate. If you can obtain the necessary equipment and if you are in roughly the same position, write me a letter when you have said equipment operating and we will try to arrange a time to try our hardware and software on a telephone link. I might add that the software and hardware described here have not been tested, except in the "TEST" mode on my modem, in which case everything worked properly. I am aware that my routines are simple and slow, and I would welcome suggestions for improvement.
II. Circuits And Things
I sometimes wonder if there are any hardware en- thusiasts like myself out there. You might let your editor/publisher know of your interests. My hardware fan club seems to be the null set, judging from the amount of mail I get. But here is another circuit even if no one ever builds it. You can always buy an
RS-232C interface anyway. The circuit is shown in Figure 1. It consists of three integrated circuits, a 6551 ACIA, a MC1489 RS-232 line receiver, and a MC1483 RS-232 line driver. The latter two circuits change the RS-232 signal levels to TTL levels, and TTL level signals to RS-232 signal levels, respec- tively. The 6551 ACIA operates at TTL levels (5 volts is logic one, zero volts is logic zero), while the modem operates at RS-232C signal levels (see Michael E. Day's RS232 Communications in COM- PUTE!, September/October 1980, page 26). The power connections for the MC1488 and 1489 devices are given in Table 1.
Table 1. Power Connections for the RS-232 line driver and line receiver.
Pin 7 = GND
|
MCI488 Pin 1 = |
- 12V |
Pin 14 = + 12V |
|
MC1489 Pin 14 = |
+ 5V |
Pin 7 = GND |
The connections to the left of the 6551 ACIA are made to the user's microcomputer system. Most of the signals are standard 6502 system bus signals, and require no explanation. Thus, address lines A0 and Al are used to address the four registers of the 6551, and are connected to the register-select pins RS0 and RSI. (You will probably want to obtain a specifica- tion sheet from either Rockwell or Synertek when you get your 6551; in fact, I advise you not to build the circuit without a spec sheet.) The data bus con- nections are shown in Figure 1 , as well as several of the 6502 control lines (R/W, 0,„ RES, TRQ). A 1.8432 MHz crystal is also required. Still referring to the connections on the left-hand side of the 6551 in Figure 1, we are left with pins CS0 and CSl, the chip selects.
.M|\'AT10V CAT MDDF.M
Figure I. Circuit for the 6502-to-RS-232C-to-Modem interface.
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ipIitrdccLmcnUEjQn :oncijr.in| ticu f (fUiTmiiuni mJ <umplei L'rim oilier* iu ipKJHciil.i]] Of) iptcf l,ATAR.Wn|tiiirii.:4ki bi>({'i ^iweBScai.pf^tiuiuAEeattiUbtaoa aTaRI, P£T. .U»lrilldAikTErcai'Bcl]uNtalbSuJu«-|Uil(«l4l>ldout(kd<fi.ul} fMBpalitiIr}'di^cl1r. Addi- 1 lUndiil (I&U !»nuE} V CP'M Flopn iliikl. fia i)tEnni niniuni lasls MfiASIC
BUSINESS and UTILITIES
MAIL l.t»T II (Appit ■nil .Mmli SlirdiikHIti onJi!
Thu mtr-i IriitH''^ ctatitm nr» iivludn lutt alphihcEic iirvd iipi dtlinrdcDdr. (|i«»l munrDr fipCodt TtriifiBlimitlorniaEmUt™! iHui MW«ntT!»iti>xlid<iithtf NodHSiir oi Aroit IXlli ? I; o'
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LtMAIl. MST II
<irh«vd PH:ki|.c fot IJ'F.tl
TKXT SPITOR I (Ulter Wrl(«r|
An r*!> IH uw. liB( ^n-miifij i(i)i rfiuT *hij,ii pts>viJr<i laiiabi (lulril for compDiim Lnlri^ fniE it qiiEic capabk dI Jiandlin| n
P»:t($ONAL FINANCE SYSTEM (ATARI oolr)
FTS t> a uoiJr duticwtRiocisiird irslm tDtnisincd ot lOprofj
incliidt i W> !T»B.iicii™ ^pKU}. fail aesfn, ;s cpii iiponi. chnk'book b«Ui>nni: bv niph c^oiiini «u3
Phcc: SM.H CuMllr^'ill.H IXikrIlr
nr v.bdEti) mini tifhiplf pulitrtph ladnjnf Ttiii irit ntiloi li. ninlh h IkfiTf jvCl Atkibtblr Icf 4ilc<Mitpuliii.
F^ricc: tM.99 Hdctk I deiiiHii la «|iauc uid iicipLr^ jtnir pcnout f runm Ff*ium (Mini, dala frCfidll bj rcaailk,. cwU DC IM.>h: ii^iunuj pnnlicif ^1
6 :jh auciic ii aTaM DOS Z.
FISDIT INorth S«»r oolj) PTf«:$if .»
Thtiu i ElhrR-tB-OTE pfa|T■ffv'■^Kh minitOM infiOfPi^m" #«c™b*bT krynoiili ofltrcclrl^l: FWiorul ttt l»»i ^*m*>. Ctxrirmr cuJlil iiifLrvbeniliiidlllrfEr™™ Jt| tMf»nnt»rElrki.rtrP«diJbw«m.WI In addiMilo kcjwoiilicmishei, ihnekf* birihdaj. «n iitk«ur> wd irP^il^KiX »ali*«rct Ihr pftwndlm«dt «»d pppomcBicnJ icaiikn !« Ita HnunrrtiaJ tciMdl KtfeiifXt (ttofdi arc Konwd bf a ui|k krr>crd ct ^ crnvtrrn-trcind fac-^v ihin krri™")^
PTfcr:tLf.H
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PTf«:*II.« a BASIC ptDpuni.uiddLipli.)i'i!li< TilrHtnofihrprofriPiiin ) nunib«(i«l *hKh tiU-iauiliiuddirfcTEncci DczuT. COMPAHl; iS« more turitri, and lodeiily IdcnEify Eht chtrt«i Rii>dr djr
DFILEINpHti.Stiiranl}^
Thii handy prcifiini aJlonai pworih Sew ukii ii>iKuri:«jTi »i • uubl, b(iimjilaEn DFlLt ii cuy 111 id upcrul uk It *■
COMPARE <NonlL SuroolT)
CQMPAKE naunilediik uEdiEj v^laarr packXp whitti^ bnn, lhtltri|thl.iritfrfHlprihf ntunbcrolttalcmfrt linn,
pniDin IJit LHT lot* inline irniontoI"hii wfi*u? to vrnf' ini dnrlopmrnt
COM PREJ^S (NPhh Slpr only) Pftct: t11.«
COMPRISE 11 iunifc.^ Ilk iji>Jiiypfi^ftirviahK*T*a*»*fi»llM»uiaetM*l>if*C«i*d|»f«wa*Jlf)SEM«ku*lrmi[ntifiDmSorlh& BASIC ivorimi. Ttit Knitct flk 11 procaKd wk knt ii 1 %rm. Ehiw p^iEAiiiiiHt ritj taitt fnetfuiiM W b# compiiiii^d mini £>r]( t invail ■ini>ui>t of ciHnputcr iMrrMf?, Flk ooapftiMta of ZtVWit Mf (wmiaaly afluncd
GRAFIX (TKS-W ob]>) Tiltt: SILM CbkHt/IU.M Dbkcllr
Tb.imciqiH' prpfifn iUmi jisj Iei buT; cmEc |rmpttK7i dircrEIr IrdOa lh«1lt)tMvd. fott "dn.»''''>ixic TifUJC isiof tbc Tftipini'l n- WtlVLvtfurm nnuciii QiifcUicEisiirrusudc.i1 ii ■.ulomaliollji atifiMdcd EOjesU EaSIC p[i>fruE u 1 it.-ia[ ''I.'iit4c . Dra* I "hi?- n ftcr'*. call i| Hl«ad cSen pnn: n finn roui iprnsraai uvni PKIVT HS' iSii lII >tf)' cu> *i!i to ZTeUc and u^c (Tiph'Ti
TlbV (TR&JO dbItI Price: ltO.H Caorllc'SII.H Dbkcllr
TEDV n an aucmb^ tanfufr jHOfrain vhith alidivi Ttni iCi wiuTititi the Lnci in jtiHir BASIC pnrfcanii. TIDY altc rmp^rt v" nRnuii> ipa^^n jj%d RFMark tlalrmentik Thf (null ii a EMii|1>*Ci*d lASIC profiiJii <*tvi<c:K LiMi mocb kii B>cnwryspKTiBd nnvirk iijn.fKriil) Utl" Ohc Uiajinl. TIDY irnuini In nem^T. )C<u .mtl ki«d tAI nun^ ul lASIC prctfjuni i>iE}K>ul bivin| id rtloid
STATISTICS and ENGINEERING
DATA SMOOTHER (NoL ivailibk f«r ATARI) Prin: SM.VJ CnK(((/SI4.« Dbkttc*
Thn ipeiiil dala imcuLMeij: ptE^llim rrllr »utn) tciapiiily ilHUt JMful mlcMtridoii Iram rcii* buiinni ■■twiri1iln«siP| daU "bub ur equally i.pKnl' Thcicruale (EaEurn (^Dieiin d«|IH iAdi rir|« i>( riS.iiwtll at imnolhcd rm and KCOnd d(Tiriiiv( uEcuUliun Atio mduJcid ii auEiLrmjEti: pd^l1>(1| Oj' ibf lltpul. dkll aral IFTiM^ESciJ IctulEI
FOURItJl ANALYZER (At altabit (or til eonputtn) Prtc«: SI4.« Cnrftt/f tl.t5 VMAttu
Uk ihr'; jKuiiajn luiLuniEw tiit fiei;ucrjct i[Mi:ira ailmi:cd duiaEion ii|ruh Thrncfrin Inturn auicmiit Ktl^nt ^luj plaiEinf ef lb* iti-tmi dala add Snjlii PlttfikUl tppliniiiaii-i incEjdtEbf aratjitiol nxTiplitalid pallfintjn huih Tiddl liElR1'prii4.i. cciniinijrKt' lii^m lEid baiincvi
TEA CTraeufcr FaDdJoa Anaijici) Price: Sl4.« CnKtIc/S23.« DbkrfCt
fumiujii thru itipaau id pulicd iaputi. TFA ii 1 cnajw mt>dirRciiii«fi cf FOL'illEP ANALYZER *nd opKiatni u fnimccrLiii w>>cn((d dMj.b«l •erijilDf-fiifqufncTjiiotuvril ai diticdiEinf rnij^n. Whetnt FC^JRIER ANALYZER it dniirv^ fm nluutHmal lAd K^tftiifhi btt. TFa 1.14a tcfixiKrTni ek>I AitaLatk lot all (tnip^icn
HARMON IC ANALYZER (Avillibk Im ill compytm) tikt; SU.tS C»wri(/;zi.f$ Dtakric*
HARMr'i'iiLi. ASAiyZFR -u, iktifiud (or ibr irciEiuT inaliiii ul icrniiiir ^t^rt<?rmi Fewtfn. incbjiSf tilt fdt tcnnaiion, «d>iin| *f>J lEMattrfirif'-aJ u ocLI ai dala hnd iprdium ptollinf Ok pttlKulallr uB^guC lkril:ir ii. |)<*1 ibr iBmi data need noCbr it^tuJIr ifALedoi in order Thconfina] iIiej 11 KMicdusdirubKipliiK intcriwItiKiniiuvnl tccrtA'ritrdtli Eik'n't'cdbii i!h ti r
FOL'atJiR A^'ALYZ£R.TFAuld HARMOKIC ANALYZE tC Mar be puEChkted ICtnhff Th ACCFinbincd pri«af 144 45 lElirK u- IWtftl «niJ Ije »5 |:hr« diitoEnI
Pric«:StV.93 CasKttt/SU.H DbkrEtc u«r*i "iwJjnaErLir'curstfitiifii piofi-a^. Fuurnm- (lire Ikterrul libriEi' of riiiini fkirfEioct: diEa rditint: , fi>ittii.lii>ri<Mrru:iiini, c^cJandnucimDrt In addl- uEity Ihe tiXnernlCMfit^laniilt ■T^j'dlta ui4t]rli.«iiU}fl-
REGRESSIO.^ I (Aviitabk for all conipu1cra>
REflRt^^lON litiLniiiLe j.rd FicriTtiarulJ; vrr^jlieDrc dimEn»[Fi^al kl (llrfr ft bllh acstuaci; an autDmalic decree dftcrminallon opEJeH; ail iUlpmtlit itt* ind Wi^r TiloKini; a i4«Ei|lK«l analpli |ri: ilanla^d driLi i»n, (»cw fill m4j bf (r Irf ■Hhcut Kwilmni bhe dan. PEtiHt55lON I u.
RECRtii&SiaN II (PARAFIT) (Avtilibit ri>r all compnlrn) ?tkt- St9.«3 C*umi«/SU.h Dhktiic
J'ARaI II III itUiiitd to handk Ihoir aui in #1»ib \M p*nmttm ire i^nboMM [KWt<lT n^nJinr«i>t] m |br ritiBi ri;n.-liDn Tbe ^lxtt itmpl^ iitriili \Yt lunclicul lanB. UKtudinf IJW pftruonm (Aid, AfU, <nc.]i|i1 ftot mot^ BA5fC ttalcrarat Iinn l^la and ttiuJ:i mjr M iUTLruUtcd iaJ pj«iid u mlh REGRE^STOS I Uk HECHtS-SIOS r Tor potrnomul muni.fndS'AIAFIT fen lh«e
MULTILINEAR REGRESSION (MLR) (Avalltbk for til contpHtcn) i^kr:S(9.95CMP«iit
MLRit ipialfiiiHulHrtiititpKkatEliCKutityaPtiiaiaKiiconEuniniiBOH cvort liinnrh indn^ndnu itmMn B?u4rit>r'riM'ni
IBi ttw htiK r<4ifi4)ori.uWUiio(i.. ihii pi:[>fj»ni ilto p<r>td« my tii uh dtia mtir.iiMifT.rtt'r>t^il tnd niiHi fuaciuwti In addi
l««i, Itwttiff mty tn:trrotKt llHicriiitKHi b) ittpphnil >a]uci la ihr imiTfwniimi iih^Hn Tht numbtr pI ttt4Nri»n4:daia lur h
Lmii«d orJ]! b) ii« *itiltbk RwiMn.
KtCiJlli!HON t. II u«d MULTIUWEAH KtORC3AIOf< ru> bf pi'"'f«i«'' itieil-fi iw IM »1 [iMrt iaiwcltii m WI « iitiif*
cki!tiiin>.
BASIC SClENTtHC SUBROIiTINtS, Volum* 1 (Not avallibk (Or ATARI) DYNACOMP II IJHHI.-IMH.C dunituicr [o> ihrwri*«r< krjrti<^ibf t(.i a^S/rSrw^ii^r a^ftfoLitj. (i« tht KYIb^MfCriO' HiU jd'etEiKCrifnE in SYTL mifUilK'. Jinwi* m 11 ThtV HLbroutinci bavc Scce uvmbtnl ucoidini la chiptef . Isduded Hiiti erch n^llKtion ii ± ircnM profram liliicti irl<CEi knd dcrrefltlfiiti rKh lubiounnr. Cplktuar »l: Chgpim 3 Wd ^ Dma anij fui;t>on plEillinj. (OErplel »AftaUn
CalltEiion H\ Cctaptn *. Mxirii atid ittiM ^iwjihc^ni
CDlbmior 1' Chicnm 5 xnd 6 Rind«n nvnbtr imeriiw!. tCKi ^mnalniltpai Pim [W coHnrtisn. (14 95 CuK9.Ef/SI».Sl IMilnx All ibm (ciIlKEimit 4ir*iiil4bE< t»r I!<l>] itb-tr (jiiriinl and t4l.«t l^ihM dtikMEM)
. SA51C itmiiflc SaUVMimn rn^v-r I ii ivulabtr rio<T' DYNACOMP 1-x
ROOTS (AktJltbk for rII compalm) Piitc ».99 CasMm/S13,»S Ptokrtu
tn « EbEihcil. KOars itmiiluDEO'iiir.i^tcnm.DciLEliteziiDnof i-poljr-^n^IhtMPi rul corffKrcmi Tbctc -a m litril onibt dnrn ol EM [>al)iuoiji!. aj'.l t^ojic ib« prtxiinit n iicnliit. LSt ^L'lTjTK'y ti ftnTi^li 'cry (cod So in^Eu] f-joia arc rrquircd ai inru'. a.-M iru ."AEtuUi-n: rAXi tit ibK::itiied h*ii into iht po^ritomid a-.d' tS< rciidLaJi djpla)cd.
w/b>F RiiHkdeiChil
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30
COMPUTEI
March, 1981. Issue lO.
The chip select pins must be controlled by the address decoding circuitry in your microcomputer system, or else you must add your own address decoding circuitry to produce the chip select pulses. Since I have an AIM 65 system, I used one of the device selects available on the expansion connector, namely DS9. This signal is active at logic zero for any address in the range $9000 to $9FFF. It was tied to CSl, the active-low chip select. If CS0 is tied to + 5V, then the registers on the 6551 are selected by any address of the form $9XX0 to $9XX3 where XX is a "don't care" number. Thus, in the pro- grams you will find the four 6551 registers selected by addresses $9400 to $9403. If you have a SYM-1 you can make use of device select DS18. If you have an Apple you must provide your own decoding cir- cuitry. The reason lies in the fact that the device select pulses generated by the Apple for the peripheral cards have been logically ANDED with 0„, and consequently they do not become active early enough in either the READ or WRITE cycles to work with 6500 family devices. For a discussion of address decoding see De Jong's '" book. The circuits are generally quite simple. In the case of the Apple, I suggest trying an inverter and a 74133 to generate a device pul.se for say $C08X, and perhaps a 74LS245 as a data bus buffer. Try an inverted 0, to replace 02, My familiarity with the PET does not justify sug- gesting any circuits, but I am sure the 6551 can be interfaced to a PET.
We turn next to the signals on the right-hand side of the 6551 as it is shown in Figure 1. The RXC input to the 6551 is the easiest to explain because it is not used in this application. The remaining pins have labels that are almost identical to the RS-232C designations. In fact, the only one that is different is the DCD which is simply CD (Carrier Detect) in RS-232C lingo, Again, refer to references (2) and (3) for a more complete explanation of the RS-232C in- terface.
Although the signal designations on the 6551 ACIA are almost identical to the RS-232C labels, the signal levels are not, and some arrangement must be made to transform the TTL levels of the 6551 to the RS-232C signal levels. We chose to use integrated circuits designed expressly for that task, namely the 1488 and the 1489 line driver and line receiver. Note that the 1488 requires a positive and negative supply voltage as well as ground. Also, the RS-232C ground (pin 7 on the DB-225 connector) should have the same ground as the 1488 and the 1489. The connec- tions in Figure 1 that are found on the right-hand side of the figure made up a rather complete RS- 232C serial interface that may be used to interface to a variety of peripheral devices. Furthermore, the fact that the data format and Baud rate of the 6551 are under the programmer's control makes this an ex- tremely flexible RS-232C interface.
Since computer communication by telephone is
the subject of this article, a modem is required. There are a variety of modems with RS-232C inter- faces on the market and we do not wish to make any recommendations about them. I purchased a Nova- tion Cat because that appears to be one of the more popular devices. Skyles Electric Works and other advertisers in COMPUTE[ offer modems for sale. In any case, my Novation Cat requires the signals designated in Figure 1 in addition to the signal ground. Other modems may require the DTR and RTS signals so we have shown the correct TTL-to- RS-232C interface in the event you may need these signals.
This completes our description of the circuit and we turn next to a simple program that is supposed to allow communication to take place using the 6551 ACIA.
Ill, A Simple Communications Program
A program that was designed to allow two people to communicate over telephone lines with their com- puters is given in Listing 1 and a flowchart is shown in Figure 2. This program is very simple and very slow, and it is offered here merely as a way to test the circuit, the program, and the modem. Eventual- ly, one would want to construct more elaborate routines to transfer information quickly. Our interest here is in experimenting for the sake of learning. Hence there is no necessity for encryption devices, bells, whistles or even parity checks.
Here is how it is supposed to work. The caller loads the program and places his modem in the originate mode with fuU-dupiex operation selected. He loads the indirect jump location with the vector $0F13 so that after the program is begun, his program will go to the transmit loop.
He makes the telephone call to an anxiously awaiting friend who also has this interface and this program operating. The friend has loaded the in- direct jump location at $0000 and $0001 with the vector S0F26 (remember, $26 goes in $0000 and $0F goes in $0001). The I'ricnd has also jilaced his modem in the answer mode with full-duplex opera- tion selected. After an informal chat, both friends put their modems into action by placing the handset into the muffs (assuming acoustic modems). The originator begins to type a message.
He ends his part of the message with an 'EOT' character (Control D on your keyboard). While he is transmitting, the friend's program echoes the message back to the originator where it is read and printed by the computer. It's nice to see what you have said, and to know that it got where it was going with no mistakes. When an 'EOT' character is sent, it automatically transfers the originator's program to the receive loop and the receiver's program to the send loop, giving him a chance to retaliate. Having made no visible symbol to indicate when this changeover takes place, may I suggest sending a
Morch. 1981 Issue lO.
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32
COMPUTE!
March, 1961 Issue 10.
Listing 1. An Experimental Conimunications Routine.
$0F00 A9 OB START
0F02 8D 02 94 0F05 A9 13
0F07 8D 03 94
OFOA 78 OFOB D8 OFOC EA OFOD AD 01 94 OFIO 6C 00 00
0F13 20 3C E9 TXLOOP
0F16 20 FO OF
0F19 C9 04
OFIB FO 09
OFID 20 EO OF
0F2O 20 7A E9
0F23 18
0F24 90 ED
0F26 20 EO OF RXLOOP
0F29 C9 04
0F2B FO E6 0F2D 20 FO OF 0F30 20 7A E9
0F33 18 0F34 90 FO
Subroutines
LDA #S13
STA CNTRG
SEI
CLD
NOP
LDA STATUS
JSR KYBD JSR TXMIT CMP #"EOT'
JSR RCVDAT JSR OUTPUT CLC
|
OFEO AD 01 94 |
RCVDAT |
LDA STATUS |
|
0FE3 29 08 |
AND n08 |
|
|
0FE5 FO F9 |
BEQ RCVDAT |
|
|
0FE7 AD 00 94 |
LDA RCVRG |
|
|
OFEA 60 |
RTS |
|
|
OFFO 48 |
TXMIT |
PHA |
|
OFFl AD 01 94 |
WAIT |
LDA STATUS |
|
0FF4 29 10 |
AND #$10 |
|
|
0FF6 FO F9 |
BEQ WAIT |
|
|
0FF8 68 |
PLA |
|
|
0FF9 8D 00 94 |
STA TMTRG |
|
|
OFFC 60 |
RTS |
LDA #SOB Initialize the 6551 by loading the
command STA CMNDRG register (see 6551 spec sheet for
details).
Load the control register for 8-bit
word
length and Baud rate of 110.
Prevent interrupts.
Clear decimal mode.
A mistake of mine.
Clear any interrupts on the 65.') 1. JMP (THERE) Jump to transmit loop to transmit,
receive
loop to receive. Get a character
from the
keyboard read routine. Send it to
the 6551
transmit subroutine. If an "End of
Transmission" BEQ RXLOOP (Control D) is sent, branch to
receive loop.
Get the echo from the receive
subroutine.
Output it to your own printer to see
what you
sent. Force a jump back to
TXLOOP BCC TXLOOP and get another character to send. JSR RCVDAT Wait for a character to be sent. CMP #'EOT' Is he finished with his transmis- sion? BEQ TXLOOP Yes, then go to transmit loop. JSR TXMIT Echo the character that was sent, JSR OUTPUT Output the character to your
printer. CLC Force a jump back to RXLOOP
BCC RXLOOP and get another character when it is
sent.
Read the status register to sec if a
word
has been received, otherwise wait
for one.
Get the word from the receiver
register.
Return to the calling program.
Save the accumulator temporarily
Is the transmitter register empty?
No. Wait until it is.
Get the character from the stack.
Store it in the 6551 transmit
register.
Return to the calling program.
IN[TIAUZ£ THE
MSI
IMllSKCI
JUMP TO
\ A LOOP
CltrCKARACTF-B KEOM Kr.V- n{lARI>SOb HfJtTINF.
Tlt*>5MIT IT
KITHTBANSMn
SVPRULT^INi
GET ' T.CHt) ' mOM RECEIVL Sl'ShOLTINF
PRINT IT WITH OtTPLT SLBHOLTI.NE
>
[;et(:haka( uh
Wtrjl UK. KIM
MBiifit riM
ICHO IT MITM TIL*>'SVnT SLTlBlJTn.NE
Figure 2. Flowchart of the Transmit/Receive Program. Sec text for details.
question mark, or perhaps there is some CB lingo that suggests it is the other person's turn to tallt. If all else fails, pick up the handset and holler something. Do not change your modem from its original answer or originate mode.
So back and forth the conversation goes. Once you have the transmit option in your hands nothing can stop you from talking until you send an 'EOT' and give your friend a chance to say something. Clearly, the program lacks a certain elegance (it may
not even work, in which case it lacks a whole lot of elegance), but maybe it will get some fun started. By the way, the originator of the phone call usually gets the phone bill.
Study the flowchart and the program listing. The program begins by intitializing the 6551. An eight-bit word (TTY compatible) is used, with the parity check disabled, and one stop bit is sent. The Baud rate chosen here is 110, but it should be possi- ble to go to 300 Baud. Both participants must have
March. 1981. Issue lO.
COMPUTE!
33
the same rate. Next, the program jumps to either the receive loop or the transmit loop depending on the vector loaded into $0000 and $0001. This was a crude way to start, but it should work.
In the transmit loop the program first waits for an input from a keyboard read routine. The address in the program belongs to an AIM 65 monitor subroutine that returns the ASCII representation of the depressed key in the accumulator. This character is sent by calling the transmit subroutine which loads the 6551 transmit register with the character. The 6551 takes over and sends the character. The pro- gram then waits for the character to be echoed from the other telephone and computer. The echoed character is printed to make sure that what was sent was actually received. Then control returns to the keyboard subroutine to wait for the next character to be sent.
In the receive loop the program jumps to the receive subroutine that watches the 6551 until a character is in the receive data register. If this character is an 'EOT' then control goes back to the transmit loop and you may begin transmitting. Otherwise the received character is immediately echoed back to the sender and also printed with your OUTPUT routine. Again, the address of the OUT- PUT routine in Listing 1 belongs to an AIM 65 subroutine. Both the KYBD and OUTPUT subroutines must be supplied by the user's monitor or the user himself, otherwise the program in Listing 1 is complete.
While in the transmit loop, the selection of the 'EOT' character by the sender will automatically transfer control out of the transmit loop into the receive loop. Note again that no bells or whistles have been programmed to occur when you send an 'EOT' character, so if you are transmitting you bet- ter let your friend know you are passing control of the system to him.
So hopefully all this will work. If it doesn't you have only me to blame, and I will not assume the cost of your labor or your equipment to conduct this experiment. Perhaps it would be best if you waited until someone else tried it; think it over before you take the plunge.
Besides, my next project is to launch a 6502 Communications Satellite using dynamite in my back yard and you may want to save your money to buy shares in that enterprise.
References
1. De Jong, Marvin L., Programming & Interfacing the 6502, With Experiments, Howard W. Sams & Co., Inc. Indianapolis, 1980.
2. Day, Michael E., "RS232 Communications,", COMPUTE!, Sept/Oct 1980, 26.
3. Ciarcia, Steve, "I/O Expansion for the TRS-80," BYTE, June 1980, 42. ©
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• Objective reviews and comparisons of software available for your computer
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Microcomputer Measurement And Control For PET,APPLE,KIM and AIM65
The world wc live in is full of variables we want to measure. These include weighi. temperature, pressure, humidity, speed and fluid level. These variables are continuous and their values may be represented by a voltage. This \oltage is the analog of the physical variable. A device which converts a physical, mechanical or chemical quantity lo a voltage is called a sensor.
Computers do not understaiid voltages: They understand bits. Bits are digital signals. A device which converts voltages to bits is an analog-to-digital converter. Our AIM 16 (Analog Input Module) is a 16 input analog-to-digital converter.
The goal of Connecticut microcomputer in designing the uMAC SYSTEMS is to produce easy lo use, low cost data acquisition and control modules for small computers. These acquisition and control modules will include digital input sensing (e.g. switches), analog input sensing (e.g. temperature, humidity), digital output control (e.g. lamps, motors, alarms), and analog output control (e.g. X-Y plotters, or oscilloscopes).
Connectors
The AIM 16 requires connections to its input port (analog inputs) and its output port (computer inter- face). The ICON (Input CONnector) is a 20 pin, soWer eyelet, edge connector for connecting inputs to each of the AlM16's 16 channels. The OCON (Output CONnector) is a 20 pin, solder eyelet edge connector for connecting the computer's input and output ports to the A1M16,
The MANMODl (MANifold MODule) replaces the ICON. It has screw terminals and barrier strips for ail 16 inputs for connecting pots, joysticks, voltage sources, etc.
CABLE A24 (24 inch interconnect cable) has an interface connector on one end and an OCON equivalent on the other. This cable provides connec- tions between the uMACSYSTEMS computer inter- faces and the AIM 16 or XPANDRl and between the XPANDRl and up lo eight AIM 16s.
Analog Input Module .
The AIM 16 is a 16 channel analog to digital converter designed lo work with most microcornputers. The AIM 16 is connected to the host computer through the computer's 8 bit input port and 8 bit output port, or through one of the uMAC SYSTEMS special inter- faces.
The input voltage range is 0 to 5,12 volts. The in- put vohage is convened to a count between 0 and 255 (tX) and FF hex). Resolution is 20 millivolts per count. .Accuracy is O.S'To ± 1 bit. Conversion time is less than 100 microseconds per channel. All 16 channels can be scanned in less than 1.5 milliseconds.
Power requirements arc 12 volts DC at 60 ma.
POWl
The POWl is the power module for the AIM16. One POVS'l supplies enough power for one A1M16, one .MANMODl, sixteen sensors, one XPANDRl and one computer interface. The POWl comes in an American version (POWl a) for 110 VAC and in a European ver- sion (POWl e) for 230 VAC.
"^"^ TEMPSENS ^.f,
This module provides two temperature probes for use by the AIM16. This module should be used with the MANMODl for ease of hookup. The MANMODl will support up to 16 probes (eight TEMPSENS inodulcs). Resolution for each probe is TF.
Remote Controller- Clock and Calendar
AN INEXPENSIVE CONTROL SOLUTION FOR HOME SECURITY • ENERGY CON- SERVATION • GREENHOUSES
• ENVIRONMENTAL CONTROL
• INDUSTRIAL CONTROL
• LABORATORIES
SUPER X-10 MOD SPECS
1. Remote controller
Controls up to 256 different remote devices by sen- ding signals over the house wiring to remote modules. Uses BSR remote modules available all over the USA (Sears, Radio Shack, etc.). Does not require BSR control module. Docs not use sonic link.
2. Clock/calendar
Time of day - hours, minutes, seconds
Date - month, day - automatically corrects for
28,29,30 and 31 day months. Day of (he week.
3. Digital input/outputs
8 inputs - TTL levels or switch closures.
Can be used as a trigger for a stored
sequence. 8 outputs - TTL levels
Power supply included llOVAC only.
XPANDRl
The XPANDRl allows up to eiglit Input/Output modules to be connected to a computer at one time. The XPANDRl is connected to the computer in place of the A1M16 or XIO MOD, Up to eight AIM16s or seven Aim 16s and one XIO MOD are then connected to each of the eight pons provided using a CABLE A24 f^or each module.
For your convenience the A1,M16 and the XIO MOD come as part of a number ol sets The minimum confiauraiion for a usable system is the AIM16 Starter Set 1 which includes one AIM16, one POWl, one ICON and one OCON. The A1M16 Starter Set 2 includes a MANMODl in place of the ICON, The minimum configura- tion for a usable system is the XIO MOD Starter Set which includes one XIO MOD,
one ICON arid one OCON. These sets require that you have a hardware knowledge of your computer and of computer interfacing.
For simple plug compatible systems we also offer computer interfaces and sets for many computers.
A1M16 ns-oo
SUPER XIO MOD (1 !0 VAC only) 249.00
POWla (POWer module- 1 10 VAC) 14.9S
POWIe (POWcr module-230 VAC) 24,95
ICON (Input CONnector) 9.95
OCON (Output CONnector) 9.95
MANMODl (MANifold MODule) 59,95
CABLE A24 (24 inch interconnect
cable) "-^
XPANDRl (allows up to 8 Input or Output modules to be connected to a
computer at one time) 59.95
TEMPSENS2P1 (two temperature probes,
-10"F to 160°I0 '•'•"S
LIGHTSENSIPI (light level probe) 89.95
The following sets include one .■MMie, one POWl, one OCON and one ICON.
A1,M16 Starter Set la {1 10 VAC) 189.00
AIM16 Starter Set le (230 VAC) 199-00
All prices and specifications subject 10 change without notice. Our JO-day m&ncy back guarantee applies.
The following sets include one A1MI6,
one POWl, one OCON and one MANMODL
AIM16 Starter Set 2a (1 10 VAC) 239.00
AIM16 Starter Set 2e (230 VAC) 249.00
The following modules plug into their respective computers and, when used with a CABLE A24, eliminate the need for custom wiring of the coinputer interface,
PETMOD (Commodore PET) 49.95
KIMMOD (K1M,SYM) 39.95
APMOD (APPLE II) 59.95
TRS-80 MOD (Radio Shack TRS-80) 59.95
A1M65 MOD (AIM 65) 39.95
The following sets include one AIM 16, one POWl, one MANMODl, one CABLE A24 and one computer inter- face module PETSETIa (Commodore PET -
llOVAC) 295,00
PETSETle (Commodore PET •
230 VAC) 305,00
KlMSETla (K1M,SVM,AIM65 -
1 10 VAC) 285.00
KlMSETle (K1M,SVM,AIM65 -
230 VAC) 295.00
APSETla(APPLE 11-110 VAC) 295.00
APSETIe(APPLE 11-230 VAC) 305.00
TRS-80 SETla (Radio Shack TRS-80 -
1 10 VAC) 295.00
TRS-80 SETle(Radio Shack TRS-80 -
230 VAC) 305.00
AIM65 SETla(AlM65-l 10 VAC) 285.00
A1M65 SETle(AIM65-230 VAC) 295.00
The following sets include one XIO MOD, one CABLE A24. one ICON and one computer interface module.
PETSET2(Commodore PET) 295.00
K1MSET2(KIM,SVM) .285.00
APSET2(APPLE II) 295.00
TRS-80 SET2 (Radio Shack TRS-80) 295.00
AiM65 SET2 (A1M65) 285.00
SUPER XIO MOD/XPANDRI SET2 (if you already havca SETl) 295.00
Printer And Communication Interfaces For The CBM/PET
SADI Fo"- Serial
Two-way
Communication,
Parallel
Printers,
and Serial
Printers
ADA1600 • For Parallel NEC and Centronics Standard Printers
SADI - The microprocessor based serial and parallel interface for the Commodore PET. SADI allows you to connect your PET lo parallel and serial printers, CRT's, modems, acoustic couplers, hard copy ter- minals and other computers. The serial and parallel ports are indepen- deni allowing the PET lo commutiicate with both peripheral devices simultaneously or one at a time. In addition, the RS-232 device can communicate with the parallel device. Special Features for the PET interface include:
Conversion to true ASCII both in and out
Cursor controls and function characters specially printed
Selectable reversal of upper and lower case
Addressable - works with other devices Special Features for the serial interface include:
Baud rate selectable from 75 to 96CX)
Half or full duplex
32 character buffer
X-ON, X-OFF automatically sent
Selectable carriage return delay Special Features for the parallel interface include;
Data strobe - either polarity
Device ready - either polarity
Centronics compatible Complete with power supply, PET IEEE cable, RS-232 connector, parallel port connector and case. Assembled and tested.
SADIa(IIOVAC)S295
SADIc {230V AC) S325
The ADAI600 is a low cost easy to use ititerface for the Commodore Cornpiilcrs. II allows the PET and CUM computers lo use standard Centronics type prinlers (in- ciuding the NEC 5530) for improved quality priming. The ADA1600 has a Iwo fool cable which plug.5 into the PET IEEE port. Another IEEE card edge connector is provided for connecting disk.s and other peripherals lo the PET. The ADAI600 is addressable and does not tie up the bus. The address is switch selectable. A four foot cable with a standard 36 pin Centronics connector is provided. A switch sclect.s upper/lower case, upper/lower case reversed (needed for some Commodore machines) and upper case only for clearer program listings. Works with WORDPRO, BASIC and other software. No special programming is required. The case measures 3 1/2 x 5 3/4 inches. Comes complete, as.sembled and tested, with case and cables. Power is obtained from the printer or an e.Mcrnal power supply may be used. Retail price forthc ADAI600isSI29. i .-. .> j i
ADA1450 • Serial Printer Adapters
The ADAH50 is a low cost, easy to use serial interface for the Commodore Computers. It allows the PET and CBM computers to use standard serial printers for im- proved qualhy printing. The ADA1450 has a two foot cable which plugs into the PET IEEE port. .Another IEEE card edge connector is provided for connecting disks and other peripherals to the PET. The ADA1450 is addressable and docs not tic up the bus. The address is switch selectable, A sis foot RS-232 cable is provided with a DB25 connector. Pin 3 is data out. Pins 5,6 and 8 act as ready lines lo the printer, Pins 4 and 20 act as ready lines from Ihc printer. These lines can be switched for non-standard printers. Baud rate is selectable to 9600 baud, ,A switch selects upper/lower case, upper/lower case reversed (needed for some Commodore machines) and upper case only for clearer program listings. Works with WORDPRO, BASIC and other .software. No special programming is required. The case measures 3 1/2 x 5 3/4 inches. Comes complete, assembled and tested, with case, cables, power supply and soft> are on cassette for graphing functions, formatting data etc. The ADAI450 has a female DB25 connector at the end of the RS-232 cable for most standard printers. The ADA1450N has a male DB25 at the end of the RS-232 cable for the DIABLO serial printers. Retail price for the ADA1450 or I450N is SI 39.
ADA730 Parallel • For the Centronics 730 and 737 Printers
The ADA730 i.5 a low com easy to use interlace for the Commodore Computers. It allows Ihc PET and CBM computers lo use Centronics type 730 and 737 prinlers. The ADA730 has a two fool cable which plugs into ihe PET IEEE port. Another IEEE card edge connector is provided lor connecting disks and other peripherals to the PET. The ADA730 is addressable and doe.s not lie up the bus. The address is switch selectable. A cable with a 36 pin card edge connector is provided. A swiich .selects upper/lower coase, upper/lower case reversed (needed for some Commodore machines) and upper case only for clearer program listings. Works with WORD- PRO, BASIC and other software. No special programming is required. The case measures 3 i/2 \ 5 3/4 inches. Conies complete, assembled and tested, with case and cables. Power is obtained from the printer or an external power supply may be used. Retail price for the ADA is S129,
%M
Word Processor Program •
PET Word Processor. On tape -
S39.50. On disk - 49.50
For 8K Pets 29.50
For 16K and 32K Pets 39.50
Compose and print letters, llycrs,
ads, manuscripts, etc. Uses disk o
tape. 30 page manual included.
ADA400 RS-232 To Current Loop Adapter
RS-232 to current loop adapter (ADA 400).
S29.50
Two circuits - 1 each direction. Run an RS'232
device off a computer's teletype port or vice
versa. Optoisolated.
ADA4005 - Solder Pads 24.50 ADA400B - Barrier Strips with screw terminals 29.50
In the US order from: Connecticut Microcomputer, Inc. 34 Del Mar Drive Brook field, CT 06804 (203) 775-4595 In Canada order from: Batlerie.^ Included, LTD 71 McCaul St. F6 Toronto, Canada M5T2X1 (416)596-1405
QUANTITY DESCRIPTION PRICE TOTAL
SUBTOTAL
Handling and shipping — add per order
S3.00
Foreign orders add lOVc for AIR postage Conn, residents add 7% sales tax
TOTAL ENCLOSED
NAME
COMPANY ADDRESS
CITY _
STATE .
VISA O M/C O Expiration date. Card number
.ZIP.
Mention this magazine and deduct 2% from the TOTAL
Connecticut microcomputer, Inc.
34 Del Mar Drive, BrookfieW, CT 06804 203 775-4595 TWX: 710 456-0052
36
COMPUTE!
March, 1961. Issue lO,
Basics
of Light Pen
Operation
Robert A. Peck
Manager, Technical Support to Advonced Manufacturing Mennorex Corporation
Manufacturers of personal computers are attempting to make the computer more easily accessible to the public. In doing so, various means have been tried, such as games, simple home budget programs, and the like. The entry format for each of these had, for the most part, been by means of the keyboard, or a game paddle of some kind.
Just recently, the trend toward light pen "menu" selection for ease of data entry has been tried. Let's look at the actual techniques which could be employed to implement this type of input device on a personal computer. The hardware and software requirements will be discussed here. The reader, after studying these techniques, may be able to con- struct a working form of a light pen with as little as $5.00 worth of materials.
First a note about the definition of a light pen. It does not emit light . . . rather it is intended to sense the light of an illuminated area on the TV monitor screen. As a photo-sensitive device, some form of output of the light pen will occur as a result of the electron beam energizing a portion of the phosphor of the screen, thus causing it to glow.
To clarify this a bit further, the picture on a TV screen is not all produced at exactly the same time by a single "photo" flashed on the screen. Instead it is made up of a single electron beam being swept from left to right (and down and up) across the screen, with its intensity varied as it sweeps across the screen, to form the picture we see, one line at a time. In this manner, the sweeping beam produces 30 or 60 complete pictures per second on the TV screen. Our own visual system enables us to perceive the screen as though the entire surface of the screen was continuously lit, thus forming a complete pic- ture. The persistence of the screen, the time it re- mains bright after the beam has passed a particular location, is minimal for most monitor screens.
Let's act, for the moment, in the same manner that the light pen will act. Imagine, if you will, tak-
ing a small cylindrical tube and placing it against the surface of a fully illuminated TV screen. If we place our eyes at the opposite end of this tube, and restrict our vision only to what is at the end of the tube and not to the rest of the screen, we are in a position to make a judgement about what is going on in our narrowly restricted view of the world.
Now we must imagine either that we are able to speed up our ability to perceive rapidly the changing intensity of the light on the area of the screen in front of us or that the beam slows down to our level of perception. Either position is ok for our purposes.
As we are looking into the end of the tube, we will notice that there is no light there most of the time. Specifically the phosphor will only be lit up ex- actly at the time the beam is striking it, and for a short time thereafter, based on the persistence of the screen. But of course, for the most part, we will be kept in the dark. This will be true at any position on the surface of the screen.
Since we know that we have light for a short time and dark for the rest of the time, it is a yes-no situation and something ideally suited to being handled by the computer. So let's give our eyes a rest and place a lens and a phototransistor within the tube in place of our eye. We know that the phototransistor will produce an output when it sees the light and no output when the light is absent.
...a very simple design will serve most purposes admirably.
How complex must the circuit for the phototran- sistor be to allow us to make this a useful, reliable device? Well, it depends on the type of selection which we wish to make in the usage of the light pen. We'll soon see that for the largest percentage of potential uses, at least at the hobbyist level, a very simple design will serve most purposes admirably.
In order to grasp the significance of the out- put/no output capability of the phototransistor, we'll next look at the way the computer or its terminal device is producing the output display which we are seeing on the TV.
Let's say we have a terminal which can display 80 columns by 24 tines of usable character positions on the monitor screen. In the process of output, the scan controller must select, each in turn, line 1 of the character memory, then columns 1 , 2, 3, . . . , all the way out to column 80, Then it must repeat the line scan for as many TV scan lines a character line is supposed to take up. Then it will go on to the next line of 80 characters, the next, and so forth, going back to the beginning again once all 25 lines have been displayed.
SVte&ggjr;
GRAPHICS
FOR 80 COLUMN PETS
The Integrated Visible Memory for the PET has now been redesigned for the new 12" screen 80 column and forthcoming 40 column PET computers from Com- modore. Like earlier MTU units, the new K-1 008-43 package mounts inside the PET case for total protection. To make the power and flexibility of the 320 by 200 bit mapped pixel graphics display easily accessible, we have de- i signed the Keyword Graphic Program. This adds 45 graphics commands to . Commodore BASIC. The image ' on the screen was created by the program below. If you have been^ waiting for easy to use, high -^^ resolution graphics for your PET, isn't it time you called MTU?
mfMm);:mmm^
■>r!-';«''-;.VvV.
'•m:
'm
ra^B^^K^BB^
NOW 80 COLUMN PETS CAN HAVE MTU HIGH RESOLUTION GRAPHICS
10 VISMEM: CLEAR
20 P=160: Q=100
30 XP=144: XR=1. 5*3. 1415927
40 YP=56: YR=1: ZP=64
50 XF=XR/XP: YF=YP/YR: ZF=XR/ZP
60 FOR ZI=-Q TO Q-1
70 IF ZK-ZP OR ZI>ZP GOTO 150
80 ZT=ZI*XP/ZP: ZZ=ZI
90 XL=INT( .5+SQR(XP*XP-ZT*ZT) )
100 FOR XI=-XL TO XL
110 XT=SQR{XI*XI+ZT*ZT)*XF: XX=XI|
120 YY= (SIN(XT)+.4*SIN{3*XT) ) *YF
130 GOSUB 170
140 NEXT XI
150 NEXT ZI
160 STOP
170 X1=XX+ZZ+P
180 Y1=YY-ZZ+Q
190 GMODE 1: MOVE XI, Yl: WRPIX
200 IF Y1=0 GOTO 220
210 GMODE 2: LINE Xl,Yl-l,Xl,0
2 20 RETURN
m
Hi
pi
MySss,K.-
'"rSjh-^:3;
'■ ; M^^ ^'^^mM:i-
Vii>!
K-1008-43M Manual only $10
(credited toward purchase)
K-1 008-43 Complete ready to install package $495
-.h^.'
§MMiM)iM^iMMMMi
MASTERCHARGE & VISA accepted
Write or call today for our full line catalog describing all MTU 6502 products, including our high speed 8" Floppy Disk Controller for up to 4 megabytes of PET storage. -^.z.,^ ■ »«„i»;.„
.^Micro Technology Unlimited
r 2806 Hillsborough Street , P.O. Box 12106 Raleigh. NC 27605. U.S.A. 19191833-1458 .. ■
^mm^^m^
^m-^
38
COMPUTEl
Morch, 1981, Issue lO.
From this, you can see that the scan controller will be continuously fetching characters from the character memory. Thus the different addresses of the different characters will each be available on the address bus of the scan controller at the time that character is being fetched for output.
To put it another way, if our character memory was set up such that line 1 position 1 represented ad- dress 0 of the character memory and line 1 position 80 represented character address 79, line 2 position 1 as address 80 and line 25 position 80 as address 1999, we would then have a specific point of reference to use. We now take our light pen and place it on the screen directly over one specific character position which is, let us say, occupied by a single solid block character such as a nonblinking cursor.
Every time the phototransistor sees a light out- put on the screen, at the exact time it occurs, the scan controller address bus has, on it, the exact ad- dress within the scan memory occupied by the character which is producing the light output on the screen.
Just as an example of what this address would mean to us, consider the following example. Suppose that at screen location 400 (first position in line 6) we place a cursor character followed by the description .. "CHECKBOOK BALANCER" and at location 800 in the scan memory we placed another cursor character labeled "TREK", we can place the light pen over the cursor character representing the specific program which we wish to have called in next and will expect the light pen scan program to provide us with the data required to do it. In this case when the light pen senses an output, the address of either position 400 or 800 will be on the scan posi- tion address bus, ready to be picked up for use by our program. We know that if our program finds 400 on the bus, it must next call in the Checkbook Pro- gram. Conversely, if it finds 800 on the bus, it must retrieve the Startrek Program.
Now if we wanted to do so, we would add some additional hardware to our terminal which would act, in association with the phototransistor output, to cap- ture the address present on the bus at the time a light output is sensed. As an exercise, let's examine some of the hardware this would require.
First we need something to capture the scan ad- dress from the controller bus and a way to transfer it to the data bus of the computer. A set of three 74175's could be used here. Each is a 4-bit tri-state latch, where the input (capture side) would be con- nected to the scan memory data bus and the output (storage side) would be connected to the computer data bus for later retrieval. The control lines for the latches would have to be connected in some manner to the light pen through a flip-flop of some kind to assure only a single sampling of the address from the scan counter per application of the light pen to the
The best features of this technique
are the simpiicity of the
software required and the
non-critical nature of the
components of the light pen...
screen. The tri-state control lines would be connected to the address decoders of the computer so that it could retrieve any one of the three 4-bit stored parts of the scan address after it was triggered.
It might, at first glance, seem a pretty straightforward approach to follow, but let's look at a few of the drawbacks. The first would be the critical control of the level of light intensity sensed by the pen. Specifically, it could possibly be accidentally triggered either by an outside .source of light, or by the phosphor pcrsistancc (as little as there is) when we first place the pen against the surface of the screen. In either case, the address we sense on the scan control bus does not really represent the actual address of the sample point we are trying to isolate. This might entail some special circuitry to be added to sense only the rising edge of the beam light inten- sity, where that rising edge has a specific rise time, and therefore not trigger on an outside incandescent light source operating on a 60 Hz sine wave.
To complicate matters further, even though we succeeded in developing this type of edge sensitive equipment, we still run into some problems with fluorescent light sources in the area, in that these have a very fast rise time and have a phosphor afterglow as well. Both items make the light from the fluorescent vary in a manner similar to that of the TV screen. Our software could, of course, compen- sate for this, but combined with the hardware re- quirements, we have selected a really complex task. One more area of difficulty, just to mention it here, is the inability to accurately sense the difference in address locations between two adjacent, or very near- ly adjacent, squares on the screen unless special cir- cuitry is added for the rise-edge, as described above.
Fortunately, there is a way to absolutely minimize the amount of circuitry needed to establish a workable light pen, along with a way to minimize the complexity of the software which has to go along with it. In addition, the pen needs only to accept a source of power and ground from the computer, and will need only a single bit input port to operate fully. Some manufacturers suggest the use of the same pad- dle input for the light pen. Below is described the technique which can accomplish this form of opera- tion.
The best features of this technique are the simplicity of the software required and the non- critical nature of the components of the light pen, as
March. 1981. Issue lO.
COMPUTE!
39
SORT is u 6502 machine liinguage in-memory sorting algorithm of commercial quality for PET ;incl APPLE owners. Most sorts are acconiplishetl in less than a second and large sorts take only a few seconds. The algorithm is a diminishing increment insertion sort, with optionally chosen increments. There are no conditions under which SORT performance degenerates or fails.
SORT requires almost no user set-up operations. SORT handles integer, floating-point, and string arrays plus arrays of more than one dimension. In ;iddition, multi key sorting of string arrays has lieen enahled. The user may specify the character within a string to hegiii sorting on and how many characters are to he evaluated. SORT is capable of performing up to twenty of these multi-kev suh-sorts (on matches found) at the same time.
SORT on the PET: SORT is available for large-keyhoard PETS onlv. One EPROM fits all newer 40 B 80 column PETS. SORT EI^ROM comes at hex $9000, SAOOO, or SBOOO socket. EPROM with SORT and text dump is $55.00 (postpaid).
SORT on the APPLE II via a quality slot independent EPROM board. Board includes function driver that supports 16 EPROM based functions for user EPROMS. APPLE EPROM card with SORT, text screen dump and function driver is $110.00 (postpaid). MASTERCHARGE y VISA accepted.
by MATRIX in EPROM for the PET and APPLE II,
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. MEMOHV BOARD EDGE CONNECTOR PLUGS INTO THE 6aOCS44 BUS
« CONNECTS TO PET OR KIM USING AN ADAPTOR CABLE
* REllABLE-DVNAMJC RAM WITH ON BOARD INVISIBLE REFRESH-LOOKS LIKE STATIC MEMORY BUT AT LOWEfl COST AND A FRACTION OF THE POWER REQUIRED FOn STATIC BOARDS
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40
COMPUTE!
March, 1981. Issue lO,
well as the non-critical nature of the level ad- justments required. We also have an easy way of compensating for any external light source which may have an effect on the pen, and actually ignore it. Let's examine this technique now.
First, let us attack the problem of light sensiti- vity adjustment. It is proposed that, for this method we will work with, the pen need only be able to distinguish between the presence or absence of il- lumination within a selected square on the screen. If we are working within a range of light or no light, you can see that we will have a wide degree of ad- justment available and still allow the pen to operate perfectly well.
With the original example, let's say we had placed a menu selection box at both scan memory locations 400 and 800 and assume also we are using the simple-form light pen which plugs into the game paddle input. Instead of using a hardware-based scan technique, we will use a software based scan as follows.
Assume for example that we have placed the pen over the square at scan location 800 and we begin our scan. Both the square at 400 and at 800 appear illuminated at this time. Therefore if the light pen is pointing to either one of them, during the period of time of the sweep of the beam across the screen, the light pen will put out a series of pulses coincident with the presence of the beam in the area occupied by the pen.
Now we can begin our scan by replacing the selector box at scan memory location 400 with a blank space (no output on the screen at this point). We will then go to the light pen input and stay in a loop for about 1/60 or 1/30 second and find out if, during that loop, there were any light pulses output. If there were still output light pulses, it means that we had not turned off the square over which the light pen is resting now, so we must continue the scan. Then we relight the square at location 400 and pro- ceed to replace the square at 800 with a blank space. We will again loop through the test program area to determine if there have been any light pulse outputs during the time that location 800 was turned off. If no outputs were sensed during this time, we know we have found the correct location where the light pen is sitting.
We can then take the address we have found this way and use it to control which action is to be done next, just as in the previous hardware con- trolled case, but here with a good deal less com- plexity. You can also see that we may have many many menu boxes on the screen and by this means accurately determine exactly which one is being ad- dressed by the light pen. After all, we are the one who is controlling whether the light pen can see a Hght output from a specific square. So if we turn off a square, and then see that the light pen no longer has an output, we know which square we just con-
trolled and therfore we know what the required operation will be.
We have then substituted a software scan tech- nique for both the complex hardware and complex software the other approach would have required. The primary limit in the number of menu boxes we can use is the amount of time which would be re- quired, at 1/60 or 1/30 sec per box, for the light- pulse-present scan per box on screen. If we have no concern for the time this takes, then there is little reason to limit the number of boxes on the screen ex- cept to keep them far enough apart so that the light pen will see the light output from only one at a time, maintaining the wide range of light sensitivity we dis- cussed earlier.
...thus far we have substituted
a software scan for the set
of complex hardware.
Speaking of light sensitivity, let's discuss the way we'd handle an outside light source and ignore its influence in our selection of the item to be per- formed. First, a reminder that the single spot on the TV screen we are monitoring is dark for most of the time and is lit by sweeps of the beam only as it passes the area we are monitoring. Now if we con- sider the outside source of light, it will ralher seen to be a continuous sequence of pulses (fluorescent) or a continuous single light level. In the event that there is some continuous pulse interference, we must ad- just our software to test that there are no more than X (let's say 50) pulses which occur during a single sweep through our software scan subroutine. This would allow us to ignore such interference as is caused by either a fluorescent or an incandescent source. Certain types of light, such as the sun, can- not be distinguished by the pen as a wave, so are translated as a continuous level, thereby resulting in nearly zero (perhaps one) transitions during the time of a single scan. Thus, we decide that unless greater than one and less than 50 pen state transitions have occurred in one scan, we could probably assume that the visible part of the screen scan probably had been triggered by an outside source, and we can enter into some type of wait state, scanning the pen it.self for a time when the correct number of transitions is sensed and, within the wait state loop, also scan our keyboard and any other alternate input device which may be connected to the system and intended for use with the particular program as an input.
A final note about outside light sources; when we have the pen up against the screen, the major in- fluence on the pen will be the light from the screen alone. In this position, the pen will not be affected very much by the outside light.
Morch, 1981. Issue lO.
COMPUTEI
41
So thus far we have substituted a software scan for the set of complex hardware. We have used a technique which requires very httle translation of ad- dress sensed into work to be done. We could pro- bably go into the type of construction required for the light pen itself.
But wait, there seems to be some griping from the back of the room. Yes . . . Oh , . . OK! The gentleman in the last row says "That's ok for you guys who have the Visible Memory (direct access) display screens, but how about the rest of us who on- ly have the scrolling type of screen?"
A fair question, I agree. All right. A scrolling type of screen is one where everything moves up one notch to make room for the bottom line once the screen is filled. Well, a number of these types of screens have the ability to move the cursor in a relative manner or an absolute manner. If it does have this capability, then the technique still works exactly the same way. ..we just have to work a little harder. Lets look at a quick example.
We'll print a cursor box followed by a descrip- tive line on the screen, followed by a blank line, and repeat this for 5 selections. Now to do the cursor scan, we will begin from the lower left (home) cursor position and move-relative-cursor until we get to the position occupied by one of the selector boxes. Then we replace it with a blank space instead. Scan. Are there light pulses present? If not, we've found the
TRS-80 „ . , cr. OA -rn H^^lh H-8
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EPROM Programmer
PET ' APPLE » AIM-65 » KIM-1 • SYM-1 • OHIO SCIENTIFIC
Software avdilihlr for F 8, 6800. 8085, 8080, Z-80, 6502 1802 2650. 6809 basec! svsleiiis.
EPROM type is selected by a personality module which plugs into the front of the programmer. Power requirements are 115 VAC 50/60 Hz. at 15 watts. It is supplied with a 36 inch ribbon cable for connectinq to microcomputer Requires I'v 1/0 ports. Priced at Si 69.00 \.i.iili one set of softvrare. (Acldilional software on disk and cassette for various systems.) Personality modules are shown below.
Pan No. Programs Price
PMO ™S 27l« V17IH1
PM 1 27rW.27n8 171X1
PM2 2732 .13(MI
PM.) TMS 2716 17 nil
PM4 ™s 2,s:(2 :i:io(i
Pf^.S TMS 2.^1b.271h.27.'W 171)11
Pt^S MCMW7M :i?,(lli
Optimal Technology, Inc.
Blue Wood 127, Earlysville, Virginia 22936 Phone (804) 973-54S2
light pen position. If so, cursor backspace, put back the selector box, space relative cursor to the next selector box and repeat the process. As you can see, there is no basic change in the procedure, just a slightly different approach.
Sir, . . .you do have relative cursor?! Ok then, at least we've got one satisfied customer. By the way, you'd probably be interested; the terminal I use on ray machine is a scrolling type and thats why I was prepared for that question!
Now for the construction of the light pen itself. We'll need some kind of small cylinder to house it. The cylinder will have to have enough room for the phototransistor itself. And, it should have some room for a small variable resistor and a voltage comparator IC if we want to have it fully self-contained and ready to plug into the game paddle input of our computer.
I have provided a sketch of the proposed con- struction of the pen, along whh the schematic of the one I use. These parts I had were primarily junk-box components, and as a result, my total cost was about $1.00 (plus the software development time). You could probably obtain most of the components for $5.00 or less.
Well, best of luck with your construction and testing. If you develop some interesting applications for your light pen, I would appreciate the chance to hear about them:
Robert A. Peck
Manager, Technical Support to Advanced Manufacturing
MEMOREX CORP
San Tomas a( Central Expy MS 10-10
Santa Clara, CA 95052
(PAWcr Supply Cjmm,inj
Fig. 1. Basic Inexpensive Light Sensor
Q, Mounted in Tip of Pen
Rj Sensitivity adjustment, adjusted so that plus pulses are
present while pen is on screen opposite a part of screen which
is lit up.
LM3gOU Scnii
Output
Fig. 2. Typical Construction
ABOUT THE AUTHOR: Bob has a BSEEJmm Marquelle Unwersity and an MBA in Finance and Economics from Norlhweslern. He has been involved uiitli camputers since 1965, and has laut^ht microcomputer courses for Cogswell College in Sunnyvale, CA. He has authored three booklets on hardware and software for the 6502-based SYM-1 Single-Board computer. His assignment at Memorex involves arranging a smooth transition for new products from development engineering to Manufacturing. ©
42
COMPUTE!
March. 1981. Issue 10.
Getting The Most From Your Pet Cassette Deck
Editor's Note: There's much oj value herejor any cassette user, regardless of machine type. A couple of asides — the new recorders from Commodore (Ike VIC version) have tape counters. The second point is simply a comment on Mr. Sander's remark regardint; mail- order computer store tapes. . . most are quite reliable in business practice and quality control. RCL.
Louis F. Sander Pittsburgh, PA
PET owners not fortunate enough to own a disk spend many minutes, and ultimately many hours, waiting for the cassette deck to finish its work. SEARCHING seems to take forever, and we never know whether the search will finish with a READY, or with the dreaded ?LOAD ERROR. This article gives some practical advice on making that waiting time shorter, more productive, and less filled with anxiety. It is oriented toward the novice, and it con- tains much that has been explained before, although never to our knowledge all in one place. But even the most experienced PLAY presser should find something of value in it. We begin with a treatise on tape buying, proceed to information on recorder care and useful accessories, and end with a compendium of helpful hints for the recordist, librarian and programmer.
What Should You Feed A PET?
Standard cassettes can be had at prices from under 50^ each to over $5.00, and it seems impossible to know which ones to buy. Since the typical PET owner will end up with dozens of tapes in his library, knowing a bit about cassettes can be quite important — we want to be sure that ours will perform reliably, without contributing to the loss or ruin of valuable programs, but we don't want to pay extra for quality we can't really use. (After all, most of us are saving up for that disk system.) A careful study will show that there are three main areas of difference among cassettes, each of which we'll discuss here: playing time, mechanical construction, and type of magnetic tape.
First, playing time. Every cassette is marked with a number such as C-30, C-60, C-90, etc. The digits after the 'C tell how many total minutes of playing time there are on both sides of the tape. A C-30, for example, has two 15-minute sides, for a total of 30. Even though the longer tapes cost very little more than the short ones, for most PET owners the C-30 is the longest one to buy. One side of a C-30 will hold at least six long (8K) programs, and can be fully rewound in about 60 seconds. A C-60 will hold twice as many programs, but it gets tedious
to search through all that tape to find the one you're looking for; the rewind time is longer, too. The C-90's and above tend to be made with very thin tape that likes to break, or to let data leak through from one side of the tape to the other, either of which can ruin your program and your day. Probably the best size is the C-10, which is not widely available, but which holds one or two programs on a side, and which nicely minimizes search time.
Cassette construction is less obvious than the other two factors, but it does bear some discussion. Cassette housings range from sloppily molded boxes to finely assembled mechanisms with bearings and other anti-friction devices. Most housings are glued together, but some are assembled with screws. Many experienced PET users prefer the screw type, which can be taken apart for emergency untangling of tapes. (That can be a big factor when the fouled tape has your latest masterpiece on it.) Sloppy construc- tion is most often found in off-brand discount store cassettes, and it should be avoided, since a sloppy housing tends to let the tape escape and be mangled by your recorder. In general, the more expensive cassettes have better housings, and are easier to re- wind or fast forward, but you should have little trou- ble with any but the very poorest housing.?.
The finest and most expensive magnetic tape has a chromium dioxide (CrO^) coating, and should not be used in the PET. It requires special circuitry that the PET doesn't have, and its greater abrasivencss can cause rapid wear to lapc-handling parts. The next step down is extra-quality tape with a ferric oxide coating, usually selling for $2.50 -$5.00 or more per cassette; this tape is designed to give a very wide frequency response in stereo recording and playback. It will work fine in the PET's monophonic recorder, but its premium quality doesn't add much to performance, and for many people the extra qual- ity is not worth the extra price. The same can be said of the "certified" computer cassettes in this price range. Your PET doesn't need "computer quality" tape, or leaderless tape, so why pay extra for it?
Further down the line is garden-variety ferric oxide tape with a well-known audio or electronics brand, usually sold for under $2, or much less in multi-packs. For most PET owners, this is the best combination of price and performance. The tape is designed for monophonic recorders like the PET's, and it has the uniform quality usually found in well- known brands of any product. The widely available Radio Shack Concertape, starting at 3/$1.99| is a good example of this kind of tape. Also in this price range are the cassettes sold by mail-order computer stores that cater to PET owners. There are some real advantages to these cassettes — the price is right, they are available in the convenient C-10 size, and they are usually screw-assembled. But there can be risks, too. Some mail-order computer stores are
March, 1981. Issue lO,
COMPUTE!
43
THE STAR MODEM
From Livermore Data Systems
RS232 MODEM IEEE 488 MODEM RS232 GCin IEEE 488 coin
SALE $135
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$170
$280
STAR Modem is the price performance leader with a full 2 YEAR FACTORY WARRANTY.
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EBS Business System tor PET/CBM
Extremely comprehensive package to small Ixjsiness, Fully inlegraled mventtxy and accounts receivable system including invoices, packing slips, mall labels, statements, bank deposit slips, and 17 reports- Allows any ol 10 standard letters lo tie merged witti customer record info on either a selective or complete file tiasis Demo disk and system description available for S3.00.
Piper-Miti Word ProHuor $29.95
PET/CBM full featured 60 command system by Mk:hael Riley. Uses either tape or disk and any printer. Includes in-text commands, floating cursor, scrolling, etc.
6502
6502A
6520 PIA
6522 VIA
6532
2114-L450
2114-L200
2716 EPROM (5 volt)
TMS 2532 EPROM
41ie-2D0 II RAM
S-100 Wire Wrap
7.45 8,40 515 645 7,90
10/6.95 50/6.55
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10/6.10 50/5.75
10/7,40 50/7,00
3,45 20/3,35
4,15 20/3,95
9,90 5/9,45
100/615
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C-30 10/7.30 50/34.00 1 00/66.00
All otltei lengtlis available. Write for price list.
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4 PART HARMONY MUSIC SYSTEM for PET
Allows you to easily enter, display, edit, and p'3y4 part hamiony music Includes wfiole notes thm 64ths (with (Jolted and triplets}, tempo change, key signature, transpose, etc The KL-4 M unit i ncludes D lo A converter and amplifier (add your own speaker). KL-4M Mille BllN witk ITMM Pr*|nii 159.90
KM MM Pascal for PET $75
Subset ol standard Pascal with true machine language translator for faster execulm, 16K with tape or disk
EARL for PET [disk tile based) $65
Editor. Assembler, Relocater, Linker to generate relocat- able object code.
(ullFORTH-f lor PET/CBM $65
A full-tealurEd FORTH with exiensions confonnirvg lo Forth Interest Grotjp standards. Includes assembler, string process- ing capabilities, disk virtual memory multiple dimensioned arrays, floating point and integer processing.
commodore
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170 |
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255 |
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335 |
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170 |
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270 |
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Programmers Toolkit - PET ROM Utilities |
34,90 |
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43.00 |
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24.90 |
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105 |
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149 |
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The PET Revealed |
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Over 1000 programs and services available.
Ml PLOT Intelligent Plotter by Watanabe Instruments (Digiplot)
SPECIAL $1145
Has all intelligent functions (or producing grapfis and drawings including fl vector and 4 chaxacter commands. Solid and broken lines can be specified Character gen- eratorfof alpha, numeric, and symbola Characters can be rotated in 4 orientations, and can be 1 6 sizes Coordinate axes drawn by specifying graduation interval and number ot repetitions Parallel ASCII interlace, 11x17 paper
FLEX-FILE Ditl Bisi for CBM/PET $60
Random file handling system with Report Writer and Mail Label Handler. By Michael Riley
DISKS
(write for quantity prices)
SCOTCH (3M) 5W" SCOTCH (3M) B" Maxell 5W Maxell 8" Disks Verbatim 5 'A"
(add 1 .00 (or Vertjalim VerOatim 8" Obi Dens BASF 5'/." BASF 6"
Diskette Storage Pages Disk Library Cases
10/2.90 50/2.80 100/2.70 10/2.95 50/2.85 100/2.75 10/4.25 50/4.10 100/3.95 10/4.65 5O/4.50 100/4.35 10/2.45 50/2.40 100/2.35 5'/i" plastic storage box) 10/3.45 50/3.35 100/3.25 10/2.60 20/2.50 100/2.40 10/2.65 20/2.55 100/2.45 10 lor 3.95 8" -2.85 5%"- 2.15
EPSON MX-80 Pnnter S
STARWRITER Daisy Wheel Printer $1500
Centronics 737 Printer S79D
NEC Spinwriter- parallel $2500 XYMEC Hl-Q 1000 Intelligent Daisy Wheel S2150
Leedex Video too 12" Monitor SI 29 ZENITH OATA SYSTEMS
Zenith Z19 Terminal (lactory asm.) $735
Zenith ZB9 with 4eK $2150
SYM-1 S209
SYM BAS-1 BASIC or RAE-1/2 Assembler S 85
KTM-2/8Q Synertek Video Board $349
KIM-I (add $34 for power supply) $159
Seawell Motherboard - 4K RAM $195
Seawell 16K Static RAM - KIM. SYM, AIM $320
1 ATARI 800 $777
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Tfic 8086 Book lOsborne) $12,75
zeooO Assembly Language Programming SI 0.60
PET Personal Computer Guide (Ostane) $12.75
PET and Ihe lEEE^BB Bus (Osborne) $12.75
6502 Assembly Language (Osborne) S 9.90
Programming tlie 6502 (Zaks) $f0.45
6502 Applications Book (Zaks) $10.45
6502 Soflware Cookbook (Scelbi) S 9.45
CP/M Handbook {w/ MP/M) Zaks $11.95
WRITE FOR CATALOG.
Ada SI 25 per order for shijjping We pay balaiKcol UPS surface cn.iiges on all prepaid orders Prices iisied are on cish discount 0,1515 Hegul.ii prices slignily higher
44
COMPUTE!
March, 1981. Issue 10.
shaky operations with flaky quality control and fluky business practices. A good policy with these tapes is to try them if it suits you, but keep a close eye on what you get.
At the bottom of the list are the tapes you should avoid — the ones sold in discount stores, with brands you never heard of in audio or electronics. These are not much cheaper than Concertapes, and the tape inside is sometimes uneven and dirty. For most of us, the risk of getting junk is not worth the savings, so we should stick with something better.
Looking Out For Tape #1
Every tape head needs periodic maintenance, and the two on your PET are no exception. Experts recom- mend cleaning and demagnetizing tape heads after every ten hours of use, and you do yourself a big favor by following their advice. If you neglect these important tasks, sooner or later you'll begin to notice frequent LOAD ERROR messages, and you may permanently damage every recording you pass by the head. Tape head tolerances are measured in micro- inches, and it's very common for an invisible buildup of oxide residues to cause major signal losses, often leading to LOAD ERRORs. It's also common for recording heads to become magnetized after a period of use, especially if the recorder power is cut while doing a SAVE. A magnetized head partially erases every tape that is run past it. A dirty head can scratch tapes. Remember, a good head session takes only about 1010.^ minutes, and it clears your head for another 0Ag hours of use, so it's well worth the effort.
To start your maintenance program, get a bottle or spray can of tape head cleaner and a package of swabs. It's helpful, too, to get a small angled mirror, so you can inspect the heads while you work on them. Also get a head demagnetizer, of the type that plugs into the wall. (The cleaners and demagnetizers that look like cassettes are not as effective as the other types, and some poor ones can actually damage your head, so we suggest that you avoid them.) All these items can be purchased, often in kit form for under S20.00, at any good audio or electronics store. Sometimes you can borrow them from a friend who's into stereo or home computers.
When maintenance time comes, follow the in- structions that come with the cleaner, and thoroughly swab the heads, tape guides, capstan and pinch roller, all of which you can get to by unplugging the PET and depressing the PLAY control. If you can't identify which parts to clean, any knowledgeable stereo salesman can show you the corresponding parts on his equipment, and that should be enough to get you started. Next, demagnetize the heads, meticulously following the instructions that come with your demagnetizer. Particularly avoid cutting power to the demagnetizer when it is anywhere close to a head, or you may magnetize it yourself. Keep
your tapes at least 5 - 6 feet away from the demagnetizer at all times, or you may accidentally erase them. Remember that magnetic fields pass easily through everything but steel, and that a wooden desk drawer can hide tapes from you, but not from your demagger.
Useful Tape Accessories
The most useful tape accessory is a second recorder, but not the kind that plugs into the Second Cassette Port. You will gain many enjoyable minutes by using an extra recorder of any kind to search or rewind one tape while LOADing another. When searching, just play the tape until you hear the high-pitched leader tone, and start it right there on your PET. The buzzsaw sound after the leader tone is the actual pro- gram material. If your extra recorder has a tape counter, you can use it to keep track of program locations on the tape, and further lessen your SEARCHING time. If it has the Cue/Review feature, you can listen to the recorded material while rewinding or fast forwarding, which is also very helpful in finding things. If your recorder has a built- in microphone, make or buy a short-circuited plug to fit the MIC jack and cut out the microphone; that will let you erase selected areas on your tapes, which is useful if you're recording over other material and getting a lot of VERIFY ERRORs. Without the built-in mike, you don't need the shorting plug.
The extra recorder, used in audio mode, can help you type in programs from COMPUTE! and other sources, too. Just read the program aloud into the microphone, carefully enunciating every comma and semicolon, then play it back to yourself and type in the program as you hear it. This is a super method for proofreading programs that don't work.
Another useful accessory is a bulk eraser, for quickly erasing tapes when you want to re-use them. Mine is a Nortronics Sound-Off, a permanent magnet unit that works by just sliding the cassette through a slot. Most of them plug into the wall, and work like head demagnetizers, but on a grander scale. Be careful with bulk erasers — they create a strong magnetic field that can erase your good tapes if they are anywhere close by.
The stores have many other items you might find worthwhile. Radio Shack has a slick manual rewinder. The Sams book "Tape Recording for the Hobbyist" and the Nortronics "Recorder Care Manual" arc good sources of useful information. Ad- vanced tape hobbyists may also like to have a tape splicer and a head alignment tape, but these are beyond the needs of most of us.
Tape Handling Tips
1. Running new tapes back and forth a few times before using them will minimize binding and breakage. Erasing tapes before re-use will minimize read errors due to "junk" on the tape. Breaking out
March, 1981. Issue lO.
COMPUTE!
45
Announcing
from the publishers of
COMPUTE!
The Journol For Progressive CompirUng
Small System Services, Inc. is pleased to announce publication of a new quarterly magazine exclusively for the new VIC® connputer.
Horn* «j-id CduoMtional
COMPUTING! , editorially and physically of the same high quality as COMPUTE!, will premier with an April/May/June issue. Every issue will be full of useful applications material and learning aids.
Our staff of Contributing Editors already includes sonne of the best authors in the industry: Jim Butterf ield, Tory Esbensen, Harvey Herman, and David Thornburg, to name a few.
Horrw »nd Educatloriat
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Reserve your f irat iseues now by filling out the form below.
r.
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Addrese inquiries and correspondence t;o:
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Editor/Pubiisher
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46
COMPUTE!
March. NSl. Issue 10.
the write protect tabs on a cassette will keep you from writing over programs by mistake. Covering the write protect hole with tape will override the protection.
2. Keep your tapes clean: Rewind cassettes before putting them aside, and never touch the magnetic tape itself. Always use plastic cassette boxes; the soft ones are cheaper and tougher, but the hard ones are prettier. (I use hard boxes for master tapes and soft ones for working copies.) Keep your cassette boxes in metal containers; stray magnetic fields are everywhere, especially around motors and transformers, and they can damage unprotected tapes.
3. As soon a.s you SAVE a program, label the cassette with the program name. Half-inch masking tape makes an easily removable label for cassettes, and also fits perfectly on the edge of hard or soft cassette boxes. Half-inch Scotch Magic Tape makes a neatly erasable label for the same places.
4. A IK program takes about 35 seconds to SAVE, VERIFY, or LOAD. A 4K program takes about 90 seconds, and an 8K program about 150 seconds, or 2}^ minutes. The practice of SAVEing each program twice on the same tape will keep you happy in the face of minor malfunctions; the practice of keeping
master copies on a separate tape in a separate room will keep you happy in the face of disaster.
5. There is a small but real danger of write-through when programs arc recorded on both sides of one piece of tape. You can avoid it by using only one side of your cassette, or by using both sides and recording no further than mid-tape. I usually SAVE one program twice on each side of a C-10. That way I have minimal search and rewind time, conveniently located second copies of each program, and no overlapping.
6. During program development, SAVE your work frequently, so you'll have something to work with after an unanticipated NEW or system crash. To keep track of the different versions, make the date and time of the SAVE an integral part of your pro- gram's working name: "02141015SPACEWAR" fits into the 16-character limit, and indicates that this version of SPACEWAR was SAVEd on 2/14 at 10:15 AM. If there's ever a question, it will be obvious that "02141 300SPACEWAR" is a later version, and that "01312200SPACEWAR" is an earlier one.
That's the end of one user's notes on saving time and grief with your PET's tape deck. There must be many other good ideas on the subject. If you have some, let us know about them.
Announcing the magazine specifically for the educational user of microcomputers.
Edunational bomputer
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March, 1981. Issue lO.
COMPUTE!
47
PET
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The'SiG tour programs were (Jn>uJDp«d bottia-a a tulocia.1 lor Ihu^ planning la visit sCasino',3r(l iii,anlinf] id leisrn \a playcorrei meiKSi lor ihe ^eriaLis-garntile'r to dm'dDp drd thraougfily lesT a c^rribling 'syafem' under aciijjtl Cas.rno condilJGrs. All txiiii Dplions available in Ihe Casino {ji irid: UGM Gianct Hglil in tas Vegas have [>een i.-icsrporaled into ihese piog.rarns Ful FiavD&evn used la sdow lh« cardft tw^ng d»all, Lh-e Houl«lle Wheal ipirning, andthC' D4C« being IhraA'D in ordni ic inci
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ATARI ATARI SALE
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I 7.« S 7.9^
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HARDWARE |
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800 COMPUTER |
$825 |
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400 W/16K |
$495 |
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$400 |
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820 PRINTER |
$410 |
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MICK0LINS-8a |
$600 |
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5" MEMOREX DISK |
10/S30 |
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810 DISK DRIVE |
S5S0 |
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32K MICROTEK RA^ |
$195 |
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32K AXLON RAM |
S275 |
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$155 |
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$95 |
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S185 |
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LIGHT PEN |
569.95 |
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815 DISK $1350.00 |
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SOFTWARE |
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20% |
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