COMPUTETs

February 1984 'S lssue8Vol.2, No. 2

02220 CI. 95 UK S3.25 Canada

For DwnerVAhQ Dsers Qf Commodore ViC-20" And 64" Personal Computers

ASTRO PANIC!

Dodge the diving alien saucers and fire your laser wisely. But don't lose control — there's no time to relax. A colorful arcade-style qame written entirety In nnachine language for the 64.

71486"02220"

02

Haunted Mansion

An Acfion-Sfrafegy Game For VIC And 64

Elude the ghosts and bats — ana especially

luae The gi

ats — ana ( the demons — as you wind through the cor- ridors of the haunted nnansion. For children of all ages.

Multicolor Character Generator

.,,„,wrff/if///////f////ff//f//tfn,,..

A VlC-20 utility that takes the tediunn out of program- ming and design- ing multicolor cus- tom characters.

A connputer can do a lot to improve reading speed. When used properly, this pro- gram for VIC and 64 is a valuable educa- tional tool.

Ms9 In This Issue

Bits & Bytes: PBS's New Series

How To Use Arrays

Typing Derby

Power BASIC:

Auto Line Numbering

The Challenge:

match lUlts uiKh the mind 6aflies

from Broderbundl

DPERATIOH<

i^

is the ultimate weapon in this unique war game. Strategy, not force, is the i<ey to victory as you move your battalion through a series of testing skirmishes and battle actions. Your ability to command, to give orders, to move your troops skillfully determines the success of your assault and combat operations. Operation Whirlwind requires the concentration of chess— a typical game may take between one and three hours— and the

ability to master the many tactics of wag- ing a full scale war. How well you can focus your strategic energies will decide whether your vic- tory is Question- able, Marginal, Tactical, Strategic or a Breakthrough. A great game for the thinking game player. Available on disk.

Pit your concentration against another player or the computer. Here's a puzzle game that will keep the whole family bemused, befuddled and play- ing happily for hours. A grid of 36 numbered boxes con- ceals an animated menagerie of colorful characters, creatures and objects. The object of the game is to match identical squares and then solve a hidden word puzzle. There are many game variations with puzzles that are frontward, backward, or scrambled. Matchboxes. It's the most memorable memory game you've ever played! Available on disk and cassette.*

OPERATION WHIRLWIND AND MATCHBOXES ARE AVAILABLE FOR THE COMMODORE 64 AND ATARI

HOME COMPUTERS, commodore m ami atj^ri bao tnl(leniafks,Q( A»fi,,lne.,,*uiit, Commnttora Elactronics, Lid., rsapectively, '!w!lJ:tiJJiHtL'MW:lwImliiiilhiii!ilij:Jtriiiii,

'Cassette on Atari computers only.

BroderbundSofhuare

Discover the Difference

Richvale

Telecommunications,

LTD.

Distributed by:

Warehouse 1, Inc. Computer Marketing DES-Data

Eastern u.S 800-253-5330 Services, Inc. Equipment Supply

Western 50&25S<3Q56 800-222-0585 213-923-9361

Blue Sky Software Ashland Office Center Evestiam & Alpha Avenues Voortiees, NJ 08043 609-7954025

Also available tor !t>e IBM-PC.

Script M, Commodore 64 and IBM-PC ore registered trademarks ol Rictwole CommunlcaHons LID,, Commodore Electronics Limited, and Inlemotionol Business Mochlnes. Corp. respectively.

SPINNAKEirS LME OF EARLY LEARNING GAMES

ISGROWING

AS EAST AS YOUR

CHILD^MIND.

Watching your kids grow up is a lot of fun. But making sure their minds grow as fast as their bodies is even more rewarding. That's where we can help. With a growing line of Early Learning Programs that are not only lots of fun to play, but also educational.

Some of the games you see on these two pages help exercise your child's creativity. Others help improve vocabulary and spelling skills. While others

improve your child's writing and reading abilities. And all of them help your child understand how to use the computer.

So if you're looking for computer programs that do more than just "babysit" for your kids, read on. You'll find that our Early Learning Programs are not only compatible with Apple® Atari® IBM® and Commodore 64™ computers, but also with kids who like to have fun.

A trip through ALPHABET ZOO™ Ages 3-8

It's a race, it's a chase. It's Alphabet Zoo, the exciting game that will have your kids zipping through the maze, after letters that fit the picture on the screen.

And at the same time, your kids will be learning the relationship of letters and sounds, and sharpening their spelling skills. So they'll be laughing and learning at every turn.

Apple. [BM arxJ Atari are registered iraderT^rks of Apple Computer. Inc., Intjematicnal Business Machines Corp. and Atari, 1^. resp«rtive!y. CoriimrxJarE &1 is a tradc-mar1< gf Gommodore EiKtronies Umited. ■© 19S3HSpinrjktr Software Corp. All nrjMtE reser^Kj.

V

FRACTION FEVER'." brings fractions into play. Ages 7 to Adult.

FRACTION FEVER is a fast-paced arcade game that challenges a child's understanding of fractions. As kids race across the screen in search of the assigned frac- tion, they're actually developing a basic understanding of what a

fraction is and of relationships between fractions. They're even discover- ing that the same frac- tion may be written in a number of different ways.

All in all FRACTION FEVER encour- ages kids to learn as much as they can about fractions - just for the fun of it!

KINDERCX)MP;™ Numbers, shapes, letters, words and drawings make fun. Ages 3 to 8.

KINDERCOMPisa game that allows very young children to start learning on the computer, it's a collection of learning exercises that ask your children to match shapes and letters, write their names, draw pictures, or fill in missing numbers. And KINDER- COMP will delight kids with

colorful rewards, as the screen comes to life when correct answers are given. As a parent, you can enjoy the fact that your children are having fun while im- proving their reading read- iness and counting skills.

DELTA DRAWING J" Have fun creating pictures and computer programs. Ages 4- Adult.

Kids love to draw. And DELTA DRAWING Learning Program lets them enjoy creative drawing and coloring while they learn computer program- ming concepts. As they use simple commands to put lines and colore in

their drawings, they're actually writing com- puter programs!

With DELTA DRAWING, even kids who have never used a computer before can learn to do simple programming and build an understanding of procedural think- ing. It's easy, clear, and lots of fun!

^ffflMNER

Dtalu (tor: Apple. Atari. IBM, ConmaJore 64, CartTtdg«a for: Atari, Commodcre €4

We make learning fun.

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SAVEHEWYDS

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It was as peaceful a day as New Yoik em gets, when stiddenty the sky went dark and a monstrous dfoning noise tilted the ait Hordes ol grotesque alieiis were swooping down from all sides, hiting into the Big Apple as // they hadn t eaten for days. They were laying eggs. too. Horrible slimy things that got down into the subway tunnels and began clawing their way up. If ai}yone was going to save the city, it would have to be me. / leapt into my rocket and began blasting away I thought I stood a lighting chance, but fuel's running low. . . another wave of invaders on the horizon . . . signing oil. .

SAVE NEW YORK':' Form Commodots 64.

A T I V

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P0bnfary1984 Vol. 2, No. 2

"Bits And Bytes": PBS's New Computer Series Kathy Yakal

The Inner World Of Computers, Part 4: Tiie Inside Story Tom Prendergasf . .

Getting Started With A Disk Drive, Part 4: Data Files Charles Brannon

Top 40; Comparing The Software And Record Industries Kathy Yakal

Inside View: Steve Punter, The Programmer Behind WordPro Selby Bateman

26

34 44 55 58

Haunted Monsiod Calvin Overhutser 62 V/64

Astro- PANIC! Charles Brannori 68 64

React Don Whiiaker 72 V/64

Checkers Fred Hambrecht 90 V/64

Fourth Encounter For VIC Tony Roberts 1 06 V

Suspended for Commodore 64 Dan Carmichael 108 64

Cassette Interface For VIC/64 A. C Pendleton 118 V/64

Attack Of The Phantom Karate Devils For Commodore 64 Gregg Keizer 119 64

Computing For Families: The New King Of The Mountain Fred D'Ignazio 76

Speed Reader Phil Geiser , 82

Typing Derby Carlos Esteves 86

VIC Piano Brad Bascom 94

Cassette Cotaloger Kevin Gough 9B

Homonym Practice Michael A. Tyborski 102

V/64

V/64

V

V/64

V/64

IROGRAMMI

Multicolor Cliaiciclei Gonerotoi For VIC-20 Bill Gates 124 V/64

Machine Language For Beginners: Tapping Into BASIC Richard Mansfield 129 V/64

The Beginner's Corner: String Variables And Functions C. Regena 132 V/64

How To Use Arrays Don Stauffer 1 38 V/64

Power BASIC: Auto Line Numbering Jeff Young 146 V/64

The Editor's Notes Robert Lock , . 6

Gazette Feedback Editors & Readers 10

Simple Answers To Common Questions Tom R. Halfhill 20

HOTWARE: A Look At This Month's Best Sellers Kathy Yakal ..'.[ 54

Horizons: 64 Charles Brannon 1 50

VICreations: A Window Info The VIC-20 Dan Carmichael 152

News & Products 157

64 V

^PROOIIAM IISTJMO'

A Beginner's Guide To Typing In Programs 160

How To Type In COMPUTEl's GAZETTE Programs 161

The Automatic Proofreader 1 62

MLX: Machine Language Entry Progrom For Commodore 64 And VIC-20 Charles Brannon ... 163

The Bug-Swotter: Modifications & Corrections 164

Product Mart 165

Program Listings 168

COMPLITEI's GAZETTE For Commodore Author Guide ...............191

Advertisers Index 1 92

* = General,V = VIC-20, 64 = Commodore 64,

V/64

V/64

CUMl'Ultri Gizcllv is fiuhlisticij Iwclvi; limes iMcli ye.ir by COMPUTII Puhlic.iliiiiis, Inc., I'lisl Office Bnx 5406. GrVL'nsboro, NC 274U3 L'SA. I'hinu' i')\'i)275-WW. Editorial oflici's arc hxaltd nt 505 Edwardia Drive, Crifrmbiirii, N'C 2740V. Diinifstic siihsfririiiims; 12 issues. $20. Bfrd subscription urdiTi) ur chaiiEe of .iddri'ss (P.O. Form 3B7<)) lu Cirtul.iliun Depl., COMPUTLrf Cazellf, P.O. Box 5406, Cn-fiistrnm, NC 27403. Second class application pvaditiR at Cri-enstmix), NC 27403 jtid .idJition.il nioilinj; iiffici's Priliri' amli-nti aijiyiijiht i' I Wl i>v COMPUTll Piililic.ilitiii-,. Int All rinliis [esi-ncd. ISSN 07.17- .1716. 53£]Od.

COMPUni Publicitioni, tn{„ Out of Ihr ABC Publilhlng CompjniH: ABC Puhliihlng, Prtlidfnt. Robtrt C, Burton; 13J0 Avmutof iht Amfricw; New York, Ni-w Ymk 10019.

THE EDITOR'S

We welcome Lance Elko as editor of COMPUTEI's GAZETTE. Tom Halfhiil, former editor of the GAZETTE, has moved into the position of editor of our newest magazine, COMPUTE!'s PC & PCjr. Lance, a native of Philadelphia, joined us last May as an assistant editor in the magazine division, eventually becoming assistant editor of the GAZETTE. As editor of the GAZETTE, Lance will con- tinue to bring you the same clarity of style and solid content that you expect in the GAZEITE.

Exciting news for those of you who've grown tired of typing in our extensive applications and games software. Beginning with the April issue of the GAZETTE, we'll have monthly disks available that contain all of the software printed in each issue of the magazine. We've been working on this task for some months now, with two primary goals in mind. First, we knew we had to insure the qual- ity of the disk that's delivered to you each month, and second, we wanted to find a way to do this as inexpensively as possible. Our goal was to make it so easy to accomplish that it would be- come a truly broad-based method of distribution of our highly useful .software.

We'll give you full details in the March issue of the magazine.

but for now here's where we are. Subscribers will be able to enter a six or twelve month sub- scription to the disk series. The disk corresponding to each issue of the magazine will be released in time to arrive by first class mail as close as possible to the arrival date of your magazine. The magazine will contain all of the descriptive information and articles as well as the documen- tation for each program. Full listings will, of course, continue to appear in the magazine. The magazine itself will not c/frtM^v; we'll simply have all of the monthly software available on disk as well. For those of you who wish the convenience of not having to enter programs, we'll have the solution.

You regular newsstand buyers will have the option of ordering each month's disk when you purchase the magazine. Individually ordered disks will be available for ship- ment to individual orderers ap- proximately one week after the magazines arrive at dealers and newsstands. Disks will not be available for sale at retail outlets.

Here's how the disk sub- scription will work. If you wish to start with the April disk, you'll need to send in the special re- newal card that will be bound in the March issue. You will have

to do this as soon as you receive your March issue of the magazine. This card will do two things. It will extend your sub- scription period to coincide with the disk subscription period, Also, it will activate your disk subscription to insure that you receive the first disk issue. Cur- rently, the "alternate media" subscription will be available only on disk. Note that if you order a one year disk subscrip- tion, and have only eight months left on your magazine subscrip- tion, it will be necessary to ex- tend your magazine subscription by four months to match the twelve month disk subscription. The cost of the magazine sub- scription is not included in the cost of the disk subscription.

We'll have all the final de- tails in the March issue. Re- member, it will be very important (if you wish to be included in the first run of April disks) to com- plete and return the appropriate card immediately upon receipt of your March issue. We're cer- tain that you'll find the disks quite convenient.

Editor In Chief

6 COM PUTEI's GazettB February1984

If you could live on half

your incomct just tliink what

you could do with the other haJf f

1

ifevSt>'le Budgeting!

le first budget planning system that considers all your needs.

others have done it . . . so ceui you.

Dr. Harper Roehm. the author of Spending Less and Enjoying It More

(the McGraw-Hill book that pro\ides the ba.sis for this system), designed lifestyle Budgeting when his income was cut In half due to a career cheinge from corporate auditor to university professor. As a result, his family has lived comfortably, fulfilling their 'Nvants" as well as their "needs" for over 20 years.

We show you "why" as well as "how." Lifestyle Budgeting is the first com- plete budgeting package to include an easy-to-understand book explaining the behavioral aspects of successful budgeting aji well as software to handle the mechanics. It takes a practical approach, showing you not onl>' how you're spending your money, but wh>' ... so you can identify your true priori- ties and plan for them.

Plaiming is the key. Lifestyle Budgeting's software is a forecasting and modeling lool, not a checkbook balancer. It will track your spending patterns. ideiHif>1ng where you're wasting valuable funds. Losing that information, and your family's priorities, it will show you specifically how to project and plan future costs.

Little time, and no accounting experience required.

Unlike most budgeting systems. Lifestyle Budgeting does not require detailed expense records, it will only take a couple of nights to set up and then only one or mo hours a month to monitor. And ... a big plus ... Lifestyle Budgeting is written for you, not your accountant.

"^I

-■. <■'

m^^^m

.sas^

use Luestyle Budgeting on your persona] computer.

Since Lifestyle Budgeting is some- thing everj'one needs, versions are available for IBM. Apple, Commodore. Atari and Coleco personal computers. Get control of your money today! Lifestyle BudgetJUig will be available through your local computer retailer starting in Februar>' ... but why widt? You can order the complete package today.

Order now!

Call 1-800-547-1 565.

In Ohio CaU I -51 3-435-2355.

DcaJtr lni|ulrlrs wcJconted.

/ es! I'd like to know how lo^etjjp a [liveable budget.

PleasQ st'nil me .

- copies

iir Utcstylc DudgeUno (IncIuiUng ihe McCraw-ltHl book Spending less and Enfoyijtg IS More, and the a«:ompan>ing soft^^a^c and manual! ai 549.9-5 each plus S3 for shipping and hantllmo- (In Ohio add 6* .>!alt's tax.)

Name

Address

aty

State

Zip

T>TW computer Model

Qietk or money order enclosed D

VISA or MasierCard No.

Expiration Date

Bank No. (MMtt'rCiu-tll

Si(in.iture

RtlLirn t'oupcn and jwynwiit ui

■ Corporation

culvefm

Cutvchn COTpiirniUin. l.irc.^'li' Uudnctlngi P.O. lloi sort. dMltcrvillf, (III ■tSl.'i').

COMPUTE! Publications Jnc®

Address all advertising materials to: Patti Williams, COMPUTEi's GAZETTE, 505 Edwardia Drive, Greensboro, NC 27409

'Gary R. Ingersoll »r In Chiaf Uobcrt C. Lock Dir*ctttr of AdmlnlflraHoM Alice S. Wolfe S««(or Editor Riihard Mansfield Managing Editor Kathleen E. Martinek Art/Dvsign Mrvctot' Georgia Bikas Davis

Etniorial

Lance Elko, Gazette Editor; Tom R. Halfhill, PC and PCjr Editor; Stephen Lcvj'. Editor, COMPUTEt Books Division; Gai! Walker, Production Editor; Oltis R. Cowper, Technical Editor; Charles Brannon, Program Editor; Tony Roberts, Assistant Managing Editor

JUslstant Bdltori

Dan Carmichael (Submissions), Gregg Keizer (Books), John Krausc (Technical), Todd Heimarck, Robert Sims (Publications); Selby Bateman (Features), Kathy Yakal, Editorial Assistant (Features), Randall Fosncr, Editorial Assistant (Books)

Saira Officttf,

New i jigland

Mid-Atlantic

Southeast

Midwest

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Northern CA

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New Mexico

Colorado

Leslie Jessup, Cindy Mitchell (Publications), Janice Fary, Debbie Bray (Books); Harry Blair, Illustrator

Op«rati«iis/Ciistoni«r Safvice

Carol Lock, Man.if^er, Pattv Jones, Customer Coordinator; Assistants: Chris Patty, Chris Gordon; Fran Lyons, Dealer Coordinator; Assistants: Gail Jones, Sharon Minor

Cuttoitwr Service Stuff

Dorothy Bogan, Supervisor; Rhonda Savage, Lisa Flaharty, Aniia Roop, Sharon Sebastian, Debi Goforth, Jenna Nash; Elizabeth White; Operators: Cassandra Robinson, Mary Sprague Jim Coward (Warehouse Manager), Larry O'Connor, Chns Cain, Dai Rees, Jack McConnell

Data Proceulng

Leon Stokes, Manager; Joan Compton, Assistant

A«ouitt{iig

Paul J. Megliola, Manager; James M. Hurst, Comptroller; Assistants: Linda Miller, Doris Hall, Jill Pope; StalFf: Anna Harris, Emilic Covil, Anne Ferguson

Advefffistng Sales

Patli Williams, ProducHon Coordinator; Bonnie Valentino, Accounting Coordinator; Rosemarie Davis, Sales Assistant

Sales Representatives

Jerry Thompson 415-348-8222

Phoebe Thompson 408-354-3553

JoAnn Sullivan 619-941-2313

Ed Winchell 213-37H-8361

Harry Blair 919-275-9809

Jules E. Thompson, Inc. National and Canadian Sales Representatives 1290 Eloward Avenue, Suite 303 Burlingame,CA 94010

6 COMPUTEI's Gazelle February 1 984

The Thompson Company

fi] 7-720- 1H88

2i2-772-t)933

919-275-9809

312-726-6047

713-731-2605

408-354-5553

41 5-348-8222 or 408-354-5553

619-941-23 1 3 or 213-378-836 1

619-941-2313

213-378-8361

303-595-9299

Idlterial Ptmi

Patrick Parrish (Svipervisor), Gregg Peele (Assistant), Jeff Hamdani, Kevin Martin, Chris Poer

Technical Assixtant

Dale McBane

Programming Assistants

MarkTuttle, David Florance

Copy Editing/Proofreading

Juanita Lewis (Assistant), Becky Mall, Linda Shaw, Martha Banks

Administrative Staff

Vicki Jennings, Laura Ma cFad den, Julia Fleming

Associate Editors

Jim Butterfield (Toronto), Harvey Herman (Greensboro), Fred DTgnazio (Roanoke), David Thomburg (Los Altos), Bill Wilkinson (Cupertino)

Prodvction

Irma Swain, Assistant Production Manager; De Potter, Mechanical Art Supervisor; Terry Cash, Debi Thomas, Typesetting

COMPUTE! Publications, Inc. , publishes

COMPtmi COMPUTE! Books CQMPUTtVs OaMtf

Corporate Officet

505 Edwardia Drive, Greensboro, NC 27409

Moiling Addresss

Post Office Box 5406, Greensboro, NC 27403

Telephone: 919-275-9809

Office Hours: 8:30 AM to 4:30 PM Monday- Friday

Chief Execwifve Officer Robert C. Lock

President Gary R. Ingersoll

Director, Finance & Planning Piiul J. Megliola

Comptroller Ja m e s J , Hu rs t

Executive Assistant Debi Nash

Assistant Carol Diikerson

Subscription Information COMPtmi's Goxoite tiraulaHon Dept. P.O. Box S40«, Greensbeve, HC 27403

TOiXFREE

Subscription Order lino

800-334-0868

bi HC 9i9-37B-9e09

COMPUnl's GccEvtl* Subscription Rata*

(12 issue Year|t US {one year) $20. Canada, Mexico and Foreign Surface Mail $25. Foreign Air Mail $45.

The coMruTEVs G^n^v^ subscriber list is made available to carefully screened organizations with a product or service which may be of interest to our readers. If you prefer not to receive such mailings, please send an exact copy of your subscription label to: comi'uti;!'* GAZCTTK, P.O. Box 961, Farmingdale, NV 11737. Include a note indi- cating your preference to receive only your subscription.

Authors of manuscripts warrant that all nnaterials submitted to COMPUTEI's GAZETTi; aro Original materials with full ownership rights resident in said authors. By submitting articles to computers CAZKTrE, authors acknowledge that such materials, upon acceptance for publication, become the exclusive property of COMPUTEI Publica- tions, Inc. No portion of this magazine may be reproduced in any form without written permission from the publisher. Entire contents copyright © 1983, COMPUTE! Publications, Inc. Rights to programs developed and submitted by authors are explained in our autnor contract. Unsolicited materials not accepted for publication will be returned if author provides a self-addressed, stamped en-velope. Where programs are included in an article submission, a tape or disk must accompany the submission. Printed listings are optional, but helpful. Articles' should be furnished as typed copy (upper and lowercase, please) with double spacing. Each article nage should bear the title of the ariicle, date, and name of the author. COMPUTIl Publications, Inc., assumes no liability for errors in articles or adver- tisements. Opinions expressed by authors are not necessarily those of COMPUIi! Publications, Inc.

PET, CBM, ViC-20, and Commodore 64 are trademarks of Commo- dore Business Machines, Inc., and/or Commodore Electronics Limited. Other than as an independent supplier of quality information and services to owners and users of Commodore products, COMPUHI Publications, Inc., is in no way associated with Commodore Business Machines, Inc., or any of its subsidiaries.

WordPro 3 Plus764

The #1 Selling Word Processor for the Commodore 64^

■m

W?-

WordPro 3 Plus'764 and SpellRight Plus'" provide a total word processing solution for the Commodore 64"" which gives you:

* Sophisticated Word Processing

* Built-in Mail Merging for Form Letters

* Math Functions for Column Totals

* Fast and Complete Spell Checking via SpellRight Plus

* A Super Value {two programs) for Only $99.95!

WordPro and SpellRight are both specifically designed for the novice user with no computer or word processing experience whatsoever. And witti over 40,000 WordPro versions sold, you can be sure that WordPro is a very sophisticated word processor loaded with powerful features including: Transfer, insert, Delete, and Rearrange Text, Auto Page Numbering, Math Functions, Headers, Footers, Global Search and Replace, the Ability to Create Multiple Personalized Letters and Documents, and much more. WordPro can create documents of virtually any length and will print up to 165 columns wide. You get all of this PLUS fast and complete spell checking using SpellRight PI us I

SpellRight Plus locates and highlights misspelled words and then allows you to quickly correct the misspellings — improving the quality of your letters and reports.

And, best of all, WordPro and SpellRight's powerful arsenal of features can be put to use almost immediately — by even the novice user. So whether you're a student, professional writer, in business, education or a hobbyist, you'll quickly become a WordPro Pro!

Both WordPro and SpellRight Plus are also available separately at popular computer outlets nationwide.

Invest In the best . . .WordPra Plus. In a class by Itself.

Professional Software Inc.

51 Fremont Street Needham, MA 02194

(617) 444-5224 Telex: 951579

Dealer and Distributor inquiries are invited.

WordPro 3 Plus'*/64 and SpellRight Plus" are trademarks ot Professional Sohware Inc.

Tfio WordPro Pija Series was designed and written tjy Steve Punter ot Pro-Micro Software Ltd.

SpellRlgfit Plus was designed and written b/ Dwiglit Huti and Joe Spatafora ot SpellMaater Systems, Inc.

Soma printers may not support certain WordPro 3 Plus functions and/or require an Interlace. Please check witti your dealer.

Commodore 64" is a trademark of Commodore Electronics Ltd

GAZETTE FEEDBACK

EDITORS AND READERS

Do you have a question or a problem? Have you discovered something that could help other VIC-20 and Commodore 64 users? Do you have a comment about something you've read in COMPUTEi's GAZETTE? We Want to hear from you. Write to Gazette Feedback, COMputei's gazette, P.O. Box 5406, Greensboro, NC 27403.

Limiting MemoiY

I would like to know why some of your programs limit the top of memory (with a POKE 56, xx). It seems to me that these POKEs could be left out of the program,

Mike Carroll

hi both the VIC ami 64, memon/ locations 55 auil 56 arc used ns a pointer to the top of BASIC memonj. This means that they contain the address (plus one) of the highest memory location that can be used by BASIC. There is an equivalent pointer to the bottom of memory (locations 43 and 44). You can find out where BASIC begins and ends with these formulas:

print PEEK(44)»256 + PEEK(43): REM BOTTOM OF

MEMORY PRINT PEEK(56)-256 + PEEK{55>: REM TOP OF

MEMORY

The reason for changing one of these pointers is fairhj straightfonvard . When you write a BASIC pro- gram, the computer stores it in Random Access Memory (RAM) beginning at the address in the bottom of memory pointer. Sometimes you need to create a safe area of memory ivhich BASIC cannot disturb, as, for example, when you leant to include a machine lattguage sub- routine or a redefined character set luith your BASIC program. You could create this safe area by raisiiig the bottom of memory (increasing the value of the pointer in locations 43 and 44), but it is far more common to lower the top of memory by changing the values in loca- tions 55 and 56. If you want to reserve some even mul- tiple of 256 bytes (called a page of memory), you need POKE only location 56. The POKE to location 56 works by fooling BASIC into thinking that RAM ends before it really does.

Actually, VIC and 64 programs which limit the amount of memory available to BASIC ivith a POKE to location 56 should also POKE location 52 with the same value. The reason for POKEing location 52 is more subtle, and requires an understanding of how Comtno- dore BASIC manipulates variables. Briefly, as a BASIC

10 COMPUTEi's Gazette February 1984

program runs, it tends to put variable values into the area of memory starting at the end of the program and ending with the address contai}ied in locations 51 and 52. The address in locations 51 and 52 can be thought of as the "top of memory for variable storage" pointer. If you don't want BASIC variables to destroy the data you store at the top of memory, you nuist POKE location 52 along with 56.

An example of this is the "Spike" game fCOM- PUTEl's GAZETTE, December 1983). That machine lan- guage program resides at the top of the BASIC memory area, but no POKEs loere made to protect it. As you typK in the numbers for Spike, the variables for the BASIC "MLX" program ovenurite your typing. Spike can be protected from BASIC by moving the top of mem- ory and the top of variable storage to below the start of the machine language. Do this by typing POKE 56,J28:POKE 52,-158:CLR before running MLX.

Note that memory restrictions created by POKEing locations 52 and 56 remain in force even after you type NEW or hit the RUN /STOP and RESTORE keys. Turning the computer off and back on loill restore the normal values.

How The Computer Stores Data

I'm confused about how the computer stores DATA statements for machine language pro- grams. You published a program with DATA 157, 0, 4 (STA 1024, X). Does the computer store in hex? I know STA uses a 16-bit address and that 1024 (decimal) = 50400 (hexadecimal).

Kenneth L. Marvin

The computer stores numbers only in binary. When you POKE a nundm- into memory, you use decimal, but the number is stored as binary (base two); the bits are on or off. At the lowest level, everything is either a one or a zero.

Random Access Memory (RAM) contains many on-off switches, which by themselves do nothing. The computer also contains a Central Processing Unit (CPU) which interprets certain bit patterns as machine lan- guage instructions. This is what gives it the power to compute.

When the CPU sees WOUIOI , it interprets it as the instruction STore Accumidator. The computer only cares about the binary number. It's up to us whether we zoant to interpret the number as WOUIOI (binary) or as $9D (hexadecimal) or as 157 (decimal).

Sec the series of articles "The Inner World Of Com-

I!

#\

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Abbreviating The IF-THEN Statement

I have run into what seems to be incomplete IF- THEN statements like this:

20 IF A THEN 100

I don't understand what the IF is checking, I have seen this in more than one program, but I can't figure it out.

Guy Richards

IF-THEN statements are used to test for a certain con- dition and to talie action only if the condition is true. They operate logically: IF (something is true) THEN (do somethitig). When i/ou use IF-THEN, you are checking the truth of an expressioti (a variable or equa- tion). IF the condition is true, THEN the program ex- ecutes a command.

IF X =5 THEN Y = 15 IFX = 5THEN PRINT ' IFX = 5THEN200

GAME OVER"

The three examples above check the value of vari- able X. If X equals 5, different actions are taken. In the first example, ifX = 5. then the value ofY is set to 15. In the second example, the line performs a BASIC com- mand (PRINT) ifX = 5. The third example could have been loritten IFX = 5 THEN GOTO 200, but it ivorks just the same zi'ithout the GOTO.

In the line mentioned in your question, the IF statement is checking the variable A. IF A (is true) THEN (GOTO) 100.

How can a variable be true or false? The computer decides that if a variable has a value of zero, it is false. If the variable has any other value, it is true. When the BASIC interpreter sees IF A (without an equation), it checks to see if A is zero or nonzero. When you see a line like IF A THEN 100, you can read it as IF A (does not equal zero) THEN (GOTO) 100.

Some beginning programmers inadvertently tnake mistakes when they use IF-THEN as part of a multiple- statement line. When an IF-THEN isfolloxoed by a colon and another BASIC statement, the BASIC state- ment becomes part of the THEN section. Watch out for lines like this:

10 IF A<1S THEN 100: PRINT"YOU HAVE A VERY GOOD SCORE!"

The computer checks to see if variable A is less than 15. If it is, it goes to line 100. If it is not less than 15, it zvill skip the rest of the line. The program will never get to the second part of the line (the PRINT com- mand). If an IF-THEN statement is not true, the pro- gram moves on to the next line.

A Different Kind Of GET?

I can't seem to use GET statements in my Com-

1 2 COMPU T El's Gazette Fobruaryl98'l

modore 64 programs. I used the following line in a program on the Apple: 210 IF I = 15 THEN GET W$. This line causes the Apple to wait until a key is pressed. But the 64 docs not wait. What's going on?

Anthony Perry

Apple BASIC and Commodore BASIC are two dialects of the same programming language. There are a few com- mands and statements that seem to do the same thing, but don't. The GET statement is a good example.

On the Apple, GET ivill wait untd a key is pressed. On the 64, GET checks to see if a key is pressed, but it won't wait. If you don't type anything, the program continues.

If you want your 64 to ivait, use the following line:

10 GET G$: IF GS = " " THEN 10

Make sure you use tzvo double quotes, with no space befzveen them. The txoo adjacent quotes represent a "nuU" character, meaning that nothing was typed in. As you can see, if no keys ivere pressed, the line repeats over and over again. When you type something, the program continues.

When you learn one version of BASIC and then use a different brand of computer, if is a good idea to read the programming manual to find differences in the BASIC dialects. If you compare Apple and Coinmodore, you will find that most of the commands arc exactly the same. But there are a few that can fool you.

Mixing Uppercase And Lowercase Letters

How do you get capital letters on the same screen with small letters?

Shane Genis Capital (uppercase) letters and small (lowercase) letters are found in different modes on the VIC and 64. When you first turn on your computer, it is in uppercase/ graphics mode. Any letter you type will be in uppercase, and when you press SHIFT and a letter, you'll see the graphics character assigned to that key.

The simplest way to get into lowercase mode is to hold down (he Commodore key (on the bottom left of the keyboard) and press SHIFT at the same time. Now, all the letters you type are lowercase. To get capital letters in this mode, just hold down SHIFT and type a letter. To get back to uppercase/ graphics mode, just press the Commodore key and SHIFT again.

Although this is the simplest method, it won't work while a program is running. If you're writing a program in which you want to include a sxvitch to uppercase or lowercase mode, you must use these statements:

PRINT CHR$(14):REM SWITCHES TO UPPERCASE/

LOWERCASE PRINT CHR$(142):REM SWITCHES TO UPPERCASE/

GRAPHICS

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disable this mode-switching function. For example, if you're writing an educational game for small children, you wouldn't want a child to accidentally press the Commodore key and SHIFT and see all your graphics characters change to letters. To prevent this, use these statements in your program:

PRINT CHRS(8):REM DISABLES CHARACTER

SHIFT PRINT CHR$(9):REM ENABLES CHARACTER SHIFT

CHR$(8) disables the Commodore! SHIFT func- tion, but it also prevents any further use of PRINT CHR$m) and PRINT CHR$(U2) untU a CHR$(9) is PRINTcd. Many firogramnicrs make it a practice to in- clude a line at the beginning of their programs to disable character shifts — a good safeguarding technique.

A Computer Rounding Error

When I tell my VIC-20 to PRINT 158.41 -50. it an- swers 108.41. But when I tell it PRINT 158.41-150, it answers 8.40999997. What is the malfunction?

Peter Buyaki

Computers never make mistakes; only people do. Right? Wrong.

You are the victim of a rounding error. Tlic VlC-20 and most other computers use the binary system for mathematical calculations. While some numbers trans- late easily to binary, some do not. The same is true of decimal (the numbering system we're used to). The fraction Vs translates into 33 percent (after rounding off all those extra threes). And three times 33 percent comes to 99 percent. The result is off by 1 percent.

Assuming you were performing a financial calcu- lation, your result zuas off by only three niillionths of a penny, which should be accurate enough for most purposes.

You loill never be able to translate Vi into a perfect percentage (in decimal). And your VIC will never be exactly accurate when it uses certain fractions.

If you would like your program to round to the nearest penny, use this formula:

X = INT(X*100 + .5)/100

Or, if you zuatit to use this often in your program, you can define a function that does it for you. It will save some memory if you use it frequently .

DEFFNR(X> = INT{X'*100+.5)/100

If you DEFine the function at the beginning of a program, atn/time you want to round a nwnber, use FNR. For example, if the variable you want rounded is QP, you would use QP = FNR(QF).

The RND Function

I see the functions RND(O) and RND(l) in many programs. What is the difference between the two?

David Jennings

RND(O) loill generate a random number directly from

14 COMPUTEFs Gazette Februofyl?B4

the jiffy clock (an interval timer built into your com- puter). RND(l) will create a random number based on the last number generated by RND, If you use a negative number in parentheses, the computer zuill give you a predetermined (not really random) number.

Because comp7uters are designed to be logical, they cannot make up truly random numbers. When you use the RND (RaNDom) function, a number is generated by a mathematical formula which starts with one nu?nber and gives back another. The nuiTiber in parentheses is called the seed. The value and sign of the seed affect what kind of random number you get.

If the seed is a positive number, the value will not matter. A positive seed will make up a random number from the last value. Try typing in the following program line:

10 F0RX = 1T05:Y = RND(1):PRINTY:NEXT

When you type RUN, it will print five random numbers on the screen. If you RUN it again, you'll see a different set of random numbers.

Using a negative number as the seed will result in the same number every time. Add this line to the above program:

5S = RND(-1)

Now when you RUN the program, you'll still get a list of five numbers. But RUN it again and you'll see the same five numbers. Using a negative number pre- determines the series of random rtundKrs. Your com- puter uses a formula to create random numbers (which is xvhy they are sometimes called "pseudo-random").

A negative seed is sometimes handy when you are debugging a program or running a benchmark test. If you want random numbers, but always want them to appear in the sa}ne order, use a negative number the first time you use the RND function, and a positive seed in subsequent lines.

When the seed is zero, the computer uses the current value of the jiffy clock, which is updated 60 times every second. This gives you a way of randomly seeding the RND function.

Merging Two Programs

How can I merge two programs to use as a single program on my Commodore 64?

Khodadad Naimi

A program which will truly merge tu>o other programs must be quite sophisticated. It must collect all the lines front both programs in the proper order. It must also decide lohat to do if it finds the same line number in both programs. For an example of how this can he done with a VIC or 64 and disk drive, see the article on page 144 of the October 1983 issue o/ COMPUTE!, the gazette's sister magazine.

If you simply tvant to tack the lines from one pro- gram onto the end of another program (called ap- pending), that's a considerably simpler process. The follozving short program, from COMPUTEI's First Book of VIC, loill append programs, providing the

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ELECTRONIC ARTS

Home Software for the Commodore 64

UwV for fnir c^ihrr CHmnodpre M tHJo l»ltf AXIS ASSASSIN" WUR^tS.!'!■a^»J TKE TESSERACT STRATEGY" *t yooa friv^vrrt tturtpuitfr Huir. *of(»-,rtTftefiirt Mvi ai fWdtpanfnrtii »itn** thitMjj^LH theofurury

following restrictions are met:

• Nam' of the proi^rams may use line f lumbers 1-5.

• All lines in the program to be appended must have line numbers which are higher than the highest Hue number of the program iu memory.

1 A=PEEK(44)

2 PRINT"(CLR] {3 DOWN}LOADtl0 DOWN}

(4 LEFT1pOKE43,1:POKE44, ":A;"(H0ME]"

3 FOR I=631T0636:POKE I, 13 sNEXT: POKE 198, 6

4 IF PEEK(45)<2 THEN POKE 43, PEEK{45 )-2+2 55: POKE 44, PEEK( 46 ) -1 : END

5 POKE 43,PEEK(45)-2:POKE 44, PEEK{46) sEND

This program will work on both the VIC and 64 if you are using a Datassette. If you have a disk drive, make the following changes:

1 A=PEEK(44} :Q$=CHR$ (34) :R?=CHR$(141)

2 PRINT"(CLR) (3 D0WN)L0AD" fQ$;"PR0Gl";Q$,• ",8";R$; "{8 DOWN]POKE43, 1:P0KE44, "rAr"

(home}"

To use this program, type it in and SAVE it. When you want to append programs, first LOAD this pro- gram. Tape users sliould next insert the tape containing the first program to be LOADed and type RUN. Then insert the tapie containing the first program to be ap- pended a)ul RUN again. Continue until all programs have been appended, then delete lines 1-5. Disk users should change the program name in line 2 to that of the first mv'^ram to be LOADed. then RUN. Next, change

the program name in line 2 to that of the first program to be appended and RUN again. Repeat until all pro- grams have been appended, then delete lines 1-5.

The program works by changing the address for the beginning of BASIC to the address of the end of the program currently in nwmory (minus two bytes). The program tlien uses the dynamic keyboard technique to fool the computer into thinking Unit you typed in the LOAD and POKEs in line 2. These bring in the neio program, then restore the address for the start of BASIC to its original value. (Qf

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music

LET'S FACE IT Up till ncnv, music programs for your homo L'omputcr have all sounded, well, pretty lame. There were the ones that resembled little electronic music boxes, remem- ber? And then there were those that sounded like st) many burps.

Enter Music Construction Set. It's the first music program that really makes use of the power of dmt ma- chine you've got. If you're a serious student, this means you'll be able to work with an intricacy and range of sound quality you've never heard be- fore on a computer, And if you know nothing about music, you'll find some- thing even more important. Namely, that this diing is simple enough to be a lot of fun.

Take a good look at this screen because it, you, and a joystick are the whole story here.

That's you at the right end of the staff of notes — the little hand. Move the joysrick, and you move the hand. Use it to carry notes up to the staff. Lay in rests,signatures, clefs, then point

to the little piano in the lower right and listen, because you'll hear the whole thing played back.

Move diose litdc scales in the mid- dle up and down to var>' the music's speed, sound ciuality, and volume. Use

the scissors to cut out whole measures, then use the glue pot to paste them in somewhere else. Got a printer? Great. Print the score out and show it off to your friends.

But what if you're not up to writing your own stuff yet? No problem. There are twelve pieces of music al- ready in here, from rock 'n roll to b a rot] ue. They're fun to listen to, and eveii more fun to change. (Apologies to Mozart.)

The point is, the possibilities are endless. But if you're still skeptical, visit your nearest Electronic Arts dealer and do the one thing f^uaranteed to send you home with a Music Con- struction Set in tow.

Boot one up. Point to the piano. And listen.

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SIMPLE ANSWERS TO COMMON QUESTIONS

TOM R.HALFHILL, EDITOR

Each month, coMPUTEl's GAZETTE will tackle some quest io>ts cointtionly asked hy ncxo VlC-20/Coinmodore 64 users and by people shopping for their first home computer.

^Ktm I've seen advertisements for "printer buf- fers" and have read many references to "cassette buffers," "keyboard buffers," "input/output buffers," and so on. Exactly what is a buffer?

£%m Generally speaking, a buffer is a reserved area of memory v^rhich holds information until it is ready to be processed.

Buffers are most often employed in situations where the computer is too fast for its peripheral devices (such as printers, disk drives, tape drives, etc.). The speed disparity between computers and their peripherals has shackled computers ever since they were invented. The problem is that computers, electronic devices which operate almost at the speed of light, can easily outrun mechanical devices. No machine wliich depends on pulleys, rollers, gears, levers, and electric motors can keep up with a computer.

Let's look at printers, for example. A typical home computer hooked up to a printer is capable of sending many thousands of characters per sec- ond to the printer. But not many home computer printers can print more than 100 or 200 cliaracters per second. Like a harried factory worker stationed on a lightning-fast assembly line, the printer can't keep up. If nothing were done to remedy the situ- ation, maybe one of eveiy ten or 100 characters would be printed. The rest would be lost in the shuffle.

One solution, in effect, is to slow down the computer so it doesn't send characters faster than the printer can take them. Although this restores the balance, it also drastically reduces the com- puter system's efficiency. When printing out a long program listing or text file, you have to wait until the printer is finished before the computer is

30 COMPUTEFs Gazette February 1984

available for another task.

A better solution is to set aside (or add) some memory for a buffer. Let's say we reserve 8K — enough to hold 8000 characters. Now, whenever we want to print a file, the computer sends the characters to the buffer at top speed until tlie buffer is filled. The buffer then sends the characters to the printer at whatever speed the printer can handle. As long as the file we're printing is not larger than the buffer, the computer is freed for other work while the buffer and printer chug away at their own pace. The computer's time (and your time) is not wasted.

Printer buffers are a commonly available ac- cessory for most computers. (Some printers have built-in buffers.) But buffers aren't always out- board accessories. Computers, by necessity, have several internal buffers. One is the keyboard buf- fer. This is a very small buffer (usually one to ten bytes) which holds characters typed on the key- board. To keep very fast touch- typists from out- running the keyboard, the keyboard buffer stores keystrokes and then passes them along to the computer for processing. (On the VlC-20 and Commodore 64, the keyboard buffer is normally ten bytes long and is found at memory addresses 631 to 640.)

Similarly, a cassette buffer temporarily stores data on its way to or from the tape drive. There are also buffers for disk drive input/output.

Sometimes programmers — especially ma- chine language programmers — -take advantage of buffer memory space for their own purposes. On Commodore computers, for instance, the cassette buffer is a popular place to store short machine language routines. If the program is not using cassette input/output, the cassette buffer is idle and is a reasonably safe place to hide the machine language. The cassette buffer on the VIC and 64 is 192 bytes long, found at memory addresses 828 to 1019.

QCb What do the terms "coldstart" and "warmstart" mean?

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MusiCalc

ne&e^lHbisieSfstm

MAKE MUSIC PLAY On Your Commodore 64"

Put the MusiCak ' diskette into your Commodore 64. Sit down. And brace yourself.

You're about to discover an entirely new way to make music. With Musi- Calc, the creative music system that makes music play Almost instantly, the whole family will be able to create and perform all kinds of music. From rock 'n roll to tcchnopop, from classical to country western.

MusiCalc makes music more fun, more rewarding and easier than it's ever been before.

NOTEWORTHY SOFTWARE

MusiCalc softivaro turns your Commodore 64 computer with disk drive into a sophisticated musical instrument. And it turns you into a composer, performer and conductor

MusiCalc I's Synthesizer & Sequen- cer is the heart of the system. Witli it you can use your computer key- board to program the tempo, key

and style of music you want, and also to play your favorite tune. The com- puter screen will show you what the music's doing as you play and how to control it.

Start by selecting one of MusiCalc's preset scores. Try combining that with a preset sound you like. Choose the scale you want to play in— anything from jazz to Japanese.

Presto! You've got music.

Exercise your musical creativity by putting the three voices together any way you want, and playing whichever parts you'd like. Make changes and add special flourishes to create your own compositions.

Even a musical novice will sound good right away. And the greater your musical talent, the more challenging and exciting MusiCalc becomes.

BACH TO BASICS Although simple to leam, MusiCalc was designed to meet the needs of pro- fessional musicians.

In fact, it delivers the quality and capabilities professionals have spent thousands of dollars for— up until now Once you have the Commtxlorc 64 computer and disk drive, you can get started for under SIOO t\ith the Musi- Calc 1 Synthesizer & Sequencer. This is a standalone software program you'll never outgrow. And with the variety of other MusiCalc products currently available, plus the many more itenis Waveform will be introducmg in the months ahead, you can expand your music system along with your interest and ability,

THE MUSICALC SYSTEM MusiCalc includes a full line of soft- ware that brings great music ^ close as the keypad of your Commodore 64. MUSICALC 1, Synthesizer & Sequencer Turns the Commodore 64 into a sophisticated musical instru- ment—a three- voice synthesizer and fully- interactive step i«bm^__im

sequencer. Play along with a song or write your own. Develop your own instru- ment sounds. And record the music you create.

tlh..

v^i..

MUSICALC 2, ScoreWriter • Works with the Synthesizer & Sequencer to change your music.il improvisations into musical notation. With the addi- tion of an optional graphics printer you can , turn your

^

ovwi original compositions into sheet music. Requires MusiCalc I to operate, MUSICALC 3, Keyboard Maker ' 'Enables you to create your own custom musical keyboards. Comes with over 30 preset keyboard scales from around the world— everything from classical to rock. Requires MusiCalc 1 to operate. MUSICALC TEMPLATE 1, African and Latin Rhythms Add this to the MusiCalc 1 system and it provides additional musical scores and patches you can play along with or use to develop your ovm compositions. Requires MusiCalc 1 to operate.

MUSICALC TEMPLATE 2, New Wave and Rock Works like Template 1 and features the latest Technopop scores and sounds. Requires MusiCalc 1 to operate,

MUSICALC

PROFESSIONAL SYSTEM The MusiCalc S>Tithesizer & Sequencer, ScoreWriter, and Keyboard Maker, plus the two Templates, in one cost-saving package. HIT DISKS Recordings to play on your computer. Original Technopop com- positions, current hits and old standards performed by the Waveform Band. Ask your dealer about current releases.

COLORTONE KEYBOARD AND MUSICALC 4 A totally new concept in keyboards, ideal for everyone from novice to professional. A professional quality keyboard that's remarkably easy to learn how to use. Tlie keyboard comes with special software that allows it to work with MusiCalc 1 and 2, enabling you to play music on the keyboard and record it on disk to play back or print out later. Add MusiCalc 4 and play any scale in any key, for even greater musical capability. Available soon.

DEMO DISK An entertaining and infor- mative demonstration of the capabilities, features and uses of the entire MusiCalc System. Also available in tape cassette.

MAKE MUSIC PLAY

MusiCalc will make music come dive for the entire family. It's a fun and educational way to introduce your children to music and computers. And no matter what your background, you'll find yourself playing and understanding music in an exciting new way.

Ask your computer or music dealer about MusiCalc. Or send in the attached coupon and $5 for the MusiCalc Demo Disk or cassette. Discover MusiCalc, the creative music system.

MUSIC PRODUCTS DIVISION

MAKING MUSIC PLAY

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M%m They refer to two different ways of resetting a computer. Resets are generally necessary for programmers; sometimes a programming mistake {particularly in machine language) "locks up" the computer. That is, the computer no longer re- sponds to commands typed on the keyboard. It just sits there as if paralyzed. At other times, a programming error scrambles a program or its data so hopelessly that the only way out is to reset the whole computer.

A coldstart is the most drastic type of reset. The ultimate coldstart is to switch off the com- puter's power and then switch it on again ("start it cold"). Of course, since Random Access Memory (RAM) requires constant power to hold its infor- mation, this kind of coldstart completely wipes out the program and all its data — perhaps irre- trievably, if a copy was not saved on tape or disk.

Sometimes a less drastic type of coldstart is possible. For example, if you enter SYS 64802 on the VIC or SYS 64738 on the 64, the computer seems to perform a power-off/on reset. Default screen colors and internal pointers are restored, the initial power-up screen appears, and any BASIC program present before the reset seems to be gone. However, the program is still in memory and can be recovered with a utility such as "VlC/64 Program Lifesaver" (COMPUTEI's GAZETTE, November 1983). Another way to simulate a cold- start is to short together certain pins on the VIC or 64 user port (see "Horizons: 64," December 1983). Some plug-in memory expanders and motherboards use a similar technique to add a real reset button.

A warmstart is a less destructive type of reset. It resets the computer without erasing valuable programs or data. To prevent accidental resets, the VIC and 64 require a two-keystroke sequence: hold down RUN/STOP and slap RESTORE (merely pressing RESTORE doesn't work; it takes a some- what sharp — but not savage — slap). This clears the screen, restores original colors and some in- ternal pointers, and preserves your program, &

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A Mutated Wonderwhisk whisks by. ^i^^ Keep bouncing Joe to original

The SpinningTbp almost topples him! ^HnH music on realistic 3 -dimensional

Close. But Pogo Joe ■'^[[J^B cylinders. All the characters in

bounces back. Bouncing pjpHthis rollicking j

from cylinder to cylin- E B= H game are

I der, screen to screen, also 3-dimensional and

I Pogo Joe racks up point fully animated.The

after point graphics almost jump

You guide him from off the screen, leaving

cylinder to cylinder, changing the color on the arcades behind. top of each. Change the top of each cylinder Whafs ahead with Pogojoe"'is $10,000.

on a screen, then you're fPj^^HHj^^^^ Simply tell us what magic word appears on to the next. HVfSHHI Z""^- — ^T^ after Pogo Joe^ tenth

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you complete, the Lj^ jJS /^aB|^^ai^^)l\ is drawn from

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they attack. IJii^U^^^ ^^^^9S^^^^ $10,000!

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button! Jump two cylin-B^^^^HHl ^proCfAHAmM necessary You'll ders to safety Hop into ^^^^^B&^H WIJ!x3JiiiijOi| ^^ f^nd entry fonns at a transport tube, and ^^^^S^^^^a ^ny store that sells Screenplay'" games.

then whoosh! Pogo Joe ^P3*^^^*QPIW But if you don't win you can't lose Pogo appears across me "^

screea Jump on an ^^^Hi^^^V for joy no matter what IjS?"^.

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'Bits And Bytes"

PBS's New Computer Series

Kafhy Yakal, Editorial Assistant

Once you get started with personal computers, there are many ways you can learn about them. Schools offer computer literacy courses. Books and magazines publish information. User groups offer first-hand help with fellow hob- byists. Now television is starting to show some interest in computer education. Here's a look at a Public Broadcasting System show that is receiving a veiy favorable response: "Bits and Bytes."

Frances Seidenberg wanted to learn about computers. Knowing how to use one, she thought, would be helpful in her job as a freelance editor for a Toronto publishing company. She did have access to personal com- puters at work, and was learning a lot by editing books on educational software, but she felt that more personalized instruction was necessary. So she and her husband enrolled in "Bits and Bytes," a 12-week introduction to microcomputers that was being offered through TV Ontario, a public television station.

"It was absolutely perfect," says Seidenberg. "There was something in every program that 1 found useful."

"Bits and Bytes," just completing its second run on Canadian stations, is scheduled to be in-

26 COMPUTEI's Gazelle February 1984

troduced to U.S. audiences in January 1984, under a different name: "Academy On Computers." The original course material, written by Jim But- terficld, has been substantially updated for its U.S. debut.

Initially, the show will originate from ten stations: KCET (Los Angeles); KPBS (San Diego); the Kentucky Educational Network; the Nebraska Educational Television Network; WNED (Buffalo); WNET (New York City); WXXI (Rochester, New York); WMHT (Schenectady, New York); WGTE {Toledo, Ohio); and WHA-TV (Madison, Wiscon- sin). A second run is already being planned be- ginning in mid-Apdl, with several more stations participating. (Interested readers should contact their local PBS stations for more information.)

Of course, anyone within range of these PBS stations can watch the show for free. But those who sign up for the course and pay the registration fee of about S70 (this figure may be set by indi- vidual stations) will receive special courseware. The courseware includes text written to accom- pany the show, individual advice and instruction via periodic quizzes and evaluation sheets, a newsletter, and access to a special hotline staffed by local computer experts.

The creators of "Academy On Computers" say they designed the series for people who are interested in computers but who are bewildered by high-tech jargon, fuzzy computer manuals,

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Hosts Luha Goy and Billij Van do the teaching and detnonstratitig in the tele- vision series "Bits and Bi/tes," one amipaiicnt of the ACADEMY ON COMPUTERS, a comprehensive educational package which provides computer training via television. The tioelve-part television series premieres over ten public television stations the week of \amtary 22, 1984.

and the flood of available hardware and software. During the course, viewers will be briefed on basic computer technology and will be introduced to sources of further information, such as software, books, magazines, and organizations. They w^ill learn about the tj^pes of computer programs in use today, how to evaluate and select software, how to operate a personal computer, and even how to develop one or more simple computer programs. "The handbooks and newsletters that accom- panied the show were very helpful," says Frances Seidenborg. "But perhaps more important than that was the resources they pointed me to, like publications and user groups. I was able to visit computer stores while shopping for a micro and know what I was talking about."

L he Montreal Gazette described the series as "the most intelligent, useful, and timely educational program on television today." Each half-hour show uses a variety of teaching techniques. Prac- tice portions are interspersed with theory. There are explanations with computer and cell anima- tion, interviews with experts, and visits to places such as Silicon Valley in California and a computer time-sharing service.

"Everything was very understandable," says Seidenberg. "When they came across a topic that was difficult to understand, they had little ani- mated characters that simplified the explanation. It was informative without being too easy."

Canadian actors Luba Gt>y and Billy Van host the show. "She acted as the teacher, he the

30 COMPUWs Gazelle Februor/ 1 994

Student," says Seidenberg. "He started out as the audience did, knowing nothing, and learned along with the audience. It was very effective."

Several factors make "Aca- demy On Computers" unique. First, it allows viewers to set their own learning paces at home, unlike traditional TV courses which require enrollment through a local school. Second, it is a participative learning ex- perience, thanks to the computer- managed evaluation system, consulting experts, and tele- phone hotHne. Third, the show has the potential to reach the broadest audience of any com- puter instruction course ever taught: 13,000 people signed up for the first run in Canada, and many more are expected to en- roll for the U.S. premiere.

It's not necessary to own a computer to benefit from the series. Seidenberg didn't have one, "We had planned to purchase an Apple He, but didn't get it until after the course was over," she says think the course was still as effective."

George Rose, a Toronto resident who signed up for "Bits & Bytes," also didn't have a personal computer when he enrolled in the course. He still doesn't have one. "I think the course is very ben- eficial to someone who is interested in buying a computer," he says. "I'm still watching the mar- ketplace and asking myself, 'What am I getting from my dollar?'."

Rose, the marketing director for a Toronto manufacturing company, says that years of working with business computers sparked his interest in home computers. Though he was very familiar with the workings of larger computers, he found "Bits and Bytes" a challenge, "The course material was very good, and the presenta- tion was quite clear," he says. "But home com- puters are a lot different than the ones 1 was used to. 1 had to really think about the questions before 1 could come up with an answer."

The show does not focus on one specific brand of hardware or software, though the low end of the market is well represented by companies such as Radio Shack, Apple, and Commodore, Each program covers general information that applies to most computers, though specific models are used for demonstration purposes.

1

icre are examples of topics covered in some of the installments:

FIRST, THE GQjU)

ew Crames.

First Star Has 4

Fernando Herrera, the designer of ASIJfO Cfi/iS£' (1984 Superior graphics, real-time animations'", multiple screens.

Science Fiction / Fantasy Computer Game of the Year " ) and intermissions, arcade-quaUty sound, innovative gaming,

our design team again define "State of the Art." challenge and excitement- we deliver It alll

THE BAD MEWS? You cant play them all at once.

Bomo!

Deslgnei by Alex Leavens ■ & Shlrlej A RusssU JM Awn VCS 2600

BRISTLES

AStirruii fsvsr Ihe PalntBr ^^ Designed by ;^^!iM.j^,4«!M,

C Atari Home Computers Commodore by Adam flellln

FLIP and FLOP PiUffIG BUTTON

,^ Designed by Jim Nan gin o *"*' Atari Home Computera ^ Commodoffl by Paul Kanevsky

MTHS-80 Color Computsr by Paul KaneTsky

^jj Commodorfl Compuwra

'Electronic Oames Magazinfi 1984 Game Of Ths Year Award

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Program 1; Getting Started

• Explanation of basic computer terms: bits, bytes, chips, disks, CPU, etc.

• How to load disks and cassettes.

• A Hewlett-Packard representative takes a disk and disk drive apart and explains how they function.

• A discussion of artificial intelligence. Program 3: How Programs Work

•An introduction to different computer languages.

• How to set up simple computer programs using GOTO and IF-THEN.

• An animated sequence explains the interac- tion between the CPU, RAM, and ROM, and what happens in the computer during input/ output.

• A visit to Computertown USA in Menio Park, California, a grassroots computer liter- acy organization.

Program 5: Communication Between Computers

• How modems work.

• How a personal computer can be linked through a modem to other micro-, mini-, and mainframe computers for sharing information.

• How to use a modem to contact bulletin boards systems (BBS) and data bases.

• A visit to The Source in McLean, Virginia, to show how an information service works.

Program 8; Simulations and Games

• Explanation of the concept of computer sim- ulations, and how paddles and joysticks work.

• A survey of popular computer games.

• The difference between analog and digital.

• A visit with an Atari game designer who tells how simulations and games are being used in schools.

Program 10: "Computer Music"

• How to turn a computer keyboard into a musical keyboard.

• How to use music and voice synthesizers.

• A visit to Scarborough High School, the University of Toronto, and York University to show how music is taught with computers and synthesizers.

Program 11: Computers At Work

• How to use a word processor and other text-editing systems.

• How to use electronic spreadsheets such as VisiCalc.

• How printers and plotters work.

• A visit to an Ontario school which uses word processing in the classroom. Q

VICTORY SOFTWARE

Programs lor the VIC-20 ond the COMMODORE 64 All gomes available on TAPE ot DISK and are packed lull of MACHINE CODE.

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METAMOBPHOSIS

Vou stumbled Into Hie resr o( the Cyglorx and Una youisell lighMng off lODol tanks guarding ttie Cyglorx eggs. You tfilnit you have evaryttiing under control and then trie eggs start fiotching. Commodore 64 version leotures 4 dllleront screens. Available lor COMMODORE 64 ond VIC-20. Played with JOYSTICK.

A CREATOR'S REVMOE

^ The nfftntnr n^.iemhffiri n mnsiilv

The creotor assembled a massive army of robots and insects to toke revenge on the earth. Destroy Insects, get treosures. and get the neutron bomb diactivotor Battle robots and destroy the neutron bomb belore it annihilates your city. Miss ond you musi face Ihe mutants, Feotures 4 different screens. Avollable for COMMODORE 64. Ployed wilti JOYSTICK.

LAETBIBTH OF THE CREATOR

Journey Into the most complex ond dangerous lortrass ever build by tfie creator. You will encounter deodiy robots, skulls, lakes, avolonches, false creators, and o creature who roams 256 rooms relentlessly pursuing you. Available (or COMMODOHE 64. Played v^llh JOYSTICK.

^^^^An adventure in the Old West. Journey bock ^r witti us into the days ol Jessie James and Billy the Kid where the only form of Justice was a looded revolver and a hangmon's noose In this lull-length te>tt odventure, you ploy the role ol Bounty Hunter, bottling against ruthless outlaws, hostile Indians, wild animals and Ihe elements of the wilderness with oniy your wits and your six gun. Averoge solving time: 20- 30 hours It you love adventures, this one is o reai freot.

Avoiiobie for COMMODORE 64 or the VtC-20 (with aK or 16K exponder). Ployed with KEYBOARD,

^^^^ Climb lodders, avoid ihe borrels the croiy ^^ape Is rolling at you. and rescue Ihe dormsel Commodore 64 version features 4 dltterent screensl AvollOble lor COMMODORE <S4. Ployed wllh JOYSTICK or K£YBOAHD.

^^^^ Eorth's surface Is threatened by collapse from ^^o strange group of creotures who bore out Ihe earth's crust lo make their dens. Vouf objective is lo enter the creatures hobilat ond spin the Invaders to death Available ror COMMOEXDRE 64. Played with JOYSTICK.

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software specially designed for the Commodore VIC 20.

Now \'0\i cnn use your Commod VIC 20 to pfrform ;ill ihu fiikulatiiins on your t^iiiailiiin Tl KcntTni tiix form, TiixtMnk iiiiiiks you easily through fVLTy i)S[-n:fi of the form witii friLrildiy priimprs and a comprehensive jnsiruction maTiu:iL This nt'w sofiwnri." is available on cassette Ka\\- nnJ will run on the standard l.'ik memorv in your Commodore VIC! 20 home computer.*

Ttapiiclt lets you tiiekle your income tax form at your OWEi pace. A convenient save-anj-restore function lets yau record ;ind review historical results. Proftssional editing features assure easy and accurate data entry. Taxfmck puts the jTower of tad modellinj! and I'lannin)' for subsetiueiil years in your hands, today.

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Many happy returns

IVcaiiSk' yoti can caleul:ire and preview nmre t.ix scenaritJS u'tth Tax!>iit:k than yoti'd have the patience or the time to do manually, this software can help you save tax dollars. Custom-tailored to the Canadian Tl general form. TtuJiUt'k H ill be upilaieil every year to reflect changes in the government's income tax rejjulaiions, Innovative proKtiim design allows lis to update TiIxjhkIi within days of the new Tl 's availahitity.

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The Inner Woild Of Computers

Part 4: The Inside Story

Tom Prendergast

In the first three installments, we discovered the on-of f switches in the computer, as well as how to control logic and store information by turning switches on or off. This month's in- stallment explains binary arithmetic — the numbering system your computer understands.

When Snow White's seven dwarfs went whistling off to work, it wasn't to do computing — because seven's not a power of two. But if she'd been a liberated woman and gone to work with them, it would've made eight. Eight is a power of two, and the powers of two are what give computers their computing power.

Decimal (base 10) has been our way of writing and thinking about numbers for thousands of years, and as long as humans have ten fingers and toes, we'll be using decimal for thousands of years more.

Computers, though, are binary. Everything you type into a computer ends up turning tiny micros witches ON or OFF: binary.

It doesn't make any difference whether you think of binary as sequences of I's and O's, as heads or tails, as hot or cold, even/odd, yes/no — the computer doesn't know, or care. So if com- puters think^ — and you can get into a big argument on this — they think in binary terms: on/off, yes/no.

34 COMPUT£i's Gaielte February 1984

But people don't think in binary, U's always "yes, maybe," or "no, but.,.," That's OK, though. Who wants a computer that gives you a lot of ifs and maybes when all you want is a simple answer?

1 he powers of two, if you remember from our previous articles, are multiples of two: 1, 2, 4, 8, 16, 32, 64, 128... and so on to infinity, which is one of those mythical places like ELFdom that you can never quite get to.

SNOBYTEAND7=8

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Here are the powers of a byte in "exponential notation":

t7 tyb T.5 -^4 1^3 rjZ >i1 oO

The little, raised numbers (the exponents) tell you how many times the base {in this ease, 2) is multiplied to give you the power of that position. Starting from the right, 2^' is two multiplied zero times (in other words, it's not multiplied at all). Next is 2', "two to the first power": two multiplied once, or 2*1. 2~ is two multiplied twice, 2*2, two squared; and 2-^ is 2*2*2, and so on. Home com- puters, though, don't have the little exponent numbers, so you have to use the up-arrow ( I ) key above RETURN on the VIC and 64 keyboard.

If you want to find out what 2 to any power is, ask your trusty VIC or 64. (I always use a ques- tion mark — the abbreviation for PRINT — when I'm asking my computer a question.) Try this:

?2 I 7

Did you get 128 for an answer? Now, try 2":

?2 to

Surprised? You'd think that the zero power would be a 0, wouldn't you? The zero power of any base — binary, Irinary, quartal, octal, decimal, hexadecimal — is always one, or "unity." Try the zero power in decimal (base 10):

?ioI 0

Still got a 1, right? Now ask for 10 to the first power:

?10 Ii

Did you get 10? Switch over to hex (base 16):

?16tl

You should get 16, Switch back to binary (base 2):

72 tl

and you get 2! The first power of any base is always the base itself — 2 for binary, 8 for octal, 10 for decimal, 16 for hexadecimal, and so on.

H.

lexadecimal is a very close relation of binary. You might even call her Auntie Hex, because 16 is a power of two (2''), and as we know from previous articles in this series, hex is shorthand for binary. That is, every four-bit segment of binary (a nybble) can be directly translated into hex:

Hex:$ 9 0 0 F

Binary: 1001 0000 0000 1111

It also works the other way around, as you can see in the above example; Every hex digit can be directly translated into four binary digits.

This can get a little confusing, so let's look at a prggram that illustrates the similarities and the differences between binary and hex:

3A COMPUWs Gazette Fobruory 1 984

10 POWER=0 :reiii 91

20 PRINT" 2t"P0"=" 2tPOWER :rem 0

30 PRINT"16T"PO"="16tPOWER :rein 107

40 P0WER=P0WER+1 :rem 23

50 GET G$!lF G$=""THEN 50 :rem 249

60 PRINT: IF P0WER<=4 THEN 20 : rem 135

When you type RUN and RETURN, the zero power of 2 (binary) and 16 (hex) both appear. Press the space bar, or any key, to get the next power of 2 and 16. If you want to go off into never- never land — close to infinity — or at least until you get an ?ILLEGAL QUANTITY ERROR, change line 60 to:

60PRINT:GOTO20

Neither hex nor binary, though, can be di- rectly translated into or from decimal. How do you figure out the decimal?

It's tough enough figuring out the binary for nybbles and bytes, but what about those really big numbers?

Now for the good news: You need binary only for manipulating DATA — when you're AND- ing and ORing and doing those other fancy tricks we touched on earlier in our series. And since DATA is never bigger than a byte, that means you'll never have to know binary beyond 255 (llllllll).

This is because the VIC and 64 (and Apples and Ataris) are 8-bit computers, and llllllll — a full byte — is the limit of "on" bits you can pack or POKE into a memorj' cell. Each memory cell is also known as a itieiiion/ hicntioii or a memonj ad- dress— a place where a byte is stored.

\^f ten times, though, the computer needs to deal with numbers bigger than a byte — greater than 255.

But how do you pack 16 bits into 8 bits in an 8-bit computer? You don't. The computer hitches two bytes together to form a two-byte address. With 16 bits to play with, you can have an address as high as 65535 (1111111111111111 in binary). There's a "zero" address, too, but since addresses are always two bytes long, its binary form is all zeros: 0000000000000000 ($0000 in hex).

Of course, the computer uses binary for ad- dresses, too, but when you're programming in BASIC, your computer handles that automatically.

Suppose, though, that you're looking at a memory map showing where certain color or ,sound operations are located, and you'd like to POKE different values into these locations (ad- dresses). Sometimes the addresses are given only in hex.

You could rush out and buy one of those calculators that translate decimal to hex, or hex to decimal, oven octal. They cost $20 to $100. Another way is to multiply each hex digit by its hexadecimal

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power, add them all together, and — if you haven't made any mistakes — you've got your decimal. Gulp!

If you're going to do many of these conver- sions, or if you're as bad at figures as I am, it'll be worth your while to type in the utility programs which let you input any hex or decimal number and get the conversion. (See Programs 2 and 3 at the end of the article.) They're not as much fun as "Binary Castle" a few months ago, but based on the same idea.

The Commodore 64 has 65536 byte-sized memory cells — 0 to 65535 — which you can ad- dress. Approximately 27,000 of these are ROM (Read Only Memory). You can address any mem- ory cell, RAM (Random Access Memory) or ROM, or PEEK to find out what value is stored there, but you can only POKE a new value into a RAM cell. The big difference — and it's huge — between the 64 and the VIC is the amount of RAM memory cells. You can still address 65536 memory cells on a VIC, but that doesn't mean there's anyone at that address to receive it: it's like mailing a letter to a vacant lot.

M hink of your computer as a giant warehouse — shrunk down to ELF size— where they store Wliat- sits. Whatsits have all sorts of uses, some that haven't even been thought of yet — which is why they're called Whatsits, Like automobiles, What- sits come in all shapes and sizes, but, unlike auto- mobiles, they never wear out. Another thing, if you don't like the way they run, you can take them apart and reassemble them because all the parts of a Whatsit are interchangeable— like pro- grams. In fact, Whatsits are program bytes.

Now imagine an army of ELFS grabbing the Whatsits off the conveyer belt (as you type in your program), climbing up ladders, and storing the Whatsits on the shelves so they'll be ready when the program is run.

The Whatsits for PRINT and GOTO and other operations go on the bottom shelves where they'll be handiest, and those for the variables and strings are stored up top.

This is OK if you have enough shelves. But if you have only a few thousand shelves, like an unexpanded VIC, the variables and strings begin to fall down from the top and meet the program parts coming up. What do you do then? You just can't pile the new parts coming in all over the place. How would you ever find them when the program needed them? So the ELF in charge of storing things blows the panic whistle and ? OUT OF MEMORY ERROR flashes on your screen. No more storage space, no program.

There's another thing that can go wrong, too. (Isn't there always?) Even if you have enough storage space, the data bytes have to be in the

38 COMPUTE'S Gazette Februoryl984

right place (address) on the shelves. As the ELFS say: "Without the right address, a byte is a blyte."

For instance, if you want to turn the VIC screen black with white letters at a certain point in your program, the data byte "8" has to be in address 36879 when the program calls for it.

But let's say your program is just the right size for the amount of memory. You might even have a few empty shelves for data bytes created later on in the program. Things are running as smooth as silk and all you can hear are little clicks of ELF talk (ELFin) as your program starts its run. But ELFin has a lot of uses aside from running the system inside the computer. There's a technique called "bit indexing," which 1 plan to have ready for demonstration next month. This allows for quick and easy handling of thousands of data items, without using thousands and thousands of bytes of memory. This means you can run a huge "professional" data bank system on an unex- panded VIC!

In the meantime, if you have trouble figuring out binary above Till (15), use Program 5,

If you're like me, though, you've always got a program running when you need a quick con- version. If you don't have another computer to run one of the conversion programs at the end of the article, you'll have to do it the old-fashioned way, with pencil and paper.

Fear not, though. There's an easy, if some- what slow, way of converting decimal to binary. The trick is to keep dividing by 2.

A o start off, we jot down a 1 if the decimal number we're converting is an odd number, or a 0 if the decimal is even. Then we divide the number by two — ignoring any remainder — and put down a 1 if the result is odd, or a zero if it's even. We keep dividing each result by two until the division results in 1.

To convert 16 to binary, for instance, we start by putting down a zero because 16 is an even number:

16 0

Sixteen divided by two is eight — another even number — so we jot down anotlier zero. Eight divided by two is four, still even and another zero. Two divided by two is one, an odd number, fi- nally, and we jot down a one. We can't divide one, so we write our four zeros and the one down in a row starting from the right, and see that 16 is 10000 in binary. The complete operation should look like this:

16 (even) =	0
Vz = 8	0
«/2 = 4	0
Vi=2	0
% = 1	1
16 =	lOQOO

Zu-i^:^^if^jx'iA ;-ir,;^4M_.

You'll never make Grand Prix champion just driving in circles.

You've got to stop sometime. The question is when. Right now you're in the lead. But the faster you go, the more gas you consume. And the quicker your tires wear down.

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We add three leading zeros to make the full byte of eight bits and get:

binary 16 = 00010000 hex 16 = $1 0

You'll get to be an expert so fast you'll be able to do this in your head and not have to write anything down. And since you can convert each binary nybble to hex, it's a faster way of converting decimal to hex than dividing by a lot of 16s. More trustworthy, too.

Let's do another decimal-to-binary — with a number that's bigger and not a "power of two" like 16 — so you'll get the hang of it. Let's convert 171 to binary. Since 171 is odd, we jot down a 1:

171 1

Dividing 171 by two gives us 85 (forgetting the remainder), and this is odd .so we jot down another one. 85 divided by two is 42 — an even number — so we jot down a zero. 42 divided by two is 21 — odd — so we jot down a one; 21 divided by two is ten — even — so we jot down a zero; 10 divided by two is five — odd — so we jot down a one; five divided by two is two — even — so that's a zero; and two divided by two is one — odd — and that's a one.

We don't need leading zeros this time be- cause we have a ful! byte, so our binary looks like

this:

binary 171 =10101011 hexl71 = $A B

Powers Of. 2 And 16

5 REM POWERS OF 2 AND 16 : rem 250

9 PRINTGHR$ ( 147) ;CHR5( 18) ; "TOUCH SPACEBAR " :rem 237

PRINTCHR${ia);" TO C0NTINUEE2 SPACES]" :POWER=0 srem 100

PRINT" 2 t"P0"="2tP0 !rem 18

PRINT"16 T"P0"="I6tP0 :rem 125 P0=P0+1 ;rem 59

GET G5:IFG$=""THEN50 : rem 249

PRINT: IF P0<=4 THEN 20 : rem 153 PRINT" 65535 IS THE HIGHEST" :rem 201 PRINT" {4 SPACES} ADDRESS ON THE"

:rem 189 PRINT" {6 spaces] VIC OR 64"

10

20 30 40 50 60 70 80

90

Hex To Decimal Conversion

10 REM HEX TO DECIMAL

20 PRINT! PRINT"HEX NUMBER:"

30 INPUT H?

40 L=LEN{H$) :XP=L-1

;rem 39

:rem 188

:rem 226

:rem 95

L=LEN{H$) :XP=L-1:F0RI=1T0L:DM$=MID5(H5

,1,1) :retn 210

50 IPDM$<="9"THEN DM$=STR$ {VAL(MID5 (H?, I ,

1)}) :rem 239

60 IFDM?=>"A"THEN DM$=STR$ ( ASC( DM$ ) -55 )

;rem 173

70 D=D+(VAL{DM?) )*16TXP:XP=XP-1 : rem 7 7

80 NEXT: PRINT: PRINT" {3 SPACES}?"H?" ="D"D

ECIMAL" : PRINT: RUN :rem 247

Hex To DecimaiyDeclmal To Hex

10 REM HEX TO DECIMAL trem 188

20 PRINT: PRINT"HEX NUMBER:" !rem 226

42 COMPUTEI's Gazelle Fobfuory19a4

30 INPUT H$ :rem 95

40 L=LEN(H$) :XP=L-1:FORI=1TOLjDM$=MID?{H$

,1, I) srem 210

50 IFDM$<="9"THEN DM$=STR${VAL(MID$(H$,I,

I) ) ) srem 239

60 IFDM$=>"A"THEN DM$=STR$(ASC(DM$)-55)

:rem 173 70 D=D+{VAL(DH$) )*16tXP:XP=XP-l :rem 77 80 NEXT! PRINT: PRINT" {3 SPACES}$"H?" ="D"D

ECIMA.L" sPRINT :rem 200

90 PRINTCHR$(18); "[2 SPACES }TYPE ' D' FOR

{2 SPACES} ":PRINTCHR$( 18) "DECIMAL TO H

EX" srem 40

100 GET G$:IFG$=""THEN 100 srem 81

110 IF G$<>"D"THENRUN srem 178

111 REM***DECIMAL TO HEX*** srem 234

112 REM* {2 SPACES} BY R.MANSFIELD

{2 spaces]* srem 122

113 REM******************** srem 193 120 HE?="0123456789ABCDEF":INPUTDsDE=D

srem 185 130 H5="":F0R M=3TO0STEP-1 ;N%=DE/( 16TM) : D E=DE-NS*16TMtH$=H$+MID$(HE$,N%+l,l)

: rem 8 140 NEXT:PRINTD"= $"H?" HEX": RUN srem 72

Any Base To Decimal Conversion

10 REM ANY BASE TO DECIMAL srem 218 20 PRINTS INPUT "BASE ";B irem 149

30 INPUT"NUMBER";B? srem 161

40 L=LEN{B?):XP=L-lsFORI=lTOL:DM?=MID$(B$

,1,1) :rem 198

50 IFDM$<="9"THEN DM$=STR$ (VAL{MID$ (B?, I,

1))} :rem 233

60 IFDM$=>"A"THEN DM$=STR? CASC( DM? )-55 )

:rem 173 70 D=D+(VAL{DH$) )*BTXP;XP=XP-1 srem 40 80 NEXT: PRINTS PRINT" {3 SPACES} "B?" ="D"DE

CIMAL" : PRINT: RUN srem 205

Binary To Decimal Conversion

10 REM BINARY TO DECIMAL srem 156

20 PRINT" ECLR}" srem 198

30 INPUT"BINARY"?B$ :rem 157

40 L=LEN(B$) sXP=L-lsFORI=lTOLtDM$=MID$(B?

,1,1) :D=D+(VAL(DM5))*2tXP5XP=XP-l

: rem 177 50 NEXT: PRINTS?" ="D; :B$="" :D=0s PRINTsGOT

030 :rem 122 m

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Getting Started With A Disk Drive

Part 4 : Data Files

Charles Brannon, Program Editor

This month, we'll see how to use disk data files and look at some useful techniques when reading and writing to data files.

You save your programs because you know that Random Access Memory (RAM) is transient. Turn your machine off, and it forgets everything you taught it. This is because RAM (specifically, dynamic RAM) is a bunch of little capacitors that need to be constantly recharged (technically, refreshed) in order to hold their ones and zeros.

Incidentally, Read Only Memory (ROM) is made of tiny fuses that have been permanently blown (a rough analogy). Normally, a ROM chip would be full of ones (so electricity can flow), but holes (zeros, areas where current does not flow) are burned into it by selectively blowing the tiny fuses. ROMs are usually created with the fuses "preblown" on the chip. ROMs are used to store information which must not be forgotten, such as the operating system, the BASIC language, and your favorite game cartridge.

By now you understand how to save pro- grams stored in RAM onto disks. But vi'hat about your variables, such as arrays, values, and strings? After someone goes to the trouble to enter his name, social security number, today's date, and a slew of other information, the program does its task, then ends. When you run the program again, the variables are cleared. Even if it didn't clear the variables, you might want to enter new data into

44 COMPUTEI'i GazeHe February 1984

the program. What if you wanted to reference the old data, though?

If the information could be saved like a pro- gram, a whole new world of information-processing opens up. You could search the data for patterns, compute tax, interest, or whatever you dream up. The data could be reused at a later date by another program. If you had some way to preserve your data, you could keep cumulative values such as year-to-date, accrued interest, high scores, etc.

One solution is to enter the information right into the program with DATA statements. It would then be saved with the program. These aren't truly variabk's, though, since your program can only read them, not change them. DATA state- ments can be thought of as read-only variables.

What we need is a way to save variables, as we do programs. Actually, all we really want to do is save the values of the variables. And we don't need to save all the variables, so we'd like to be selective. That way, another program can read the values into variables with different names.

Vw riting data files is fairly easy. You just OPEN a file for write, PRINT all the variables to the file, then CLOSE the file. You use PRINT because it sends out the value of a variable. If A = 5 and X$ = "HELLO", then PRINT A will display 5 and PRINT X$ will display HELLO. That's what you want to do with the file. It should hold a list of all the values you want to save. That way, you can OPEN a file to read, INPUT the values into vari-

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ables, then CLOSE the file.

Data files just substitute the disk for the screen in PRINT, and the disk for the keyboard (you) in INPUT. If you keep this in mind, it will all make more sense.

Let's say you wrote a file out that just con- tained strings:

10 OPEN 1,8,8, "0!DATAFILE,S,W"

20 A$= " HELLO " :B$=" GOODBYE" :C$=" ALOHA"

30 PRINT#1,A$,B$,C$

40 CLOSE 1

The biggest problem

people seem to have with

fiies is not writing them,

but reoding them correctiy.

Don't worry about the details. Just look at line 30. You know what this would do if you PRlNTed to the screen:

HELLO

GOODBYE

ALOHA

That's right, there would be spaces between the items, due to the commas between them. Now let's say you want to read them back in. You might code: INPUT A$,B$,C$. But would this work? If you manually typed in the three items separated by spaces, it would all go into A$, since you know that you have to end each entry with RETURN, or separate it with a comma. So we need to change line 30 to:

30 PRINT#1,A$+", "+B$+", "+C$

This will write the file like so:

HELLO,GOODBYE,ALOHA

just as you would type it in to an INPUT state- ment.

We could also separate it with RETURN by PRINTing the values on a separate line:

30 PRINT#1,A$:PRINT#1,B$:PRINT#1,C$

If PRlNTed to the screen, we would get:

HELLO

GOODBYE

ALOHA

Keeping in mind that CHR$(13) is the same as a RETURN key, we could put it all together like this:

30 PRINT#1,A$+CHR?(13)+B?+CHR$(13)+C$ 16 COMPUTEriGazBftB February 1984

We don't end the last variable with a CHR$(13) because it is at the end of the line. Again, keep in mind how the variables would look on the screen. You have to write the data out so that INPUT can read it in properly.

1 ime for details. You OPEN a file to the disk drive as we did last month, but you give it a filename (like you do with SAVE and LOAD):

10 OPEN 1,8,8, "0:DATAFILE,S,W"

In the above statement, the 1 is just a number we'll use to refer to the file. The second number, 8, refers to the disk drive. It will always be 8 with the disk, unless you have another drive set up as device 9. The third number is also an 8, and this is somewhat arbitrary.

When you write or read data to or from a file, it isn't stored on the disk (during output) or sent to the computer (during input) until 256 characters have filled a disk buffer. The buffer is then sent to the computer, or written to a sector. This is be- cause a disk sector is 256 bytes long, and you have to read or write a whole sector at a time.

There are 13 of these buffers available for your use, numbered 2-14. The number 15 is reserved for the command channel, and buffers 0 and 1 are used by BASIC for SAVE and LOAD. You can use any number for 2-14, but if you have more than one file open at one time, you have to use a dif- ferent buffer number for each one.

Finally, we have the filename. It is a string, so it is enclosed in quotes. You could also do some- thing like:

10 INPUT "FILENAME" ;F$

20 OPEN 1,8,8, "0!"+F$+",S,W"

The "0:" is used for the same reason we used it with SAVE. It's not strictly necessary, but we've observed occasional problems when it is left out. The suffix ",S,W" can be spelled out:

20 OPEN l,8,8,"0i"+F$+",SEQ,WRITE"

SEQ means a sequential file. For our use, SEQ just denotes a data file, as opposed to a PRG (program file). There are a few other file types, REL (relative) and USR, but we won't cover them here. The "W" means write, and is necessary, since the OPEN statement otherwise has no way to tell the disk whether we want to read or write to the file.

If you need to replace an existing file on the disk, you could use "(a'O:" in place of "0:", or open the command channel and send a SCRATCH command to delete the old file before you write the new one.

After we OPEN a file, we just PRINT# (say "PRlNT-file") our values to it, as we discussed above. Here are some examples:

COMPUTE!

Boole

AUTUMN

19 8 3

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•14.95

l5BN0-94Z38e-1 1-6

Machine Lansuage For Beginners. Much com- mercial software is written in machine language be- cause it's faster and more versatile than BASIC. Machine Language For Beginners is a step-by-step introduction to the subtleties of machine code. Includes an assembler, a disassembler, and utilities, to help be- ginners write programs more quickly and easily. Covers many popular home computers.

350 pages, paperback.

Spiral bound for easy access to programs.

I

COMWiasl-i;-- ■ "-COMMOlVJivl:-

64

I

'12.95

ISBN 0-942386-20-5

COMPUTErs First Book Of Commodore 64. An

excellent resource for users of the 64, with something for everyone: BASIC programming techniques, a memory map, a machine language monitor, and information about writing games and using peripherals. Many ready-to-type-in programs and games.

VIC

2

CCfrfl^ltl SocootJ Book ctf VC

'12.95

ISBN 0-942386-16-7

COMPUTEI's Second

Book Of VIC. This is just the book to follow the bestselllng First Booli of VIC: clear explanations of programming techniques, an extensive memory map, a mini-word processor, a system for creating sound effects, a custom character maker, a machine language assembler, and "Snake," an extraordinary all- machine language game.

274 pages, paperback.

Spiral bound for easy access to programs.

264 pages, paperback.

Spiral bound for easy access to programs.

Prosfammer's IteterencB

Guide

to the

TI-9g/4A

•CiciimaH

>4*J E«^ Stv *-! E^] -UF,

312 pages, paperback.

Spiral bound for easy access to programs.

'14.95

ISBN 0-942386- 1 2-4

Programmer's Reference Guide To The TI-99/4A.

Useful for everyone from beginners to experienced programmers. Contains in- structions for program- ming in BASIC, plus more than 40 ready>to-type-ln programs for this popular computer. Explanations and examples of variables, files, arrays, high-resolu- tion graphics, music, speech, editing and debugging, conserving memory, and more.

'12.95

ISBNO-942386-OO-O

COMPUTEI's First Book Of Atari. One of the most popular books for one of the most popular personal computers. Useful articles and programs include: "In- side Atari BASIC," "Adding A Voice Track To Atari Pro- grams," "Designing Your Own Atari Graphics Modes," and more. For be- ginning to advanced Atari owners and users.

(84 pages, paperback.

Spiral bound for easy access to programs.

•12.95

ISBN0-942386-06-X

COMPUTEI's Second Book Of Atari. Previously unpublished articles and programs selected by the editors of COMPUTE! Mag- azine. An excellent resource for Atari users. Contains chapters about utilities, programming techniques, graphics and games, applications, and machine language.

250 pages, paperback.

Spiral bound for easy access to programs.

'12.95

ISBN 0-942386-08-6

COMPUTEI's First Book Of Atari Graphics. Atari programmers interested in graphics and color will find this book indispensable. Includes sections on using Atari graphics, "painting" the screen in 25& colors, mixing graphics modes, making high resolution graphs and charts, redefin- ing character shapes, player/missile graphics, and much more.

'19.95

ISBN 0-942386-02-7

248 pages, paperback.

Spiral bound for easy access to programs.

108 pages, paperback.

Spiral bound for easy access to programs.

Inside Atari DOS. An in- valuable programming tool for intermediate to ad- vanced Atari programmers who own a disk drive. Written by BUI Wilkinson, designer of Atari's Disk Operating System, this book provides a detailed source code listing. A com- prehensive guide to DOS structure.

MAPPING

THE/mmi

^SiL,

'14.95

ISBN 0-942386-09-4

ITte Atari BASIC

SOURCE

: ( • •

' ( ftja¥»»€iu<Mi- ■

Mapping The Atari. A

"treasure map" of ROM and RAM. This book sup- plies a comprehensive list- ing of memory locations and their functions. In ad- dition, many applications are suggested, complete with program listings. For beginning to advanced Atari owners and users.

'12.95

ISBN 0-942386- 1 5-9

The Atari BASIC Sourcebook. From the computer's point of view, each BASICcommand is actually a machine language miniprogram. Authors Bill Wilkinson, Kathleen O'Brien, and Paul Laughton, the people who actually wrote Atari BASIC, have compiled a complete annotated source code listing and a wealth of information on the internal workings of BASIC,

194 pages, paperback.

Spiral bound for easy access to programs.

296 pages, paperback.

Spiral bound for easy reference.

12.95

ISBN 0942386.07-8

COMPUTEl's First Book of VIC. The essential refer- ence guide for owners and users of Commodore VIC- 20, the computer In more homes than any other. First Book of VIC features games, educational pro- grams, programming tech- niques, home applica- tions, machine language, memory maps, and more.

212 pages, paperback.

Spiral bound for easy access to programs.

3.95

90 pages, paperback.

Revised and updated 1983 edition.

ISBN 0-942386- 22-1

The Beginner's Guide To Buying A Tersonal Com- puter. This useful hand- book is designed to teach the novice how to evaluate and select a personal com- puter. Written in plain English for prospective buyers of home, educa- tional, or small business computers. Comes com- plete with personal com- puter specification charts and a buyer's guide to 35 computers.

•n

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h '12.95

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^■^Every Kid's"«i"

First Book of Robots and

0!

COMPUTEt's First Book Of VIC Games. Two

dozen great games for just SI 2.95. Each has been tested and debugged and is ready to type in. Con- tains a variety of action games, mazes, brain testers, dexterity games, and more. Helpful hints and suggestions explain how each game was put together, strategies for winning, and ideas for modifying the games.

201 pages, paperback.

Spiral bound for easy access to programs.

83 pages, paperback.

'4.95

ISBN 0-942386-05- 1

Every Kid's First Book Of Robots And Computers.

This book uses turtle graphics to introduce kids to robots and computers. Includes exercises for com- puter graphics languages such as Atari PILOT. Addi- tional exercises allow readers to experiment with the Milton Bradley ■'Big Trak™." Children who don't have a computer can use the sturdy "Turtle Tiles^'''^" bound into each book.

Big TrAk i-, A rr^dfnijf k of [he MIIEon Br,sdl*y

Company.

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ATARI GAMES

'12.95

ISBN 0-942386-14-0

COMPUTEt's First Book Of Atari Games. Here are fifteen commercial quality game programs, ready to type into an Atari. The book contains fast machine language games that require quick reflexes as well as brain testers that feature strategy and logic. As a bonus, many programming techniques are explained in depth, so Atari owners can adapt them to their own games.

I

Home Energy Applications

On Vour Pcrionjil Computer

'14.95

ISBN0-94Z38S-I0-8

Home Energy Applica- tions On Your Personal Computer, Written for homeowners who want to analyze energy costs. In- cludes many computer programs for adding up the costs and benefits of home improvements — weatherstripping, insula- tion, thermostat timers, air conditioning, storm windows, and so on. Pror grams will run on all popular home computers.

232 pages, paperback.

Spiral bound for easy access to programs.

243 pages, paperback.

Spiral bound for easy access to programs.

New Releases October-December 1983

COMPUTOs First Book Of Tl Games $12.95

ISBN 0-942386-17-5

19 ready-to-type-in games, including mazes, chase games, thinking

games, creative games, and many explanations of how the programs

WOflt.

COMPUTEIs Second Book Of Atrtri Grapfiics M2.9S

ISBN 0-942386-280

Dozens of easy-to-understand explanations of rainbow graphics, animation, player-missile graphics, and more — along with artists utilities and advanced techniques.

CreAting Arcade Games On Ttie VIC S12.95

ISBN 0-942386-25-6

Everything you need to know to write exciting fast-action games In BASIC on the VIC. from game design to techniques of animation, in- cluding complete example games.

VIC Games for Kids $12.95

ISBN 0-942386-35-3

30 games written just for kids (though adults will enjoy them too). Ac- tion games and games to teach math, geography, history — learning has never been more fun.

COMPUTEI's First Book Of 64 Sound & Grapliics $12.95

ISBN 0-942 386-Z 1-3

Clear explanations to help you use all the 64's powerful sound and video features. Plus great programs for music synthesis, high-res art, and sprite and character design.

COMPUTEI's Tliird Book Of Atari $12.95

ISBN 0-942386-18-3

Continues the COMPUTE! tradition of useful and understandable infor- mation, with programs from games to a word processor. Plus utilities and reference tables.

COMPUTEI's First Book Of Commodore 64 Games $12.95

ISaNO-942386-34-5

Packed full of games: Snake Escape. Oil Tycoon. Laser Gunner. Zulder Zee. Arcade-action machine language games for fast hands; strategy games for sharp minds.

COIVlPUTEl's Reference Guide To 64 Graphics $12.95

ISBN 0-942386-29-9

A complete, step-by-step tutorial to programming graphics. You'll like the clear writing, the example programs, and the full-featured sprite, character, and screen editors.

Programmer's Reference Guide To The Color Computer $12.95

lSBNO-942386-19-1

An essential reference. Every command In regular and extended BASIC is fully defined, with ideas and examples for using them. Plus chapters on planning programs.

Creating Arcade Games On Tfie 64 $12.95

ISBN 0-942386-36-1

The principles and techniques of fast-action game design. Including custom characters, movement, animation, joysticks, sprites, and sound- With complete example game programs.

Commodore 64 Games For Kids $12.95

ISBN 0-942 386- 3 7-X

Dozens of games for kids of all ages, making this an instant library of

educational software. Learning, creativity, and excitement .

Things To Do In 4K Or Less $12.95

ISBN0-942386-38-S

Many entertaining and Intriguing programs for small-memory com- puters like the unexpanded VIC, Color Computer, and T1-99/4A, with tips and hints for your own 4K programs,

Creating Arcade Games On The Timex/Sinciair $12.95

ISBN 0-942386-26-4

Features five ready-to-type-in games, along with the principles of game design. Also serves as an excellent Introduction to BASIC pro- gramming on the Timex/Slnclalr.

Coming Soon (Early 1984)

• The VIC Tool Kit: Kernal &. BASIC

• Mapping The VIC

• Mapping The 64

• The 64 Toot Kit: Kernal 8s BASIC

• Creating Arcade Games On The TI-99/4A

• All About The 64: Volume I

• Tl Games For Kids

• The Anything Machine: TI-99/4A

How To Order

All orders must be prepaid, in U.S. funds (check, money order, or credit card). NO residents add 4% sales tax. Please alfow 4-6 weeks for delivery.

Send prepctld orders (including $2 shipping,/ Or call

handling for each book) to: TOLL-FREE

COMPUTEI Books 800-334-0868

P.O. Box 5406 (9 1 0-275-9809 in NC)

Greensboro. NC 27403 between 8:30 AM and 4:30 PM. EST. Monday-frldtiy

CommocofG 64 cnG VIC - 20 u re fraderrrafki of Corf\rnoclofo [iusjnOH Mgct'i-ne^ orid/or Con^rnodore Elec^o^lics. Ltd- AJorj is □ iracemqrk of Atari, Inc. Tl-'?^ is o Todenr^Qrk ot To^as in^trumer^ts.

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Save a numeric array:

20 FOR 1=1 TO 10 30 PRINT#1,A(I) 40 NEXT I

Save a two-dimensional string array:

20 FOR 1=1 TO 3

30 FOR J=l TO 6

40 PRINT#1,A?(I,J)

50 NEXT J, I

Save mixed variables:

20 PRINT# 1 , NAME$ ; " , " ; AGE ; " , " ; DATE?

X^fter you PRINT out all the data you want, you have to CLOSE the file, for three reasons. First, you may want to reuse the file number later in the program, and CLOSE makes it available. Sec- ond, you can have a maximum of only ten files open at once, so you want to free up a file once you're through. Third, you have to do it anyway. Otherwise, the contents of the last buffer may not be written to the disk. Remember that a buffer will not be written until it fills up with 256 charac- ters. When you are finished sending data, the last buffer might not yet be full. CLOSE makes sure the incomplete buffer is written out.

To use CLOSE, just follow it with the file number: CLOSE 1 will do. You can even CLOSE files which have never been OPENed without causing an error, so some people routinely CLOSE a file before they OPEN it to prevent the ?F1LE OPEN ERROR that results when you try to open a file that is already open.

The biggest problem people seem to have with files is not writing them, but reading them correctly. A common mistake is reading the values out of order, or trying to INPUT a string value into a numeric variable. If you remember how the PRINT and INPUT commands work, though, you shouldn't have any problem.

This will open a file named "DATAFILE" which was previously written:

100 OPEN 1,8,8, "DATAFILE, S,R"

Actually, you can shorten it to:

100 OPEN 1,8,8, "DATAFILE"

because the disk drive assumes you want to read the file unless you say otherwise, and it will know the file is SEQuential when it finds it.

You can then use the INPUT# command to read the file in the same way it was written:

110 INPUT#1,A$

Since you are reading values, not variables,

you can use any variable name you like.

Here are some examples of INPUT#, fol- lowing the previous examples. If you parallel your INPUT# to your PRINT#, you can't go wrong:

Read a numeric array: 120 FOR 1=1 TO 10

130 INPUT#1,A{I) 140 NEXT I

Read a two-dimensional string array:

120 FOR 1=1 TO 3

130 FOR J=l TO 6

140 INPUT#1,B$(I, J)

150 NEXT J, I

Read mixed variables:

120 INPUT#1,N$,A,DATE9

As shown, you don't have. to use the same variable names. Just keep the values in the same order.

After you are finished reading the file, CLOSE it to keep things tidy.

Vw e'll now get into some file techniques. Our examples have been pretty simple, always as- suming that the same number of items is always written out. But if you don't know how long the file is, how do you know when to stop reading?

10 INPUT "NUMBER OF NAMES" fN

20 DIM A$(N)

30 FOR 1=1 TO.N

40 PRINT "NAI-IE #",'!;"!";

50 INPUT A$(I)

60 NEXT I

70 OPEN 1,8,8, "0:NRMEFILE,S,W" t

80 FOR 1=1 TO N

90 PRINT#1,A$(I)

100 NEXT I

110 CLOSE 1

This program asks for a list of names, getting the number of names to be entered from the user. It then writes the names to a disk file called "NAMEFILE". Now, if you want to read the names with another program, you don't know how many names were written. The solution: Write N, the number of names, to the file. We can add line 75 to do just that:

75 PRINT#1,N

We can then easily write a program to read the file:

10 OPEN 1,8,8, "NAMEFILE"

20 INPUT#1,N

30 DIM A$(N)

40 FOR 1=1 TO N

50 INPUT#1,A${I)

60 NEXT I

70 CLOSE 1

Another method is to write an end-of-file marker, say an asterisk, at the bottom of the file. Then we can read the file until we reach the as- terisk. There's another way, too. The computer changes the STATUS variable when it detects an error (STATUS normally equals zero). One such error is end-of-file. If line 75 were not added to the program that writes the file of names, we could still read the file like so:

by

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the first truly easy-to-use spreadsheet ^for your 71020" or Commodore 64'

Do you feel lost in o sea of un- ending popefwork? Out. hove you been woiting to purchase o spreadsheet progrom until one wos mode thot Is easy-to-use? Wait no more . . .CSP'Colc was designed for youl CSP'Colc runs on both the Commodore 64"" ond the VIC 20~ with 24K odded. This means you can "step -up" from o VIC-20"' to o Commodore 64'", without needing to purchose a new spreadsheet. Plus, os with our other programs, you even hove the option of printed spreadsheets on your Commodore™ compatible printer, CSP » Cole 'Smoxl mum spreodsheet size is limited only by your computer's memory. This meons that on o VfC-20'", you con get approximotely 1000 cells, ond on a Commodore 64'", opproxlmately 2000 cells. Plus help screens ore available to you os you use the progrom.

The two-color manual comes in a three ring binder with dividers, o quick reference eord, llberol use of exomples and on Index, It's o siep-by-step guide thot will oilow even novice users to operote the spreadsheet program. The screen commonds ore printed in 0 contrasting color to moke it eosler to use. We hove olso Iricluded complete examples of o utility cost spreodsheet, o stock portfolio onolysis and a rental Income onalysfs,

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10 OPEN 1,8,8, "NAMEFILE"

20 DIM A?(50) !N=1

30 INPUT#I,A$(N)

40 IF ST=0 THEN N=N-H:GOTO 30

50 CLOSE 1

By the way, if you want to look at the names as thev come in, you could acid a line that will PRINT AS(N) after the INPUT#.

X ou can also open more than one file at once. This program opens the file we created earlier and writes it to a new file. Along the way, it changes every occurrence of "JOE" to "JACK" (don't ask why):

10 OPEN 1,8,8, "NAMEFILE"

20 OPEN 2,8, 7, "0:NEWFILE,S,W"

30 INPUT#1,A?:S=ST

40 IF A$="J0E" THEN A$="JACK"

50 PR1NT#2,A?

60 IF S=0 THEN 30

70 CLOSE 1

We save the value of ST in the variable S, since the PRINT#2 in line 50 may reset it, and we don't want to lose the end-of-file indication.

You can also use GET# to read from a file. This program dumps any data file to the screen:

10 OPEN 1,8,8, "FILENAME"

20 GET#I,A9:S=ST:PRINT A$; : IFS=0THEN20

30 CLOSEl

Now maybe you want to examine the file as a bunch of ASCII numbers. You might type:

20 GET#l,A$:S=STiA=ASC(A$)

Stop before you go any further! There is a problem here. If the program contains any im- bedded CHRS(0)'s, ASC will cause an 71LLEGAL QUANTITY ERROR, You see, CHR$(0) is read by GET as the null string, and ASC will not work on a null string. CHR$(0) is not the same as the numeral 0, which has an ASCII value of 48. In- stead, use:

GET#1,A$:S=ST:A=ASC(A$H-CHR$(0) )

The ASC function gives you the ASCII value of the first character of the string. Unless A$ is a null string, the appended CHR$(0) won't affect anything. But if A$ is null, then ASC will see the CHR$(0) and return 0, which works fine, A con- fusing situation, to say the least.

Next month, we'll conclude this series with some miscellaneous material, including answers to frequently asked questions about disk drives. I've shown you only a glimpse of the power of data files. Your disk drive expands your com- puter's memory, as well as its processing capabilities. Don't treat your disk drive as a glorified cassette unit. Its speed, random access, and convenience can really open up a whole new world of computing capability, 9

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HOTWARE

A Look At This Month's Best Sellers And The Software Industry

Kathy Yakal, Editorial Assistant

	This		Last	This		Last
	Month	Month	Month	Month
Commodore 64 Entertainment		VIC-20 Entertainment
	1	Jiimpman (Epyx)	2	1	Gridrunner (HesWare)	1
	2	Temple of Apshai {Epyx)	3	2	S/wm us (HesWare)	3
	3	Fwgger (Sierra On-Line)	4	3	Temple ofApshai (Epyx)	4
	4	Fort Apocalypse (Synapse)	1	4	Cboplifter (Creative Software)	3
	5 6	Owplifler (Bvibderbund) Gridrtiimer (HesWare)	6 7	5 6	Crush, Crumble and Chomp (Epyx) Predator {HesWare)	5 7
	7	Neutral Zone (Access)	8	7	Attackof the Mutant Camels
	8	Plaiietfall {Iniocom)	5		(HesWare)	_
	9	Teletigard (Avalon Hill)	-
	10	Wj^ness(Infocom)	—	VIC-20 Home/Business/Utility
		Commodore 64 Home/BusinessAltllity		1 2	Quick Brown Fox (Quick Brown Fox) Turtle Graphics (HesWare)	1 2
	1	WordPro 3 Plus/64 With Spell Right		3	Household Finance
		(Professional)	1		(Crea Ei ve Soft ware)	5
	2	Quick Brown Fox (Quick Brown Fox)	2	4	HESMon (HesWare)	4
	3	HomeAccoutitatitiContinenta])	-	5	TOTL TimeManager {TOIL)	^^
	4	Orflc/e (Batteries Included)	10	6	TOTlText {TOIL)
	5	MF!7e(MSoft)	3
	6 7	Paper Clip (Batteries Included) Money Manager (Timeworks)	9 4		VIC-20 Educational
	8	Mariagement Systems 64 (Entecii)	-	1	Touch Typing Tuior (Taylormade)	1
	9	Data Base 64 (Entech)	-	2	7'i/;)f/l/;«cA:(Sirius)	3
	10	HESMon (HesWare)	-	3	Word Search {TkF)	-
	Commodore 64 Educational	4 5	SkyMath{\JM\) Primary Math Tk for (Comm* Data)	2
	1	uungeons o} the Atgevra Uragorjs (Timeworks)	5
	2	Pacemaker (Spinnaker)	1
	3	Sf»dio64(Enlech)	-
	4	Fraction Fmer (Spinnaker)	2				1
	5	Up For Grabs (Spinnaker)	3
	6	Primary Math Tutor (Comm*Data)	4
	7	Pipes (Creative Software)	-
	8	Touch Typing Tutor (Ta vtormade)	7
		mmmm

54 COMPUTED Gazelle February 1984

Top 40

Comparing The Software And Record Industries

Kathy Yakal, Editorial Assistant

This month's HOTWARE examines some of the similarities and differences between the personal-computer software industry and the record industry.

Personal computers, some say, cannot be fairly compared to any other consumer product that has existed up to now. Computers are unique; no other technology allows so many applications for so little money.

But interesting parallels-can be drawn be- tween the computer and record industries. You could say that an amplifier/receiver is comparable to a computer; a turntable or tape deck is like a disk drive or tape drive; and that records and tapes are "software," like floppy diskettes and program cassettes.

The analogy is not perfect, of course. A stereo system is useless without software in the form of records, tapes, or radio broadcasts, but a computer can be programmed by the user to perform an infinite number of functions. In that sense a com- puter is more like a musical instrument, a creative tool.

True, with a stereo cassette deck, you can record off the radio, or make a copy (in violation of copyright laws) of a friend's cherished Beatles album, just as you can copy a spreadsheet program with a computer. But computers are multifunction machines. Some people argue that for a stereo to be comparable to a computer, it would have to be

easily convertible into a dishwasher or a micro- wave oven or a vacuum cleaner. You can play different kinds of music on a stereo, but it's not exactly the same as running different programs on a computer.

Further, the potential of the two industries is very different. Altliough audio technology is im- proving rapidly (largely because of computer tech- nology, in fact), stereos will always remain, basic- ally, music-playing machines. But we can hardly imagine what computers will be like someday.

A New Kind Of Software

Kapri International, of Sun Valley, California, has been producing and distributing gospel and clas- sical records for the last 20 years. Its employees have seen itTcredible growth and myriad changes in the record industry.

Now, in 1984, it's one of the large.sl dis- tributors of software for Commodore computers in the country, possibly the largest. Kapri carries well over 1000 different titles from about 100 in- dependent St) ft ware publishers and distributes them to a network of more than 1200 dealers.

Kapri still does some business in record al- bums, but its primary product these days is soft- ware. "We started carrying Atari software in 1980, when we saw that software was going to be a big business," says Kapri president Chris Soular. "Record sales were beginning to drop off on a national level at about that Hme anyway, due partly to pirating and high prices."

COMFUTEI's GazeXe Fobruaryl984 55

When Commodore announced its VIC- 20 in 1981, Kapri took noHce. The VIC, at $299, was the cheapest microcomputer available at that time. It was a real computer, not just a game machine. And a number of independent software pub- lishers, responding to the public's quick accept- ance, began producing a Jot of software for it.

"We saw lots of potential in the VlC-20," says Soular. "And when the 64 came out in 1982, we knew that Commodore was going to be a hit." Kapri dropped its Atari line and concentrated on Commodore software. Soular still doesn't regret that decision. "Commodore is like the Michael Jackson of the computer industry' today," he says.

Not So Different

Software publishers view piracy as a growing problem, as do record companies. Most programs have some kind of "copy protection" — a way to keep people from making illegal copies — but clover programmers can often break the protection.

"Pirating is not as big an issue for the software Industry as it is for the music business," says Soular. "It is still a lot easier to tape an album or something off the radio than it is to break into a piece of software. But it does cost the industry a lot of money,"

Another similarity, says Soular, is the need for industry people to identify with their potential customers. "There can't be a generation gap there. Not only must we be able to evaluate a product and tell whether or not it is good. We have to know what age group is going to be interested in it, and whether they will buy it."

Generally, records are recorded and software written to appeal to one particular age group. There are, of course, exceptions.

The target age group, Soular thinks, is similar in both the software and record industries. It's young.

"In both businesses, you must have a young enough mind to pick the hits," he says.

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Even though the product he now delivers to retailers is different, Soular finds ho must promote software in some of the same ways he did records. "We still do mailings and print up and distribute newsletters and brochures," he says. "Only now, instead of calling radio stations and record stores, I'm calling computer stores and trade journals,"

Price And Support

Support for retailers is one area where Soular sees differences between the two industries. The Na- tional Association of Records Merchandisers (NARM) is a kind of support group for people in the industry. Retailers and distributors stay in touch through this national network. They keep each other in touch with what's happening and try to plan for the future.

No such organization exists for Commodore software dealers, says Soular, but he is trying to create one. To be called the Independent Com- modore Software Dealers Association, it will set up a network similar to that of NARM's. It plans to work closely with Commodore itself to provide information and resources for dealers. Advertising co-ops (in which dealers receive subsidies for ads) and bulk ordering are expected to give dealers a financial break in the heated price wars with mass merchandisers and discount houses. Soular ex- pects to have IM dealers involved by Christmas.

But differences between the record and soft- ware industries will call for somewhat different strategies. One of the most obvious differences is pricing. "Records started out very cheap and got more and more expensive," says Soular. "When people started selling software for personal com- puters, there was no industry standard. They could have compared it to software for larger busi- ness machines, hut that would have looked ridicu- lous. People wouldn't pay hundreds of dollars for one piece of software they bought to use with a computer that cost S299, So they brought the price down to what they thought was fair.

"So the big guys were charging a lot of money for their software. Along came these little guys who had fairly good packages for a lot less. The big guys had to lower their prices to. keep selling. Prices are getting a bit more reasonable, and I think they'll probably come down some more and then stabilize."

The relationship between product develop- ment and pricing can also be dissimilar in the two industries, notes Soular. "A band could work on an album for five or six months and spend hun- dreds of dollars making a record. Then it sells for S6.99. On the other hand, you've got software writers who can write a program in a month or two — spare time, even — and sell it for S89.95. It's a very young industry, though. Things wilt change." Q|

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Steve Punter

The Programmer Behind

WordPro

Selby Bateman, Assistant Features Editor

When the conversation among Commodore users turns to word processings the name of Steve Punter is usually not far behind. Creator of the hugely successful WordPto word processing package, Punter is a 25-year-oId Canadian-based programmer who has quickly made a name for himself. Here, he offers his comments on the future of WordPro, his ovm approach to writing programs, and the characteristics that separate the top programmers from the crowd.

Steve Punter, author of WordPro

The data processing teachers who used to shoo young Steve Punter away frcini his Toronto high school's Wang 2200 com- puter would today more likely invite him back as a graduation speaker. In those days, every time a data processing class would arrive to use the Wang, there was Punter h Lid died over the hardware.

"I kept pestering them, so they finally had to stop me from coming into the room," Punter says, laughing. "I was banned from going near it." That initial experience with computing in 1976 only whetted his appetite. Now, as a sea- soned programmer with a proven track record. Punter is exploring the farther reaches of word

58 COMPUTEt'sGozBlte F o b ruof y 1 984

processing, bulletin board software, and a variety of other programming areas.

Y'JordPro 3 Plus/64, which Punter has been developing and refining in various forms since 1978, has become the top seller among the Commodore 64 home, business, and utility software packages. Its range of features and ease of use account for its popularity and reflect Punter's approach to programming. In addition to his successes with WordPro, Punter has written all of the software used by Commo- dore bulletin board systems in the United States. He has been running his own bulletin board since April 1981 . After finishing grade 13 in high school (On- tario is the only Canadian province that still has a grade 13), Punter jumped into programming rather than college. The results have been elec- trifying for him. In addition to his heavy pro- gramming schedule. Punter also teaches a course in BASIC at the York Main Library in Toronto. Yet, he has never taken a single computer course himself.

Punter first began programming on a Texas Instruments programmable calculator. The ex- perience convinced him of his interest and his talent. "I learned all of the ropes of programming on that," he says, "especially how to get big pro- grams to fit in little spaces,"

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WordPro originated from Punter's attempt to write a text-editing program rather than a full- blown word processor. But feedback from com- puter users about their word processing needs started him on the trail of something more. With Stuart Martin, who was among the first to recog- nize WordPro's potential. Punter formed Pro-Micro Software Ltd.

Today, after developing successive forms of the program. Punter is writing WordPro 64. This new program, he says, will encompass all the

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features he believes belong in a word processor. Some examples: truly proportional spacing, with separate printer drivers for printers which need them; double-column printing; and screen for- matting that will not break words at ends of lines {parsing), a real boon in proofreading.

X rom his own experiences and observations of other software writers and programs, Punter has some clear thoughts on what separates first-rate programmers from the also-rans: originality, un- derstanding the users' needs and possible mis- takes, and taking the care to create speedy, easily handled programs.

"The ones who aren't the top programmers are the ones who can't come up with their own ideas. They copy everyone else, and they're not going to gain the recognition," he says. "Another step is that you have to understand what the user is going to encounter. A lot of programmers I've seen don't really take that into account. Sub- sequently, those programs are either easy to crash or easy to mix up. It's very important that the progrnms be bullet-proof — that's a word that's been coined over the years. Besides being bullet- proof, a program must be easy to understand."

Many programmers today favor a nuiltiple- menu approach to software, and Punter agrees that the concept is valid. But he also thinks that quick and logical keystroke commands make pro- grams even easier to use. Although he admits his approach may require extra effort of the user at first to learn the commands. Punter is convinced that the end result is much faster and simpler handling over the long haul. WordPro is based on that principle.

A bachelor who lives in one of North Ameri- ca's most exciting cities. Punter gets away from programming with interests In music and video, science fiction reading and conventions, and oc- casional long drives.

"Sometimes I go through periods when I don't do a thing because I just can't come up with anything new. Then 1 get these times when 1 sit down and program and program. It comes and goes," he says.

"I get people around me who say, 'Oh, you're just being lazy' when I'm not working. And some- times I do feel guilty for spending, say, a week or two without doing a thing. But occasionally that's good for me. Then it clears up all of the dead ends I've run into."

Punter is less than certain that ten years from now he will still be writing programs with the same zeal. But in the immediate future, at least. Commodore users can expect a few more inter- esting software products from the author of Y^ordPro. m

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Haunted Mansio

Calvin Overhulser

"Haunted Mansion" is a joystick-controlled action game with colorful and ioiaginative graphics. Written for the VIC with at least 3K expansion, we've added a version for the 64.

An evil witch has captured some friendly neigh- borhood cats and taken tlicm to her haunted man- sion, where she will later turn them into "witch cats." She is out flying on her broom in search of more — so now is your chance to enter the mansion and rescue the cats. The witch's mansion is a maze of corridors, and she has placed the cats in various locations throughout the maze. Your goal is to rescue the cats while avoiding ghosts, bats, and evil spirits.

^2 COMFUTEt's Gazelle Februoryl984

How To Play

After selecting one of six skill levels, use your joystick to maneuver through the maze to one of the cats. When you've got him, return to the bot- tom row of the maze, the only safe spot for felines in this game. If you run into a ghost or bat on your return, you'll drop the cat and lose points. The frightened cat will then jump to another ran- dom location in the maze. The ghosts and bats aren't deadly. When you run into one, you elimi- nate it, but lose points. At the higher skill levels, you'll have to sacrifice points by deliberately running into the ghosts or bats to clear a path to get to a cat.

Your most dangerous enemies are the moving evil spirits (which look like glowing jack-o-

y?i

^^

Pleases the tough

The world may be short of oil. And short of jobs. But there's no shortage of entertainment. Arcades. Movies. Amusement parks. TV Concerts. Records. You've got your choice. And every day, more of you are choosing Hesware'" computer games.

That's because only the best games earn the HesWare title. Tough, challenging, arcade quality action games like Gridrunner;™ Predator,"' Retro Ball,™ and Robot Panic!''

Mind-bending strategy and role playing adventures like Pharaoh's Curse'" and Oubliette:"

Zany new titles that have to be seen to be believed. Would you believe Attack of the Mutant Camels™??

You don't need an expensive computer to enjoy HesWare action, either. HesWare programs are available on cartridge, diskette or cassette for VIC 20r Commodore 64r Atari* and IBM'"' personal computers.

When you pick up a HesWare game, you know it's ready for the toughest test of all: beating out the tough competition for your attention.

HesWare games. Just one of the ways HesWare is expanding the computer experience. Look for them at your fevorite software retailer,

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on a compass, you can see the joystick values in location 830 as follows:

Menacing demom surround Ihe player (right center} in this VIC game of "Haunted Mansion."

lanterns). If you run into one of them, there's no second chance — the game ends, and your final score, skill level, and round are displayed. You will then be given the option to play another game and choose a skill level. The higher skill levels award more points but are more difficult.

For VIC Users

If you have a VIC, you must use a memory ex- pander. If you use a 3K expander, just type in the game (read Typing Tips at the end of the article) and run. If you use 8K or greater expansion, type in the following line before loading or entering the program:

POKE 642,32:SYS 58232

Be sure to enter this line in immediate mode and press RETURN before loading the program, as it is necessary to move the start of BASIC to the beginning of the first 8K expansion block of memory.

How The VIG Version Works

I have included REMs for the major subroutines to show how the program is logically constructed. The main loop is in lines 210-240. Lines 300-307 are used to update the location of the cat saver {the player) and the selected evil spirit. The ON...GOSUB in line 215 for the cat saver and in line 630 for the selected evil spirit allows the new location for either to be calculated using the same subroutines.

To speed up the joystick response, I used a machine language routine which is READ in line 120andPOKEd into the cassette buffer. The DATA statements are found in lines 9000-9040. The SYS in line 210 calls the routine, which places the value of the joystick reading in location 830 and the fire button reading in location 831.

If you think of the joystick positions as points

64 COMPUTEi's CazaHe February 1 98-t

Joystick	Position	Value in S30
None		0
N		1
NE		2
E		3
SE		4
S		5
SW		6
W		7
NW		8

The fire button values are contained in loca- tion 831 as follows:

Fire Button	Value in S31
ON	16
OFF	0

This routine allows the BASIC program to PEEK{830) or PEEK(H31) as needed, and it reads the joystick twice as fast as an equivalent BASIC routine. In this game, the fire button is not used and only joystick positions N,S,E, and W are needed. The beauty of this routine is that it returns all conditions of the joystick and fire button, but you use only the ones you need.

If you've already looked at the game, you've probably noticed the custom characters. The first 64 normal VIC characters are moved by line 110 into Random Access Memory (RAM). Lines ISO- ISO then READ and POKE the DATA statements {lines 10000-10190) for custom characters into RAM. Line 100 lowers the top of memory (only when running with the 3K expander) to protect the custom character set from being obliterated by BASIC. Incidentally, creating the custom char- acters was not such a chore because I used David Malmberg's "Custom Characters For The VIC" program from COMPUTEI's First Book Of VIC. Table 1 lists the custom characters and their screen codes.

"Haunted Mansion/' 64 version.

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Table 1 :	Custom Characters
SCREEN	ORIGINAL	CUSTOM
CODE	CHARACTER	CHARACTER
27	1		Witch
2S	pound	Witch
29	]		Witch
30	t		Witch
31	4-		Evil spirit
35	#		Solid block
36	$		Moon
37	%		Moon
38	&		Moon
39	1		Moon
40	(		Moon
41	)		Moon
42	»		Moon
43	+		Moon
44	t		Roof
45	—		Roof
58	;		Cat saver
59	r		Ghost
60	<		Cat
61	=		Bat
62	y		Space (outside house)

Note that there is n custom character "space' (screen code 62) in addition to the normal space (screen code 32). This allows the same character

Table 2: Program variable Names

VARIABLE DESCRIPTION

A I

J

N O P

Q

V X

AA A$ BL CC CF CL CM

DF

HL

RN

SC

SR

SH

SL

TL

Variable in READ statements.

Misctllnneoits counters in FOR/NEXT

ioops+ randoninumbers.

Random number.

Counter in FOR/NEXT loops.

Constant = 0.

Constant = 1.

Constant = 22.

Volume (36878).

Counter in FOR/NEXTloops + random

numWrs.

Current location to be updated in

subroutines 300-307.

SkilUevel.

String for GET statements.

Flag to place character.

Cat counter.

Cat flag CF= 4 means carrying cat.

Current location forcat saver.

Difference between color memory and

screen memory.

Dead flag.

Constant =32.

Number of current round .

Screen RAM location.

Current score.

Sound high (36876).

Sound low (36875).

Temporary storage for CL or A(l) during

update.

Constant = 35.

Variables for maze generator.

WL

A(0)-A(3)

A(l) — A(13) Locations of evil spirits

to be displayed on the screen with both codes, but allows the program to tell the difference. The normal space is used inside the mansion, and the custom character space is used outside. This keeps the cats, bats, ghosts, and evil spirits from ap- pearing in the sky since they can be placed only in a location containing a normal space.

The game screen is built in lines 1000-1093, and the maze is generated in lines 1200-1292. Variable names, listed in Table 2, are used more than once where possible to conserve memory.

Typing Tips

This is a long program to type in, so be sure to use the keyword abbreviations found in Appendix D of Personal Computing on the VlC-20, which came with your VIC. Don't add any spacesl At certain points in the program, there are only about 100 bytes free when using the 3K expander. If you'd rather not type in the program (VIC version only), send a self-addressed stamped mailer, a blank tape, and $3 to:

Calvin Overhulser P.O. Box 494 Westfard, MA 01886

See program listings on page 185. V

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66 COMPUTEI's GamllB February 1 934

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^ACCESS

NOTHING BUT THE BEST

GENERAL QUARTERS! BATTLE STATIONS! As chief commander of land and sea forces m the Paciflc, your mission is to obtain a qniclt naval victory, and invade enctn> tcrritorv with land forces. [tEACIi-IIKAI),„is a 100% machine lan^^uage game and offers multi-screen action with hi|[;h resolution, three dimensional graphics. (Suggested retail price...$34.95)

NEUTRAL ZONEn, takes you to the outer edges of the galaxy, to ALPHA IV, a long range early warning station whose mission is to detect alien intruders from other galaxies.

NEUTRAL /ONE.,, is the ultimate in high resolution, fast action, arcade quality games. It is written in 100% machine language and features smooth scrolling of the 360 degree panorama. The realism is unbelievable. (Suggested retail price...$34.95>

MEUTRni ionr

l^ltUEter Conmositr

,.r.i B ! .mm " -jtiM -J j.mm i

lACCESS

MASIER COMPOSER.M is the perfect utility for programming music on the Commodore 64. It is fun, easy to use and very powerful. Master Composer takes full advantage of the sound synthesizer to produce all types of music from simple melodies to intricate compositiims. You can compose your own musical scores, experiment with difl'erent arrangements and instruments, program your own accompanyment, or just type in vour favorite sheet music. (Suggested retail price...S39.95)

SPRITEMASTEfT

SPRI'IEM ASTER, n is not just another sprite editor. It's the finest utility available for multicolor sprite animation and game programming. It will have you making full color animated objects in just minutes. People running.birds flying or tanks rolling are a snap with Spritemaster. It will auloinalically append ytmr sprites to either programs. It's easy to use and understand and comes with a full 21 page instructiitn manual and samples of animated sprites to get your started. (Suggested retail price...$34.95)

AVAILABLE NOW AT YOUR LOCAL COMMODORE DEALER

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Ciimmttdiiri' 64 is a roKisliTi'd trademark iif Cunim(id(iri' tiusint'ss Maelilnes, Int'.

Written entirely in ultra-fast machine lan- guage, "Astro-PANIC!" is an arcade-style space game with multicolored sprites and 15 frantic levels of difficulty. Will you be the first human to make it to level 15?

"Astro-PANIC!" is a fast-paced, high-speed, all- machine-tanguage game. The abject is to defend your cannon, maneuvering it left and right as alien saucers dodge and dive in a relentless attack.

Plug a joystick into control port two to play. After loading from tape or disk (see special in- structions below), enter SYS 49152 to run the pro- gram. The screen clears to black with a gray score window at the bottom. Press the i7 funcHon key to begin.

Swooping Saucers

Instantly, seven alien saucers begin to sweep

68 COMPUrEI's Gazelle February 1984

about the screen. Saucers always keep moving in their current direction until they hit a screen boundary, then they rebound, sometimes chang- ing their speed. Meanwhile, you move your can- non left and right to evade the erratic dives and swoops of the saucers. The slightest contact with an alien saucer spells destruction.

Fortunately, you have your Super Weapon, a laser/heat-ray/particJe-beam/thermonuclear ray gun. Simply press the trigger button on the joy- stick to unleash a bolt of this incredible power. The bolt continues until it hits a saucer, atomizing it, or until it reaches the top of the screen. If you hold down the fire button, the bolt continually repeats.

You can pause the game at any time by press- ing SHIFT, or freeze it by depressing SHIFT LOCK. Simply press SHIFT LOCK a second time to continue the game.

Scoring is determined by how close you are to the saucer when vou hit it. Since the saucers

^^s^^j:^^"^^"'

,t.te. -^^.e^e^

■*i^ .. .

for

vjovi^

rves'"

..<?/i^^-

P-'

o.^

is^n

^'^^*^^A»^ore:00r3'^f'^^

Enemy saucers imuliicolored sprites) houer ami dive upon ihe defemiittg player in f/i/s game of "Aslro-PANIC!"

are more dangerous near the bottom of the screen, you get more points for shooting them there. The score is derived from the saucer's position (31 to 210) divided by 8.

If you destroy al! seven saucers, you advance to a new screen. Each level is faster Uinn the pre- vious one and is indicated in the score window (1-15). Be warned — levels ten and above are manic!

You lose a cannon whenever a saucer collides with you. The game is over after you lose all throe cannons to the marauding saucers. The scoreboard keeps track of the high score during the current session. Press f7 to start another game. Watch the time, though: Some people don't know when to quit!

Playing Tips

Keep moving. It is more important to protect your cannon than to make that tricky shot. Dodge the

> ^^■^.vi ^ V w\ \XXV.

Ati lUtdckiitg saucer is zapped at midscreen in level 7.

70 COMPUTEI'sGaielle February 19B<t

aliens first, shoot later. You won't always want to hold down the fire button to repeat, since some- times a shot will be in the air when you'd rather shoot the alien right above you. Keep an eye on the movement of the saucers, so you can some- times synchronize several wipe-out shots. Watch out for the edges of the screen. Aliens will some- times bounce off an edge right into you.

Typing The Program

To type Astro-PANIC!, use MLX, the Machine Language Editor, which virtually guarantees fool- proof entry of machine language programs. You'll find a complete description elsewhere in this issue. Here is the information you'll need to enter Astro- PANIC! with MLX:

Starting address— 49152 Ending address — 50777

After you are finished typing, MLX will let you save the program to tape or disk. Thereafter, just LOAD "filename", 1,1 for tape or LOAD "filename", 8,1 for disk, then SYS 49152 to begin.

During our testing of Astro-PANIC!, no one ever made it beyond level 12. Level 15 is waiting for the truly wired. Keep a sharp eye for any strange-looking lights in the sky.

See program listiitg on page 174. W

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REACT

Don Whitaker

"React" is a fast-action, strategy game for the imexpanded VIC and Commodore 64. A joy- stick is required.

"React" is a colorful, fnst-action game in which your joystick-controlled character, called a "Maynerd," must clear the screen of all the prizes. What's difficult is avoiding the electric fence, the guards (who look like smiling faces, but they're actually leering at you), and your own trail (a solid colored line you leave behind).

How To Play

You begin the game with five Maynerds. Press the fire button to start, After the screen appears, use your joystick to move your Maynerd to one of the colorful prizes. After a few tries, you'll discover that React is not only an action game, but also a strategy game. If you randomly collect prizes, you might find that you've boxed yourself in and can't get to one of the remaining ones.

If you run into the electric fence, a guard, or your own trail, your Maynerd is eliminated. The screen displays your score, the number of Maynerds remaining, and bonus points. Each round gets harder as you have more fences and guards to avoid.

The only real way to amass points or play competitively is to collect bonus points, which are

72 COMFUm'$Gai<Hle February 1984

awarded when you clear the screen in less than 60 seconds. There is no clock on the screen, but you do hear the timer ticking away. The faster you are, the higher your bonus.

Typing In The VIC Programs

Programs 1 and 2 are for the VIC (no expansion memory required), and Program 3 is for the 64, VIC users should use keyword abbreviations (such as ? for PRINT), For a complete list of these, see Appendix D of Personal Couipiiting an the VIC-20 (the manual which comes with the VIC). Also, don't use unnecessary spaces. React uses virtually all of the VIC's memory.

Type in Program 1 and SAVE it twice (just to be safe). Then enter NEW, type in Program 2, and SAVE it twice. Next, LOAD and RUN Pro- gram 1. The screen will display "DO YOU WANT TO CENTER THE SCREEN? (Y/N)." If your TV is a little out of adjustment, use the cursor controls to adjust the screen up, down, right, or left. Pressing RETURN will automatically load Program 2 and run React,

If you're using disk, press RUN/STOP after Program 1 has RUN, and LOAD Program 2.

How The VIC Version Works

Program 1 creates the custom character set and allows you to center the screen. Program 2 is the main game. Here's a description of both programs;

Program 1.

Lines 10-40

50 70 80

120-166

170

10000-10009 Screerccentt-ring subroutine.

Clear screen, chnngc screen colors, print screen- centering upl ion.

Clear screen, change screen coiur to black. Rcser\'ean.irca of memory' for new character set. Copy characters (uppercase letters and non- graphic symLiols) to memory locations 7168-7679. Redefine new characters. Delete Program i, then load and run Program 2,

Program 2.

Lines

5 10

20-28 30-40 109-130 135-136

160

180

190-210

220-240

249

250

260

270 280 290

390

400-420

440-450

460-550

560-580

600-610

Seta maximum volume for game sound.

Clear screen, set charactercolor to black, and

change screen colors.

Print title.

Add sound effects and color to title.

Define variables.

Cause delay while waiting for fire button to be

pressed.

Change screen color to black and switch to

a I te rna te c ha ra c I e r se t ,

Uranch to screen-drawing subroutine.

Randomly color and locate the guards.

Kandomly color and locate the prizes.

Set reaitime clock toL),

Begin m.iin loop. Place Maynerd in starting

position and read joystick.

Check forcollisitm with fence, guard, or trail. On

collision, branch to "lose Maynerd" subroutine.

Check to see if Maynerd has moved.

Cheek to see if Maynerd has collected a prize.

Cause "rvinning feet" sound, increment score,

update Maynerd's position, and return to line

250.

Check to see if fire button was pressed.

Check joystick position.

Draw basic game screen.

Add more fences to screen.

"Lose a Maynerd" subrouhne. Change screen

border to yellow, sound explosion, and check to

see if any May nerds are left,

"You got all the prizes" subri)utine, Cause

sound and color display, determine bonus, and

add it to score.

This Mayjierd has iilwost completed a successful nut in the 64 ivrsiott.

620-650 Display score, numberof Maynerdsloft, and

hmius from previous screen. 660-670 Wait until fire buttun is pressed.

680-720 "Game over" subroutine. Display high score

and mqst current score. Wait for press of fire

button to start new game.

Program Variables

CO Memory location (35879) for screen and border

colors.

SM Screen codo'i'aluefZS) for a guard.

ML .NJumberof Maynerds left.

C Difference fietween screen memory and screen

color memory (30720).

ER Screen code value (32) fora space.

MA Screencode value (0) for a Maynerd.

TR Screen code value (30) for Maynerd's trail.

WA Screen code value (31 ) for electric fence.

S Memory location for voice two (36875).

V Memory location for volume control (36878).

N E Co n s t a n I f or a d d i n g to score .

SC Current score.

NM Number of guards.

NC Numberof prizes.

CL Current numberof prizes still on screen.

JS(X,X) is an array used to translate the joystick position to numbers that correspond to Maynerd's movement. DD, PA, PB, OP, IT, Nl, N2, N3, and N4 are constants used for reading the joystick.

Mai/ucnl ciniuis prizes ZL'hih' {ivoidiii}^ the smiliiij^ guards and his owu Indl in the VIC version.

7A COMPUWi Gazelle Febtuory 1 984

If you'd rather not type in the programs (VIC version only), send a self-addressed stamped envelope, a blank tape, and $3 to:

Don Whitaker

8200 Peiinsi/lviuiiii Wfii/

Thonitou, CO 80229

See program listings on page 181 . 9

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COMPUTING

The New King Of The Mountai

Fred D'Ignazio, Associate Editor

76 COMPUTERS GazeHe Februory 1984

My daughter, Catie, wns born in December 1975. My son, Eric, came along in April 1979, over three years later. Today Eric is four, and Catie is eight. When 1 look at Catie, she always looks bigger than I remembered. When I look at Eric, he always looks smaller.

Catie amazes me because she is growing up so fast. Eric amazes me because he is staying little so long.

I don't know how many times I have wished that, somehow, Eric would catch up to Catie. It's not that 1 wish Eric would physically grow as big as Catie. It's just that I wish he would be as able as Catie at lots of different things — things like

reading, writing, talking, listening, walking, run- ning, minding his parents, drawing, painting. You name it.

This is a big secret that I'm telling you. I've never even shared it with my wife, Janet.

But I'm not the only one in our family who feels this way. Eric feels this way, too. 1 can tell just by watching him struggling to keep up with his big sister. No matter what Catie does, Eric is there, too, trjing to do it. But he is always a little slower than Catie, a little less able.

That doesn't stop Eric from trying. In fact, 1 think it makes him try even harder. And it has made him pick up the habit of jumping into any situation, no matter how difficult and complex, with the expression; "I know how to do it. Let uic do it."

Unfortunately, in most cases Ericiiocsn't know how. But that doe.sn't stop him from trying.

And it doesn't stop me fnim admiring him,

Eric makes me think of other four-year-olds, especially four-year-olds with older siblings, rhey must be a pretty hardy bunch. They are at the bottom of the family totem pole no matter what is going on. They always come in last. Yet they never stop trying. 1 think that's pretty amazing. I know I couldn't do it. It takes a lot of spunk.

The Great Equalizer

Last week we got a new computer product for our Commodore 64 — the KoalaPad from Koala Technologies. The KoalaPad comes with a black plastic stylus (a pencil without a lead) and a soft- ware package, KiMluPainter from Audio Light, all for .SI 25.

KonlaPnititer is a do-it-yourself, create-your- own pictures kit. It is also the great equalizer that has reversed Eric's ptisition in the family. He used io be the least-accomplished artist in the group (with the possible exception oi our fat black cat, Mowie). But now he is the best artist in the family (the best video artist). He is the king of the moun- tain. And he's loving his new position.

The Acid Test

The acid test for any new computer product is whether it lets people do something on the com- puter that either (1) they could not do without the computer, or (2) they could not do as well without the computer.

The KoalaPad and KoalaPniiitcr have dramati- cally passed this test. Eric can do things now on the computer that he could never duplicate on paper. In fact, Eric can do things on the computer that 1 can't duplicate on paper or the computer. And I'm 34.

For a four-year-old, Eric is a pretty good artist. But, using crayons, magic markers, and paper, he is no match for his big sister or, for that matter,

COMPUTEI'iGozeHe February 1 984 77

Bb<

Janet or me. However, using KoalaPainter Eric is more than our match. Eric is now the reigning video-art champ of our family.

When Eric first boots up the KoalaPainter disk he sees a bunch of "menu" boxes on the display screen. When he presses the point of the plastic styUis aj;ainst the Koala Pad, he sees a cross-hairs drawing cursor on the picture screen. By moving the stylus around on the pad, he moves the cursor on the picture screen from box to box.

The boxes let Eric choose the size of his paintbrush, the color of "paint," and the type of drawing he wants to do. Here are some of the boxes that hold Eric's drawing tools. With these tools Eric can:

*DRAW Drawfrcfhand,

* LINE Create "rubber bnnd" lines that stretch across

the screen.

* LINES Connect rubber bands, end to end.

* OOPS Undo his most recent drawing command,

* FRAME Make rectangular frames.

* BOX Draw a framed filled in with a particular color,

* RAYS Draw lines that radiate from a central point.

* XCOLOR Change one color on the screen to a new color.

* COPY Copy a picture or portion of a picture onto a

new screen location.

* MIRROR Create mirrored images simultaneously on the

picture screen.

* CIRCLE Draw circles.

* DISC Draw circles filled with a particular color.

* FILL Fill in any .shape he creates with any color he

chooses. *ZOOM Magnify a picture for detailed drawing,

erasing, or changing. *SWAP View two pictures at the same time. Using

the COPY command Eric can copy portions

ofone picture onto the other picture.

* STORAGE Store his pictures on disk.

* ERASE Erase theentire drawingarea.

i;^i<isL^vi;h.ssis:

This sounds like an overly powerful array of tools for a four-year-old. Don't believe it. They boggle Janet and me, but they do not boggle Eric. He attacks KoalaPainter the same way he charges down the street on his Big Wheels bike— ZOOM!

Rough Drafts

Once, a couple of years ago, 1 had a conversation with Alan Kay, Atari's chief scientist for research and devekipmenl. Kay is also one of the inventors of Smalltalk.

We were talking about the difference between a novqce doing a task and an expert doing the same task. Kay said the key difference was tha