Light Pens And Graphics Tablets: How To Use Them
COMPUTE!
The Leading Magazine Of Home, Educational, And Recreational Computing
$2.95 May 1984 Issue 48 Vol. 6, No, 5
£2,25 UK S326Canado 02W3 __
ISSN 0194-347X ®
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3-D Surface Plotting, A Valuable Graphics Technique
Picture Perfect, A Friendly, Creative Drawing Program For Youngsters
^ Pentominos, A Fascinating Puzzle-Solving Program For ' Commodore 64, VIC-20, > TI-99/4A, PC And PCjr, Atari, And Apple
Plus Snertle, A Challenging Game For The VIC-20, Atari, Commodore 64, And IBM PC And PCjr
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May 1984 Vol. 6, No. 5
FEATURES
20 34
40 44
The Digital Palette: Fundamentals Of Computer Graphics Selby Boteman
Light Pens And Graphics Toblets:
New Woys To Connmunicate With Your Computer Kathy Yakal
The Inside Story: How Graphics Tablets And Light Pens Work Ottis R. Cowper
Realtime Dreaming With Mike Newman Selby Boteman
EDUCATION AND RECREATION
58 3-D Plotting Tim R. Colvin
74 Picture Perfect ForAtori And Commodore 64 CoyV. Ison
82 64 Hi-Res Graphics Editor Gregg Peele
88 Snertle Soori Sivokumaran
REVIEWS
123 Pitstop ShoyAddoms
124 Panic Button For VIC And TRS-80 Color Computer Michael B. Williams
COLUMNS AND DEPARTMENTS
6 The Editor's Notes Robert Lock
10 Readers' Feedback The Editors and Readers of COMPUTE!
126 Questions Beginners Ask Tom R. Holfhill
128 Computers And Society: Computers In The Workplace David D. Thornburg
132 On The Road With Fred D'Ignazio: The Morning After, Part 1 Fred D'Ignazio
136 Learning With Computers: Reody-To-Run Magozines J.B. Shefton and Glenn M, Kleiman
140 The Beginner's Page: A Random Leap Richard Mansfield
148 INSIGHT: Atari Bill Wilkinson
159 Programming The Tl: File Processing, Port 3 C. Regena
162 Machine Language: A Program Critique, Part 2 Jim Butterfield
168 64 Explorer Larry Isaacs
THE JOURNAL
106 142 147 153 165 171 173
176 178 179 180 181 184 190 192
Pentominos: A Puzzle-Solving Program jim Butterfield
BASIC Style— Program Evolution Jim Butterfield
VIC/64 Me mdata Michael M. Milligan
A BASIC Cross-Reference jim Butterfield
Atari Softkey Thomas A Marshall
Atari Line Check Utility Ed Sisul
Commodore Word Wizard JoeW. Rocke
The Automatic Proofreader For VIC, 64, And Atari
A Beginner's Guide To Typing In Programs
How To Type COMPUTEI's Programs
CAPUTEI Moditications Or Corrections To Previous Articles
MLX Mactiine Language Entry Program For Commodore 64
News & Products
Product Mart
Advertisers Index
NOTE; See page 179 before typing In programs.
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GUIDE TO ARTICLES AND PROGRAMS
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COMPUTE! The Journal for Progressive Compuling (USPS: 537250) is published monthly by COMPUTE! Publications, inc., P.O. Box 5406, Greensboro, NC 27403 USA. Phone; (919) 275-9809. Editurial Offices are located at 324 West Wendover Avenue, Greensboro, NC 27408. Domestic Subscriptions: 12 issues, S24. Send subscription orders or change of address (P.O. form 3579) to COMPUTE! Magazine, P.O. Box 914, Farmingdalc, NY 11737. Second class postage paid at Greensboro, NC 27403 and additional mailing offices. Entire contents copyright & 19S4 bv COMPUTE! Publications. Inc. All riglits reserved, ISSN 0I94-357X.
EDITORS NOTES
This month, Richard Mansfield, senior editor o/COMPUTE!, expresses some concerns in this guest editorial about the way progrannning is taught i)i schools. Robert Lock Editor In Chief
Which computer language is best? Ask that question at a com- puter club and you're sure to start a debate. But computer users rarely have much choice in the matter. If you buy a personal computer, you'll get BASIC. It's usually built into the computer. If you learn programming at school, you'll get Pascal. It's built into the curriculum.
Of course, other languages can be purchased for personal computers and are sometimes taught in schools, but BASIC and Pascal are by far the most common ways that most people are learning to communicate with computers.
Why is it that Pascal isn't built into consumer computers and BASIC is frowned upon by academics? What's the difference between these languages? Is Pascal the easier language to learn? Or is it just the easier lan- guage to teacli .
The goal of a teacher is to pass knowledge, even wisdom sometimes, to the student. Good teaching accomplishes this trans- fer with a minimum of damage to the student's creativity and freedom of thought. But like all human activities, teaching can go awry.
On the first day pf driver education, the teacher told me and the two young women in my group that we couldn't get into the car until we'd promised to follow the Three Rules of Good Driving. Evidently there had
6 COMPUTE! Moy19&l
been some hair-raising moments in the past and these rules were for everyone's safety. 1. Keep your eyes on the road at all times. 2. Keep both hands on the wheel at all times. 3. Always use the turn signal, but also roll down the window and signal with your hand too. This last rule struck us as perhaps excessive. For one thing, we'd never seen anyone driving like that. And doesn't rule 3 violate rule 2?
Never mind, that's the way to drive. As the weeks pro- gressed, other strange rules were added: Don't adjust the mirrors or the seatbelt while in motion, never converse with other pas- sengers, and so on. We followed the rules, but of course dis- covered later that these were not realistic guidelines. Some of what we had been taught were the Rules of Good Driver Educa- tion, as distinct from rules of good driving.
I suggest that Pascal is not easier to learn than BASIC. Nor is Pascal more flexible or faster to program in than BASIC. In fact, Pascal has no significant advantage over BASIC save one — it is easier to grade.
That's because Pascal and languages like it stress structured progranming. Pascal has more rules than BASIC. For example, in BASIC you can create variables anytime vou want to. Just say INCOME = 15000 and that's that. In Pascal, you must define your variables at the start of the pro- gram. You must declare whether they're integer, string, floating point, etc.
Another rule associated with Pascal is program formatting: Loops should be indented, each programming event should be on its own line, and subroutines should be set off by additional
spacmg.
A third rule is possibly the most confining: You are not al- lowed to GOTO. In BASIC, this command allows you to branch to any other instruction in the program. And you can keep on branching at will. Pascal permits branching, but you must always return to the place from which you branched.
Forbidding GOTO branches is the keystone of structured programming, and it has an im- portant effect on the way a stu- dent approaches programming. Before actual programming can begin, the programmer must plan the structure of the pro- gram. This is analogous to the requirement imposed by some English teachers that no one should begin writing an essay until they've first constructed a detailed outline. In Pascal classes, flowcharts abound.
Pascal, of course, is not a terrible way to program com- puters. And BASIC isn't perfect. They differ mainly in the psy- chological effects they have on programmers. But if the primary virtue of Pascal is that it is the easier language to teach, maybe some questions should be raised. The most important question might be — is Pascal the best lan- guage to learn?
What's worrisome about Pascal's emphasis on preplanning and its blizzard of rules is that such academic programming might be the only experience many people will ever have with computer programming. They might assume that all computer languages are restrictive. They might never go on to discover that communicating with com- puters can be an exceptionally rewarding, even entertaining, pastime.
follow our path to the future of home computing.
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Futurehouse products are available tor Commodore 64/Vic 20, Atari, TRS-80 Color, and IBM PC jr. computers. When ordering please specify computer, cassette or disk and memory.
Comcisie Pdrtonai Accognnni Eoumale L.jni Pen Piayj.ouno So!l*3re ana Aipnaosi Ccmsiruclion Set ape tfademaiKs or Fuiurenouse Inc Boi UTO Chapel HiII nc 27514 Com- moatjfc 6JpVic 20 Aiit, THS 80 Color ana IBM PC ir a>e legisleita iraaemariis ol CommMo.e Eledromcj LIO Man. Inc Tan(l» Com ano Iplemalionai Business Macnmos Com 'esBec. lively
; Publisher
fditor In Chief
DifeclorolAdministrotion
Gorv ^ Ingetsoli Robert Clock Alice S Wotfe
Senior Ecfifor
ManogingEdilor
Produciion Direct or
Production Edilor
Editor. COMPUTEi's PC & PCjr
Mogazirw
Editor. COMPUTE'-s GAZETTE
Technical Edifor
Assiatdnl Technical Editors
Program Editor
Assistant Editors
Editorial Assistant Programming Supervisor
RictiQfdMcnsfield Kathieen E. Martlnek lony Roberls GoilWolker
TomRHQiftiiil
Lance EEko
Ottis R Cowper
John Krause, George Wtller
Charles Bronnon
Dan Carmichoei. Robert Sims
Todd HeimorcltSelbv Botemur
KothyVakoi
Patrick Parriis In
Assistant Progromming Supervisor Gregg Peele
Technical Assistant Editorial Progrommers
Programming Assisfants
Copv Editors Proofreaders
AdmlnistrotiveAssistontg
Associate Editors
Contributing Editor
Da e McBone
Jetl Homdoni, Kevin Martin.
Chris Poer
Mcrt< Tutt^e. David Florance,
Kevin Mytfytyn
Juonita Lews. Jocn i^ouJeou
Becky i-iQlL Ether aiver.
Dwight Smith
Vlcki Jennings. LaufQ MocFodden. Julio Fleming Susan Voung Sue Booth
Jim autterfteld. Toronto. Conodd Harvey Hermaa Greensboro. t^C Fred [Jlgnazio, 21V Carter tJood S.W.. Roanoke. VA 24015 Dowd Thornburg . P.O. Box 1317, Los Aftos. CA 9.1022 Bill Wiikinson
COMPUlEl's Book Division Editor
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Step In en levy
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Director. Book Soles Si Motttelfrvg Steve Voyotis Aisislani Carol DidteiSOn
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irmaSwnin Janice Fa rv Oe Potter
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Judy TGylor, Usa Fichor+y, Anita
r?oop. Debi Goforth. Jen no
Nosh, Elizobeth While.Sytiil Agee
Jim Coward. Larry O'Conrrar.
Dei Rees, John 6. McConnelt
Eric StQiey. Som Parker.
Eddie Rice, Dcwid Hensiey John
Archilxild, Mary Spragje (Moil
Room Coordinator]
Oota processing Manager Assistants
Leon Stokes
Joan Connpton. Chris Cain
Vice President, Finance &.
Planning
Director. Finance & Planning
Controller
Ac coun t ing Assista nts
Assistants
Paul J Megiioio
R Steven Vetter
James M Hurst
Linda Miller. Dons Hail
Ji!l Pope, Anno Harr«s. ETiilie
Covil. Anne Ferguson, Pot Fulier.
TroceyHutchins
Robert C. Lock Chief Estecuttve Ofticer
<^rv R. Ingersoll. President
Paul J. Megtiola. Vice President. Finar^ce and Planning
Debi Nosh. Executive Assistant
Ccssandra Robinson, Assistont 5vC^^^
Coming In Future Issues
Choosing The Right Printer
A Survey Of Inexpensive Printers
Three Challenging Games For Several Computers: Pests, Devastator, And Olympiad
Lightning Sort
All About Commodore Cassettes
Atari Mocrodos
And Much More...
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Ilie COfv^FUTI! I subscril^er list is made availoble to corefuliy screened organizations wrtri o product or serv.ce wtiicti may tje ot interest to our readers. Jf you prefer not to receive sucti mailings, pieose send or^ exact copy ot your subscription lot^el to: COMPUTE!. P.O. Box 9^A. Farmingdale, f^iY 11737. Include a note indrcoting your preference to receive only your subscription
.Auttiors of manuscripts vvonont IfX3t ol] mcterials submitted to COMPUTliI are original materials witn full ownerstiip rigtits resident In said outhors. By submitting articles to COMPUTE', authors acknowledge ttxjt such materiols. upon occeptance tor publication, lieoome ttie exclusKre property of COMPUTC! Putilicarions. Inc No pxirtionol this mogoane maybe reproduced in any form without written permission from the putllisher. Enhre contents copyright 1.: 1984, COMPUTEI Pubiicotlons. Inc. flights to programs developed end submitted by authors areeKploined in our oijthor contract. Unsolicited moterials not accepted lor publication in COiVIPUfTE' will be returned if outhar provides o self -addressed, stomped envelOF>e. Programs [on tape or disk] must Qccompony eoch submission. Printed listings ore optional, but helpfut Artides should be furnished as typed copy [upper- and lowercase, pieose) wrth double spacing fach pageol your orticie should t^eor the title of the article, dote and name of the author, COf^^PUrEI ossumes no llcblllty for errors in articles or odverti semen ts. Opinions expressed by authors are not necessarily those ot COIvlPUTEt
PFT. Ci^. viC-20 and Coir-.modOfG 64 cie Ircdemcrks ot
Ccmmodore Business MGcnines, ir.c , ond'of Commcdoie Fiecfoncs i,imitcd
Ar^le IS c rroae!Tncr!( ot Apple Compurei ConiDanv
ATARI b o tiDderrrarl* ot Atoil. Inc
vo^'ifl. !5 a trodemofk erf Teiias Insmjir^rts. Inc
' S'^z S^cli CcJor ComDgler -^ a Iicde-Tirak □! Tcnay. Inc
8 COMPUTE! rv4ay1984
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READERS' FEEDBACK
The Editors ond Reoders of COMPUTEi
Can Disks Be Mailed?
Should disks be mailed, and if so, what is the proper way to mail them?
Brian Mangan
Disks can he mailed, as km^ as they are enclosed in a snugli/ fitting, rigid package. Many office supply stores sell padded jackets (called tnailers) especially made for 5V4-iuch disks. Also, for what it's worth, many users ivrite a message on the outside of the mailer, to warn mail handlers that the package contains a magnetic recording which can be damaged by electromagnetic fields.
Commodore Sequential Append
I recently made a discovery that 1 think will help programmers using Commodore disk drives to create and use sequential files. In addition to writing a sequential file (OPEN 2,8,2, "SEQFILE,S,W") and reading a sequential file (OPEN 2,8,2, "SEQFILE,S,R"), it is possible to append a se- quential file. This is a great help; rather than having to rewrite the entire file when additions are made (OPEN 2,8,2,"f" 0:SEQF1LE,S,W"), all you have to do is use an A in place of the W when you open the sequential file for writing: OPEN 2,8,2, "SEQFILE,S,A". The DOS finds the end of the file and simply adds on the new data. You use the regular PRINT#2 statement to accomplish this.
Steve Gibson
Disabling The Atari Break Key
I want to inform your readers about a technique 1 discovered that disables the Atari's BREAK key, but does not need to be reexecuted after each GRAPHICS command. It is so simple that I wonder why no one has ever mentioned it, or if it conflicts with something that I have not yet found out:
POKE 566,143:POKE 567,231 to disable and
POKE 566,84:POKE 567,231 to enable
The preceding statements change the BREAK key interrupt vector to point to address 59279 ($E73F) which contains a machine code PLA and RTI in- struction used by the OS. This method will work
10 COMPUII! May 1984
only with the OS B ROMs, which contain the in- terrupt vector for the BREAK key.
Neil Weisenfeld
ATI Quit Fix
Have you ever hit FUNCTION -f- instead of SHIFT + while you are typing in a program? It's ex- tremely frustrating to see all your work go down the drain. Here's a way to disable the QUIT key on the TI.
To do this you will need either the Mini Mem- ory or Editor/ Assembler cartridge or Extended BASIC and the 32K Memory Expansion. This is because the console BASIC does not contain the CALL LOAD subprogram (better known as POKE). Whenever you turn your computer on, type the following line in the command mode: CALL LOAD(-31806,16). This will disable the QUIT key. If vou are using Extended BASIC, use CALL INIT::CALL LOAD(-31806,16). If you wish to return to the Master Title Screen, you can still do so by typing BYE.
Credit for this information goes to the docu- mentation that comes with the TI Forth package.
By the way, does anybody know of a compre- hensive memory map for the TI?
Davin A. Trulsen, Jr.
What's An EPROM?
I would like to know what EPROMs are and what they are used for.
Bob Cullen
EPROM stands for Erasable Programmable Read Only Memory. EPROMs are memory chip's which can "re- member" programs even when the cotnputer's power is sioitched off. Important machine language programs like the BASIC language or the computer's operating system are often permanently stored in ROM, but stand- ard ROM can be programmed only once (lohcn the chip is made). EPROMs, on the other hand, can be pro- grammed by any computer user with a relatively simple peripheral device, the EPROM programmer. EPROMs can also be erased by exposhig them to ultraviolet light. You could use an EPROM to store any machine lan- guage program you use frequently — even to make your ozt^n game cartridges.
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That'll fool the "lurkers;' those CB "see it ails" who get their kicks by watching. Or you can always use the private talk mode for guaranteed one-to-one conversation.
The CB Simulator is just one of CompuServe's many electronic communications options that include a National Bulletin Board, Professional Forums and Electronic Mail. Plus, there's a world of on-line information and entertainment all for the price of a local phone call plus connect time.
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64 Sprite Collisions
I have a Commodore 64, and am having trouble with collision detection with sprite graphics. I use the following line to check for collisions:
IF {PEEK(53278)ANDX) = X THEN action
This is easy to convert to machine language. In all of my programs, this statement is unreliable. Sometimes it detects a collision between two sprites when they aren't colliding, other times it doesn't detect a collision when they are touching, and other times it works just fine.
I've read in past articles that this problem may be caused by "sparkle" on the 64, and that the solution to the problem is to relocate screen memory. I tried that, and it didn't help.
I've also found that by putting a PRINT PEEK(53279) in my programs, the collision regis- ters work every time. But I don't know how to PRINT a PEEK in machine language.
Eric Rotenberg
First, sparkle can cause spurious collisions with sprites, but yoii have to relocate the character set, not the screen, to disable the sparkle. Second, be aware of the nature of the collision register. U is set when two sprites collide, and stays set, even after the sprites have moved away from each other.
Also, the register is cleared whoi i/ou try to read it, so you can't keep doing an LDA or a PEEK to check for different collisions. The first PEEK resets the reg- ister. If the sprites are still touclting, they will then set the collision register again. When you are checking for a collision, save the results of the first PEEK for later use.
BASIC B For The Atari 400 And 800?
1. Is Atari going to make a Revision B of BASIC, as found in the new XL series on cartridge or other
form for the 400 and 800 computers?
2. I've been having trouble with my BASIC car- tridge. Pac-Man works just fine, but when I plug in BASIC, either the screen goes blank, or I get two clicks and the screen goes blank, or it goes right into memo pad mode. This happens after I put in any other cartridge. Can anyone help me?
Kevin Bailey
As far as ive know, Atari has no plans for offering an upgraded BASIC.
Even though ROMs are sturdy, solid-state devices, they can be damaged by static electricity or by being dropped. It's a good idea to ground yourself (hy touching something made of metal) before you operate any com- puter equipment. But your BASIC'S not necessarily bad. You may just need to clean the contacts.
Normally, the contacts are not exposed, but you can stick a pencil or paper clip into the slot to lower the
12 COMPUn". May 1984
protective hood. Then, using a swab and rubbing alcohol, thoroughly clean the contacts, then let the cartridge dry. Incidentally, this is also a recommended procedure for your Operating System board and other RAM boards. You may also want to try some TV tuner cleaner in place of the rubbing alcohol.
We don't knoiv of any problems with one cartridge leaving the machi)ie in a state that prevents it from running another cartridge, especially since the power is cut off between cartridge changes. If any other readers are having similar problems, or have a cure, please lorite in.
Slow Tl BASIC
In his review of Robot Runner for the TI-99/4A in COMPUTE!, January 1984, Tony Roberts stated that games written in BASIC on the TI are notoriously slow because the microprocessor can't interpret BASIC fast enough. I want to clear up any impli- cation that the TMS9900 CPU in the 99/4A is at fault.
TI BASIC is indeed slow, due to the unusual architecture of the machine and the design of the BASIC interpreter. First of all, the RAM in which BASIC programs are stored is not CPU RAM. The 16K of RAM in the 99/4A is maintained by the TMS9918A video display processor (VDP). There are only 256 bytes of CPU RAM in the 99/4A console.
Every time the microprocessor accesses or RUNs a BASIC program, it must request the pro- gram from the VDP one byte at a time, one state- ment at a time. This causes a great increase in execution time, because the microprocessor must wait for the VDP. While the TMS9900 micro- processor is a word-oriented (16 bits) chip, the VDP works in bytes.
The second reason why TI BASIC is so slow is that the interpreter itself is not written in machine language. It is written in another high- level language known as Graphics Programming Language, or GPL. The GPL interpreter is also built into the 99/4A console. Thus, whenever a BASIC program is RUN, a double hiterpretation takes place. This is similar to writing a BASIC interpreter in BASIC for an IBM PC. It is really amazing that the TMS9900 can run BASIC as fast as it does, considering.
Chris Clark
Use Of COMPUTE! Programs
Concerning the "Readers' Feedback" of Sep- tember 1983, you stated that the programs in COM- PUTE! are not in the public domain, and that only people who own a specific issue of COMPUTE! can have access to the programs in that issue. My question is, what if a computer club takes out a
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subscription to COMPUTE!? Would that dub be allowed to place those programs in those issues in its library for all members? And what if a school or public library takes out a subscription? Could everyone who is allowed access to the library be allowed access to those programs in those issues?
Gary Lee Crowell
Sony, the answer in each case is no. You can only use the programs in an issue 0/ COMPUTE! if you own a copy of that issue.
ViC Video Typewriter
I have written a short program that transforms your VIC into a typewriter (without any annoving syntax errors). I use it to practice my typing after school. To disable the program, use the fl key.
Vicky Cwiertnie
10 PRINTCHR$(8) :PRINTCHR$(14)
20 POKE36a79, 26:PRINT"fCLR]"
30 PRINT"** VIDEO TYPEWRITER **"
40 GETA$:IFA5=""THEN40
50 IFA5="{F1] "THENEND
60 IFA$=CHR5(13)THENPOKE3687a, 15:POKE3687
6,220: FORX=1TO50 :NEXT: POKE36876 , 0 70 PRINTA?,- :GOTO40
Atari Tape Verify
Here is a one-line program which verifies that an Atari tape file is recorded properly. The utility works whether you CSAVE, LIST, or PRINT (data) to the tape. It performs essentially the same as Michael J. Barkan's "Atari Verify" (COMPUTE!, August 1983), but is much shorter. This utility can be LISTed to tape and ENTERed from tape, but since it is so short, it is easy to enter it from the keyboard in direct mode (without the line number). Just use this line:
0 CLOSE #l:OPEN #1,4,0,"C:":FOR A = 1 TO 400:GET #1,A:NEXT A
After recording a file on tape and while the pro- gram or data is still in memory, enter and run this utility. Rewind the tape to the beginning of the file and push PLAY. The utility will read the entire file, one character at a time, to insure that the file is recorded properly. Operation will end with an error code. If you get this code, the file was read successfully, showing that it is good:
136 END OF FILE
If you get one of the following error codes, save the file again, since it could not be read by the computer:
138 DEVICE TIMEOUT
140 SERIAL BUS ERROR
143 DATA FRAME CHECKSUM ERROR
The same variable is used for loop control and to
M COMPUTE! May 1984
hold each character as it is read from tape. This way, the loop never ends and will check any length of file. This variable can be changed to one of those in your program, if desired, to avoid adding to the Variable Name Table of your program.
Douglas J. Wilder
Tl Randomness Test
Richard Mansfield's article "Zones Of Unpredict- ability, Part 2" ("The Beginner's Page," COMPUTE!, December 1983) included a program called "Ran- domness Test." Since it wouldn't work on my T1-99/4A, I wrote a similar program. It takes several thousand cycles to get close to even distribution for each number, but it's fun to let it run.
Gaston Porterie
100 CALL CLEAR
110 PRINT "TEST OF THE RANDOM R" , "FUNCT I ON ON THE Tl-99'
120 PRINT "PLEASE WAIT..."
130 T=T+1
140 RANDOMIZE
1 50 >; = I NT ( 10*RND 1 + 1 1 60 A ( X) =A < X ) +1
170 FOR 1=1 TO 10
1 30 P ( I 1 = I NT ( A ( I ) / T * 1 0 0 )
190 NEXT I
200 IF T / 1 00': ■> INT \T/ 1 00) THEN
2 10 CALL CLEAR
2 20 PRINT "AFTER":
NDOMI ZATION"
2 30 PRINT
240 PRINT "RANDOM'
CCURRENCE"
250 S=0
260 FOR 1=1 TO 10
270 PR I NT I , P ( I )
280 S=S+P ( I >
290 NEXT I
300 PRINT '■".■' '
310 PRINT "TOTAL".
320 GOTO 1 3 0
NUMBE
1 30
T ; "CYCLES" ; "OF RA
"NUMBERS'
/.
Easy DATA Statements
Here is a one-liner that I have found very useful while programming many statements that are almost identical. Used in the direct mode it can yield a set of DATA statements that fill the screen. The program can just as easily use POKE, or REM statements, or any combination of these.
FOR X = 100 TO 300 STEP 10:PRINT X "DATA"; NEXTX
Chuck Cole
Constant 1541 Errors
Ever since I bought my 1541 disk drive, I have been getting the errors 23 READ ERROR and 27 READ ERROR. This not only happens on my
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Enter Larry Bird and Julius Erving. Bird — the hustler, the strong man, deadly from outside. Erving —The Doctor, maybe the most explosive player in the history of the game.
We talked to them, photographed them in action, studied their moves and their stats and their styles. Then we set out to create on computer disc an event which may never happen in rea life. We put the two of them together on a dream court of light, for an elec- tronic afternoon of one-on-one.
It wasn't easy. When they talked, we listened. When they criticized, we made big changes. When they gave sug- gestions, we took them.
And it shows. This thing is absolutely un- canny. You actually take on all the skills and characteristics of Bird or The Doctor — their own particular moves, shooting abilities, even strength and speed.
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It's called Julius Erving and Larry Bird Go One-on-One.' You Ve Bird. Or you're The Doctor. And that's the last deci- sion you'll have plenty of time to make.
How we got this year's hottest sports game out of two rather inexperienced designers.
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disks, but also on prepackaged disks. I have read what these errors mean in Appendix B of my disk users guide, but these descriptions don't tell me much.
Could you please give me more information on these errors, and tell me what I can do about them?
Jay Elmore
The fact that this occurs both on your oxiui disks and on commercial disk programs strongly indicates a tmrdzvare problem. Ask the dealer front whom you purchased the drive for the address of the nearest service center and have the drive checked out.
Sprite Data Problems
I am a Commodore 64 owner and I have a question about sprites, I understand how to create a sprite and move it around the screen. I also know how to move more than one sprite, if the data for them is the same. My problem occurs when I have more than one set of data. 1 can't seem to get both sprites on the screen at the same time. The Programmer's Reference Guide doesn't have an example with two sets of data. I would appreciate it if you would help me out.
Seth Hausman
Jim Butterficld replies:
1 can think of tivo possible problems with your sprites:
1. You may have forgotten to link each sprite to its drawing in memory. With normal memory mapping, sprite 0 needs to have its draioing number (usually 11, 13, 14, or 15) placed into memory address 2040, sprite
1 into 2041, and so on up to sprite 7 into address 2047. If you use drawing number 11, the drawing of the sprite should be in addresses 704-766 decimal; for number 13, addresses 832-894; for number 14, addresses 896- 958; and for 15, 960-1022.
2. Many sprite register addresses control all eight sprites at the same time. To turn sprite 0 on, you would POKE 53269,1; to turn sprite 1 on, you would POKE 53269,2; to turn them both on, you would add 1 and
2 and POKE 53269,3. The following table shmos the bit values for each sprite:
Sprite 0-1 1-2 2-4 3-8 4-16 5-32 6-64 7-128
Thus, to turn on sprites 0, 2, and 4, we add 1+4 + 16 and POKE 53269,21.
Be sure that you keep the difference between a sprite number and a drazoing number clear in your mind. Several sprites can u5e one drawing (or "definition"); or a single sprite can be switched from one drawing
16 COMPUH! MO¥l964
to another as it moves its arms, legs, tentacles, or
whatever.
Using Atari Cartridge Memory
I have an Atari 800, and am currently writing a text-adventure game using the Assembler Editor cartridge. I hope to run the program without the cartridge when I'm finished. How can I use the 8K block of RAM used by cartridge (not to mention all those zero-page pointers that the cartridge uses)? Does it have to go to waste? I hope not, because I'll need ail the memory I can get for this thing.
John Bushakra
No, the memory need not be wasted, but you cannot test the program with the Assembler Editor. Just define the memory you need, then assemble your program to disk. The object code will not go into memory, but will become an executable object file on the disk. The syntax is:
ASM„#D:filename
You can then take all the cartridges out of your machine, boot DOS, then Load Binary File. If you make these the last two lines of your machine code
* = S2E0 .WOR START
ivhere START is a label for the start address, your pro- gram will run automatically after it is RUN. Othenoise, you'll have to use Run At Address to start your program 'from DOS.
More Solutions For Tl Cortridge Loading Problems
In the January 1984 "Readers' Feedback," I read a question about TI-99/4A cartridge loading prob- lems. The problem was with lockup of the keyboard and broken screen display patterns after insertion of a program cartridge. The remedy given by COMPUTE! was to clean the contact strips of the program cartridge. I've found this to help, yet also discovered that this is not necessarily the complete solution. The cartridge connector exten- sion that protrudes from the main circuit board may also be at fault. To remedy the problem means disassembling the computer, cleaning the contacts on both sides and both ends of the cartridge con- nector extension. This solved all of the problems I had encountered.
Richard Winslow
About four months after buying my TI, 1 had the same problem with loading the cartridges. ! solved the problem by taking apart the computer and straightening the bracket which the cartridge plugs into. (It was bent.) Works perfectly now.
David L. Jones
Dmmff'
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COAAMODORE 64~ DATA FILES, A BASIC TUTORIAL, by David Miller, is a step-by-step tutorial which takes the
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MASTER MEMORY MAP: COMMO- DORE 64", by Paveiko and Kelly, is a clearly written, friendly guide to all the
Commodore 64""s memory locations — places inside the com- puter which act in special ways. You'll learn lots of special uses, including how to make music or create special characters for video gomes.
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I discovered that slightly lifting the back of an in- place cartridge seems to improve contact. So I cemented a small rectangle of soft black plastic about .1 inch thick onto the cartridge insertion area to lift each cartridge a little.
I also use a "Widgit" (Navarone hidustries) that holds three command modules and prevents some wear and tear on contacts.
John K. Newell
VIC Video Revisited
I made some modifications to Jim Butterfield's program in "Visiting The VIC-20 Video, Part 4" (COMPUTE!, August 1983) that I think your readers will be interested in. Although the program is a little slow, the patterns that result are remarkable.
The program is short, but because of the loops, it runs for a while. To get some really inter- esting three-dimensional patterns, try inputs with a value of 1.02, 1.03, 1.04, etc. The input sets a step value for line 600. An input of 2 will give a gray field.
William B. Broome
100 POKE56,22:CLR
105 INPUT" {CLR}PATTERN #";C
110 POKE36869,222
120 P0KE36a66,144
130 POKE36867,32
200 FORJ=6144T08191
210 POKE J, 0: NEXT J
300 FORJ=0TO255
310 POKEJ+5632,J
3 20 NEXTJ
330 F0RJ=37888TO38911
340 POKEJ,0: NEXTJ
600 FORJ=6100TO8800 STEPC
610 X=128
620 FORK=JTOJ+7
630 P0KEK,PEEK(K)0RX
640 X=X/2
650 NEXTK,J
700 GOTO700
Try adding STEP C to line 620 as well, to get another interesting effect.
Another Kerosene Warning
A letter in your January 1984 issue questioned the use of kerosene heaters near a home computer. You compared the emissions of a kerosene heater to those of a gas stove, and suggested the use of an electrostatic air cleaner as a precaution.
The sulfur content of most kerosene fuels is high enough to create sulfur oxide levels that are technically in violation of EPA clean air regula- tions. These sulfur oxides can corrode exposed metals and cause problems with electrical contacts. Besides the corrosion of metals, the sulfur oxides can cause health problems.
Since the combustion products of kerosene
are gases and not particulates, an electrostatic air cleaner will not help clean the air of sulfur oxides. An activated charcoal filter may help, but this is not a common appliance in most homes. Corrosion problems may not occur with other electronic appliances, such as televisions or radios, because the components are soldered or otherwise perma- nently fixed inside the appliance.
Those appliances which use exposed electrical contacts, such as game cartridges and computer keyboards, are most prone to corrosion by sulfur oxides. Readers should avoid the use of kerosene heaters in a home with a computer, electric type- writer, or silver tea set.
W. J. Tolonen
VIC Graphics And Super Expander
I'd like to share something with other readers who have VIC Super Expanders. We find that it interferes with some programs written for the unexpanded VIC, especially ones with custom characters. When I find such a program, or am told to "remove all expansion devices" for a certain program, 1 add the following as the first line in the program (or enter it in the direct mode before RUNning the program), and the program runs fine with the Super Expander left in. (In the case of two-part programs, insert the lino in the second part.)
POKE51,30: POKE55,0: POKE52,30: POKE56,30: POKE646,6
This has worked on every program I've encoun- tered so far, and what's nice about it is that you are left with the additional memory as well.
Robert M. Bleich
The Whiz KidsV^ere Right
I would like to point out an error in your response to David Smith's question about Whiz Kids (COM- PUTE!, February 1984). You mention that the sprinkler system that they turned on should have shorted out the terminal they were using. You may have missed this, but it did short out. For a while they were successful in keeping the terminal dry by standing over it, using their jackets as um- brellas. But when the water did get to the terminal, it shorted out.
Karen Wilson
COMPUTE! welcomes questions, comments, or solutions to issues raised in this column. Write to: Readers' Feedback, COMPUTE! Magazine, P.O. Box 5406, Greensboro, NC 27403. COMPUTE! reserves the right to edit or abridge published letters. ©
18 COMPUTE! Moy1984
*•#«
*»•••
»sk:
(JP
.•*-.'. ----J. *-
'^■^
pou bypass the bumps, detours
h
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The Digital Palette:
Fundamentals Of Computer Graphics
Selby Bateman, Assistant Editor, Features
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Your computer screen is a colorful gateway to the world of digitized graphics. But to appreciate all the video magic that's available, you first have to understand the basics. Here's a look at the pixel pozver be- hind your computer's video display.
"I remember standing back with everyone else, saying 'There's no way; I'm never going to touch this thing. It's not creative enough,' " says Kari Beims with a laugh. "I took a computer graphics class; it was full of people like me who are in the graphic arts field. And they were petrified."
The "thing" that petrified Beims and her classmates was, of course, a computer; a machine which, when used as a graphics tool, can appear so novel, so daunting, and ultimately so seductive that artists at first ex- posure may be simultaneously attracted and repelled.
Beims and many others have changed their views about the computer as a graphics machine. An artist at Maximus, Inc., of McLean, Virginia, Beims now uses and helps promote her com- pany's new Visualizer, one of a new breed of graphics software
20 COMPUni May 1984
packages for home computers that is as easy to use as it is useful.
"It's a lot of fun," Beims says. "/ can do it, and I have no programming experience. I mean, I walked into here know- ing nothing about computers."
An Undeniable Attraction
Graphic artists like Beims may be among the most perceptive analysts of how well a computer functions as a graphics tool. And although the polls haven't yet closed, Beims and a growing number of other artists are pre- dicting a landslide in favor of the computer.
"It's getting — I hate to use this term because everybody says it — but it's getting user friendly; it truly is," Beims says. "People are starting to ask graphic artists what they need, and the results are beginning to show up in the computer soft- ware and the peripherals. And we need that."
The glow of a computer screen is the first thing that attracts many people to com- puting. You don't have to know anything about pixels, raster scans, character sets, and RGB monitors to appreciate that
something special, something new and powerful is possible when you can decide what ap- pears on a TV screen.
If you want to create color- ful, high-resolution graphics for games, business, or art, today's microcomputers have the capabilities to produce almost any image you wish. Peripherals such as light pens, graphics tab- lets, and touch screens will free you from the restrictions of the keyboard. And graphics soft- ware packages are becoming surprisingly easy and powerful tools for designing anything from pie charts to paintings.
You Don't Have To Be A Genius
A 20-year fascination with com- puter graphics led Joseph Deken to write the text last year for Com- puter Images: State of the Art, a full-color collection of computer artworks. Deken, an assistant professor of computer sciences and general business at the Uni- versity of Texas at Austin, uses an Atari 800 and one of the IBM- compatibles at home. He believes you don't have to be a genius to understand and appreciate com- puter graphics.
"1 use graphics to teach
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Reston has the books which make learning to program Atari"'* computers fun.
HELLO, COMPUTER: AN INTRODUCTION TO BASIC, by Lawrence P. Huelsmon, can help both teen and adult beginners learn BASIC on many computers, including Atari™, using drills, programming problems, games, cartoons and an easy conversational style.
SURVIVAL ON PLANET X WITH THE ATARI- HOME COMPUTER, by Orkin and Bogas, uses the exciting adventures of Vivian on Planet X to teoch kids basic programming concepts and techniques. The fun is Interspersed with short programs.
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illustrated by noted onimotor Bud Lucky. ATARI'" LOGO ACTIVITIES, by Steve DeWitt, provides over 150 activities which encourage young and old alike to be inventive and creative when using Atari Logo" educational language. The book includes five big projects ond on in-depth discussion of Logo."
ADVENTURES WITH THE ATARI", by Jack
Hardy, teaches you how to write adventure games in Atari PILOr', Microsoft BASIC, and BASIC. It includes six actual adventure games to study, type in, and ploy, plus tips and techniques to help you create your own.
A+ PROGRAMMING IN ATARI- BASIC, by
John Reisinger, is a self- study workbook which gives you step-by-step instructions for BASIC programming on the Atari 400, 800, 600XL and 800XL'" computers. Stressing top-down programming in a fun and friendly manner, this book is perfect for school, workshop
and computer camp. If you want to make learning about Atari" computers fun, then make Reston the teacher.
PCjr, the neivfamUy and personal computer from IBM® comes with a bt of bright ideas to help make computing easy.
Tlje keys, for example, are color-coded to help you hit the right ones.
Some software programs come with keyboard overlays to make working with ■ them more convenient
Then there's the keyboard itself
We call it the IBM "Freeboard" became it's free of a...
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conmcting cord.
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about computers in introductory courses at the universit}'," he says. "I'm always concerned with the stereotype that com- puters just have to do with mathematics. And I'm concerned with how to get students who aren't mathematically inclined interested in computers. Graphics winds up being a good vehicle for that."
An important first step in anyone's computer graphics education is the knowledge that capabilities costing thousands of dollars on mainframes just a few years ago are now available on inexpensive microcomputers. Learning the basics of computer graphics can now be inexpen- sive, simple, and often fasci- nating. Once you've picked up a few of the fundamentals, you'll probably appreciate your com- puter's graphics abilities even more.
Have Gun, Will Travel
Faster than the eye can follow — anywhere from 25 to 60 times a second — an electronic "gun" in your television or video monitor discharges a beam of electrons toward the screen. As the elec- trons hit a phosphor coating on the inside of the video display, the individual picture elements which make up your screen — called pixels — arc lighted. This is a cathode-ray tube, the most common television and micro- computer screen display system.
Rapid-fire painting and re- painting of the image on the TV screen is accomplished by the electron gun's repeated drawing of a set number of parallel lines (usually 525) from left to right and from top to bottom. This technique, known as a raster scan, occurs continuously and so rapidly that images appear to move smoothly across the screen.
The creation of characters and shapes on your computer screen is similar to the effects produced when thousands of college football fans use flip cards
24 COMPUTE! Mov1984
tion screen from Penguin Software's The Complete Graphics System.
to spell messages of team sup- port from the stands. The densely packed pixels flip either on or off, and from color to color, in response to directions from the computer. The more pixels, the higher the quaHty, or resolu- tion, of the screen in^age.
A monochrome, or single- color, video display uses one electron gun. Red-green-blue (RGB) monitors use three elec- tron guns, resulting in a higher resolution than the composite video you're used to seeing on a color television set.
Characters, Grids, And Turtles
There are several ways to create graphic images on a computer screen. First, you can make use of the alphanumeric characters — letters and numbers — built into the ROM (Read Only Memory) of your system. Many micro- computers, such as the Commo- dore 64 and VIC-20, have a paral- lel set of graphics characters — various lines, curves, and boxes — built into permanent memory. Using them as building blocks, you can combine charac- ters into a variety of figures. A more time-consuming.
but flexible method for creating graphics is to manipulate the individual pixels. You tell the computer which pixels you want lighted and in what colors by communicating with it in a lan- guage, such as BASIC. In a per- sonal computer which has a high resolution of, say, 320 x 200 pixels, there are 64,000 graphic points which you can potentially control. Locations in your com- puter's memory literally form a video map of what you can ad- dress on the screen.
(For more information on actually creating color graphics on your computer, see COM- PUTEl's First Book of Atari Crnphics, COMPUTEI's First Book ofConuiiodorc 64 Sound and Graphics, and other COMPUTE! books.)
Turtle graphics is a third way of producing images on your screen. Based on the Logo pro- gramming language, turtle graphics helps to teach program- ming and geometric principles. A small triangle on the screen — the imaginary turtle — can be directed to move about the screen, leaving an image in its wake. Intricate patterns can be achieved through this simple.
YOU'VE GOT TO DIG DEEP TO FIND
A MORE EXCITING GAME
THAN MINER 2049ER:
Now, Reston brings Commodore VIC-20" and Commodore 64" owners one of the hottest home computer games ever created— Miner 2049er;" Help the legendary Mountie, Bounty Bob'" chase the dastardly Yukon Yohan through an abandoned uranium mine — all ten levels of it. But you've got 1o avoid the deodly radioac- tive mutants. And watch out for pulverizers, explosives, slides and foils. And grob all the treasure you can along the way. And beat the clock. Any computer game you've played up to nov/ has just been practice for Miner 2049er.'" It's fast and furious, a gold mine of action for the serious computer gamer. And Commodore VIC-20"' and Commodore 64" owners can get it only from Reston, A Creative Pastime" from
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Available ot your local computer retailer or call us at
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Commodore VIC-20 and Commodore 64 are regrstered trademarks of Commodore Computer, Inc.
Ml 204'.->;f and Bounty Bob ore registered Irodemorks of Big five Sofhvore.
ENTER: THE BRADYADVENTURE
If you're bored with the ordinaiy, dreary functions you've been perfonn- ing day -by-day and even games have lost their luster, Brady brings back the adventure! You and your Commodore 64 can enter a whole new colorful worid of excitement - if you're in command.
Brady Communications, Inc., puts you in control of the fun with a complete line of amazingly easy-to- read books, published especially for
you and your Commodore 64. Whether you're a beginner, an advanced user, a whiz kid, a parent, a teacher or a hacker, Brady publishes the books to teach you how to make the most of your computer From BASIC to games, from graphics to sound, from software to debugging, these books vAW let you key into your imagination in micro- time and bring it up on SCTeen. Enter The Brady Adventure— the excite- ment is all yours.
BLAST OFF WITH BASIC
GAMES FOR YOUR
COMMODORE 64
David Busch
This is the first realiy fun approach to BASIC ever devised. The book containing time-tested, highly visual games maizes it easy to learn BASIC progranmiing on the Com- modore 64 computer. It includes 25 games that take advantage of the Commodore's special features including graphics, sound and joy- sticks. The progi'ams are even suitable for customizing for further fun.
1984/128pp/papei/lSBN 0-89303-333 ■2/S12.95
BLAST OFF WITH BASIC GAMES FOR YOUR VIC 20
David Busch
Twenty -five games make it simple to learn BASIC for your Vic 20. With twenty-five, time-tested, highly visual games, this book lets you take full advantage of the fun available on your Vic 20.
1984/128/paper 0-89303-334-0/$12.95
COMMODORE 64:
AN I>JTRODUCTION TO BASIC
PROGRAMMING AND
APPLICATIONS
Larry Joel Goldstein & Fred Mosher
In this volume the master teacher has taken a hands-on approach to BASIC language and practical real- life applications. The book gives a complete and up-to-date account of what the Commodore 64 is and how it works. Page by page, the reader is introduced to DOS and BASIC. It shows how to program for personal and professional needs and includes pro-ams for mailing lists, word pro- cessing, telephone lists, graphics, sound, and file handling— plus exten- sive coverage on structuring, planning, and debugging programs.
1984/288pp/paper/ISBN0-89303-381-2/$14.95
ADVANCED BASIC
PROGl^MVUNC; FOR THE
COMMODORE 64 AND OTHER
COMMODORE COMPUTERS
Michael Richter
This is the next step for the Commodore user who has mastered the basics and wants to move on to more advanced software. In this book, the reader will learn how good programs are written, how to read and use them, how to know a good one when they see it, and how to gain knowledge through the experience of writing advanced software.
1984/204pp/paper/ISBN0-89303-302-2/S14.95
COMMODORE 64: GETTING THE MOST FROM IT
Tim Onosko
Written for users with little or no previous programming experience, this handy guide is the only source with information on all three versions of the Commodore 64. It includes material on both the classroom model and the portable version. It offers a thorough and understandable intro- duction to the cornputer— including a solid approach to BASIC program- ming. It covers word processing, color graphics, and sound.
1983/320pp/paper/ISBNO-89303-380-4/$14.95
BRAIN GAMES FOR KIDS AND
ADULTS USING THE
COMMODORE 64
John Stephenson
Between the front and back covers, this volume contains more than 40 exciting and challenging games. Designed to entertain and educate the reader, it teaches pro- gramming and the application of some very important mathematical concepts, without the pain. The games are short and precise and are targeted toward whose who learn best by doing. They can be played and enjoyed without an understanding of the mathematics involved. This is one volume you'll want to have for fun —for kids of all ages!
1984/160pp/paper/ISBN0-89303-349-9/$12.95
BRAIN GAMES FOR KIDS AND ADULTS USING THE VIC 20
John Stephenson
This is the volume especially for your Vic 20. Containing more than 40 challenging games, the book teaches programming and some basic math- ematical concepts simply in the doing. Be sure and have this book to make your Vic 20 more fun.
1984/16Opp/paper/ISBN0-89303-347-2/$12.95
HANDBOOK OF BASIC FOR THE COMMODORE 64
Fred Mosher & David Schneider
For the beginner, here is the book to buy wth your Commodore 64. It is simply organized by BASIC programming statements so while programming, the user can go directly to the information he needs without confusion or delay. This one-of-a-kind guide contains the same information as the BASIC reference manual supplied with your Commodore, re- written especially for the new user. It presumes no knowledge of BASIC and explains the materials supplied in the manual.
1984/256pp/paper/lSBN0-89303-505.X/S14.95
These and other Brady Books \vritten specifically for your Com- modore 64 and Vic 20 are available at B. Dalton Booksellers, Walden Books, and other fine bookstores and com- puter dealers nationwide. Or, oil 800-638-0220 for information. Brady Communications, Inc. is a Prentice- Hall Company, located in Bowie, Maryland 20715.
but subtly powerful graphics language system.
To Mimic More Closely
As microcomputers become more sophisticated graphics machines, a similar process is occurring with the devices used to draw and paint images on the computer screen. The graphics software now available relies more and more on such periph- eral devices as joysticks, light pens, graphics tablets, touch screens, and mice (defined below).
These peripherals fall into three basic price ranges, accord- ing to research conducted by Koala Technologies, producer of the KoalaPad Touch Tablet and the Gibson Light Pen. You can find game paddles and most joysticks from $15 to $30; trackballs, mice, graphics tablets, and better light pens from $30 to $400; and precision tablets, called digitizers, from S400 on up. (See "Light Pens And Graphics Tab- lets" and "A Graphics Glossary," both in this issue.)
All of these devices attempt to mimic more closely the actual procedure of drawing or painting on a fiat surface, as opposed to the more indirect, less satisfac- tory process of typing in graphics commands on a keyboard. Often, a joystick, light pen, or graphics tablet may be used in conjunction with keyboard com- mands to produce lines, boxes, circles, rays, points, and various fill patterns.
Other commands allow you to transpose and merge images, lock onto and move parts of a picture, magnify sections of an image for more detailed work, save pictures for later use, and select or change colors.
For Atari And Commodore
Kari Beims says that a mouse — a hand-controlled device which rolls on a flat surface to move the screen cursor — is the most successful device for creating
28 COMPUTE! Moy1981
A Graphics Glossary
ASCII: (Pronounced askey) American Standard Code for Information Interchange. A standard code used in microcomputers to represent alphanumeric information (letters, numbers, and symbols). The capita! letter A, for example, is represented in ASCII code by the number 65.
bitmap graphics: A high-resolution graphics plotting technique by which pixels (picture elements) on a computer screen are turned on and off.
CAD: Computer-aided design. The use of computer graphics to help in design development and modification, often eliminating the need to create costly or dangerous prototypes. CAD is usually as- sociated with CAM, or computer-aided manufacturing, character graphics: The text characters that appear on your computer screen when it is turned on, including letters, numbers, symbols, and punctuation marks.
CRT: Cathode-ray tube. A video display terminal, such as a television or video monitor, which uses a beam of electron particles to draw images on a screen's phosphor coating. The electron beam can write on the screen with a single beam or, more commonly, in a series of parallel lines to form an image. (See raster scan and vector scan.)
electron gun: The mechanism within a CRT which shoots a narrow beam of electrons at the screen, creating images. The beam is con- stantly redrawing the screen at speeds usually ranging from 25 to 60 times a second. Monochrome (single-color) displays use one electron gun. Red-green -blue (RGB) displays use three separate guns (one for each color), and have a higher resolution than the composite color displays found on television sets.
fractals: Geometric patterns which, when repeated, can create new
patterns seemingly unrelated to the original forms. Especially useful
in computer generation of detailed maps and duplication oi the
intricacies of many natural objects.
graphics set: The complete set of graphics characters that a computer
can display.
graphics tablet: A pad, usually square or rectangular, on which the
X and Y coordinates of the computer screen can be plotted by the
use of a stylus, or, on some models, your finger, allowing you to
create graphic images.
icons: Graphic symbols, most often used as visual representations of computer software options and procedures. For example, a paintbrush icon would represent the painting option in a graphics software package. Similarly, a trash can icon might indicate a delete option.
image processing: Computer enhancement and alteration of photo- graphs and other graphic images by digitizing a picture into pixels, each of which is then measured for light and color intensity. The pixels can subsequently be manipulated to change the image.
light pen: A stylus which emits low-level electrical pulses and, when pulled across a computer screen, creates an image. Most often used in creating graphics and in interacting with software menu opHons.
graphics. "It's closer to the kind of tools you're used to working with. With a joystick or a light pen, it's a little different. The mouse lets you work flat-on;
you've got more control. And it's closer to the actual produc- tion work you've done before," she says.
Software companies are
Logo: An easy-to-use, graphics-oriented programming language originally developed to help children learn programming and the concepts of geometry.
mouse: A small hand-controlled device which rolls on a flat surface, allowing you to control the screen cursor, draw graphic images, and select from menu options.
phosphor coating: The coating inside a CRT that glows when struck by a beam of electrons. A computer activates an electron gun to draw and redraw graphic images at high speed on the coating, thus producing graphics that appear to move smoothly across the screen.
pixel: Picture element. The smallest graphic point addressable by a computer. Pixels are turned on or off to form the characters and graphic images on a computer screen.
raster scan: A video picture drawn by an electron gun which sweeps horizontally across the screen in a series of parallel lines at a high rate of speed. The most common method by which a microcomputer system displays a screen image.
resolution: The clarity of a video image based on the number of pixels available on the display screen. The more pixels there are, the higher the resolution and the more detailed the screen image.
RGB monitor: Red-green-blue monitor. A high-resolution color monitor which uses three electron guns to produce very clear and crisp images. By comparison, a color television would normally have a composite color video system in which the three primary colors would be blended, producing a lower quality video display.
simulation: Computer graphics created to model reality in appear- ance and usually in performance. Numerous airline companies, for example, use computer-generated flight simulations to help train their personnel.
sprite graphics: Sometimes called movable object blocks (MOBs), sprites are programmable graphics characters that can move around the screen independent of the primary screen image, the background. touch screen: A video screen or plastic screen overlay which allows you to draw, write, and make menu selections from the screen at the touch of a finger or stylus.
turtle graphics: Closely associated with the Logo programming language, the turtle graphics system is most often used in an educa- tional context, especially in teaching children about computer pro- gramming and geometric shapes. A triangular screen cursor (the turtle) moves across the face of a display monitor in response to directions entered into a computer, allowing the user to program a wide variety of geometric graphic images.
vector scan: A video picture drawn by the focused beam of an electron gun, much like a pencil's movement across a piece of paper. This produces a slower, but higher quality, video image than the parallel- line technique of a raster scan.
video chip: A tiny microprocessor on a silicon chip which handles the video data within a computer, assisting the central processing unit (CPU) by managing the screen image.
exploring all types of input de- vices in order to give users the right mix of creative flexibility and control. The newer packages
number of practical applications as well.
One such product is the Visualizer graphics animation
offer more options, and a greater package introduced by Maximus,
Inc., atSoftcon, the international conference and trade fair of the software industry, held recently in New Orleans. Available now for the Atari computer with at least 48K and disk drive, the S49.95 package should be ready for the Commodore 64 in May.
"The goal with Visualizer was to create a graphics program completely for the nonprogram- mer, which would be useful besides just being a creative out- let," says Beims. "The Visualizer gives you the option, in addition to creating slides, of adding ani- mation effects and putting to- gether a slide show using up to 26 screens.
Synchronizing Slides And Sound
"You can synchronize them with an audio track so that you've got a customized audiovisual pre- sentation. You can move the slides ahead manually, or use a timer through the computer," she says. "In addition to being a graphics program, it's useful. You can use it for teaching, train- ing, business and sales presenta- tions, retail advertising, and instructional lessons for the kids at home."
The package uses automatic drawing functions for circles, ovals, boxes, borders, and diagonals, and has 18 different text style options that can be used with graphics. The slides you create can be printed in black and white with an Epson MX (with Graftrax), FX, or RX series printer, or with a C. Itoh (NEC, Prowriter, or other) printer. A joystick is used for drawing, with a variety of colors and brush sizes available.
Two more recent graphics software products which com- bine usefulness with ease of use are The Graphics Magician (on disk for Apple, Atari, and Com- modore at $59.95 and for IBM by the end of 1984) and The Complete Graphics Si/stein (on disk for Apple at S79.95), both from Pen- guin Software.
May 1984 COMPUTC! 29
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r/ie Visualizer by Maximus, Inc., allows a variety of text faces to appear on the same screen with animation graphics.
"With The Complete Graphics System, I basically wanted to set up an all-in-one tool for people to use to create computer graphics," says Mark Pelczarski, founder and president of Pen- guin Software.
Hundreds Of Colors And 3-D Too
The package is compatible with most input devices, and allows three-dimensional line drawings to be reproduced on a variety of plotters. There are over 100 avail- able colors and 96 brushes. Por- tions of any individual screen may be magnified from two to eight times for easier manipula- tion of pixels. And text may be added with graphics in a variety of ways.
Penguin also sells several programs which can be used in conjunction with The Complete Graphics System. Additional Type Sets ($19.95) provides 50 extra typefaces and character sets. Map Pack ($19.95) includes out- line maps of all 50 states, the continents, the U.S., and Cana- dian provinces. Transitions ($49.95) is a presentation system
30 COMPUTi! May 1984
which will let you organize pic- ture disks and turn them into slide shows. More than 35 dif- ferent screen wipes are available. That is, you may clear the screen from top, bottom, left, or right sides; use geometric-pattern clearing techniques and wind- shield wiper effects, among others. Finally, Paper Graphics ($49,95) is a utility that will let you print any high-resolution graphics screen to your printer.
"The Graphics Magician soft- ware is actually two different sets of programs. One is a draw- ing program geared toward people who are going to use it in [creating] other software — like educational software," says Pelczarski. "There's a huge amount of educational software out there that's been done using The Graphics Ma<^iciau."
The Graphics Magician uses machine language animation routines with the same tech- niques that are used on arcade games. Up to 32 independent objects can be assembled in the animating process. The package also includes a high-resolution picture/object builder, which lets
you store hundreds of color pic- tures on a single disk. More than 100 colors are available for use as well.
Screens A La Mode
Almost all of the top-selling microcomputers have extensive graphics capabilities, but you'll want to spend some time learning your own machine's features.
The Apple He, for example, has a high-resolution mode with six colors and 280 pixels hori- zontally by 192 pixels vertically. There is also a 40 x 48-pixel low- resolution mode with 16 colors. Apple's new Macintosh, which uses a monochrome display, has a whopping 512 x 342-pixel re- solution. Obviously, very fine graphic detail is possible with this many pixels.
The Commodore 64 has 16 colors, several modes — includ- ing a 320 x 200 graphics mode — and eight independently pro- grammable sprites (24 x 21-pixel movable screen objects), which allow you more opportunities to create animation. The VlC-20 also has 16 colors and a graphics resolution of 176 x 184.
The Atari 600XL and 800XL each have 320 x 192 graphics resolutions, as well as 256 colors (16 colors with 16 luminance levels for each color). But the Ataris also have 11 different graphics modes, or varying com- binations of colors and pixel densities, which extend its graphics capabilities.
PC Pixels
IBM's PC and PCjr each have the same 320 x 200-pixel, four- color, high-resolution graphics mode, as well as the same 640 x 200, two-color mode. But the PCjr also has three other graphics modes that the PC doesn't: a 160 x 200, 16-color, medium- resolution mode; a 320 x 200, 16- color, high-resolution mode; and a 640 x 200, four-color, high- resolution mode.
Professional quality com- puter graphics systems may start
THE
Home Organizer'
' -SFRIFS
Comfortable a
Now your home computer can help you cook, keep your accounts, find an address or keep track of your record and book libraries— with first-class software specially tailored for the home environment.
The Home Organizer'" series includes a wide range of separate and individual programs for different activities like stamp collecting, personal banlang, or home photo and movie collections. Each one is pre-programmed with a "page" format planned out by experts to make it easy foryou to store and retrieve the information you'll want for your special activity. You don't have to program anything yourself. )ust load the disk and start feeding in your data.
If you're used to run-of-the-mill home computer software, the speed and simplicity of the Home Organizer'" series will surprise you. Each program is written entirely in "machine language ", the most basic computer code. So they search, sort and analyze your data with amazing speed.
The Home Organizer"" is fast enough to sort through your household belongings in seconds, yet so simple the children can use it to look up a phone number. Choose any or all program modules that fit your needs. They make ideal gifts, too!
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|
_J^ — ?to^ |
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A scene from the animated graphic adventure, Ring Quest, which was created with The Graphics Magician by Penguin.
at about a 600 x 500-pixel resolu- tion and go up from there. Color choices and luminance levels can go into the millions. Three- dimensional perspectives and complex simulations of actual processes^ such as flying an air- plane, are among the complex — and costly — features of some mainframe and mini computers.
A Child's Garden Of Graphics
Two programs by Scarborough Systems, Inc., make use of the computer's ability to create dynamic graphic images in a manner easy enough for a child to accomplish.
Picturewriter, by Dr. George Brackett, is an educational draw- ing program for children from 4 to 14 years of age, which Scar- borough markets for the Apple computers at $39.95 suggested retail price. Its origins, says Brackett, are in work he did teaching children about the Logo programming language. When he asked a little girl one day what she wanted to draw, she sug- gested a rainbow — not the easiest of images to produce via Logo.
32 COMPUni Mav198il
"So I began to think about what kind of program I would like to have that would make it easy for children to draw a rain- bow," he says. "And it was pretty clear that it had to have a pointing device, like a joystick, rather than a keyboard. I also felt it had to have fairly extensive editing capabilities."
As children use Picture- writer, they can learn about spa- tial and color relationships, the development of geometric pat- terns, and the basics of computer programming at the same time that they're creating colorful pictures. A selection of prepro- grammed works allow the child to alter the designs and colors as well.
Patterns For Appie, Commodore, And \BfA
Another program, which Scar- borough demonstrated at the recent Softcon show, is Pattern- maker, a drawing and pattern- creating program for children six years and older and for adults. The package is scheduled to be available in May for Apple com- puters and by August for Com- modore 64 and IBM machines.
at a suggested price of $39.95.
"Its educational value is that it gets children comfortable with symmetry, rotations, trans- formations, inversions, and so on," says Scarborough President Francis Pandolfi. "It makes it easy for them to use those con- cepts to make beautiful patterns. Symmetry is a very important concept in many areas of science, not to mention art. And the pro- gram's manual brings the child through all areas of art in which symmetry has been important."
As you'll quickly find out when studying what's available for microcomputer graphics, the products are coming fast and furious. Softron, Inc., for ex- ample, makes a Home Decorator program ($34.95 for Commodore 64; other versions planned soon) that teaches about colors, furni- ture layout, and decorating theory for your home and office. The package even lets you select carpeting, paint walls, and mgve furniture.
The Age Of Discovery
Other programs, like Access Software's Spritemaster ($34.95 for Commodore 64) and Avant- Garde's StarSprite series (for Apple computers), show you how to produce sprites for use in multicolor animation.
There are literally hundreds of other graphics programs cur- rently available. And there are numerous books and magazines which will teach you how to create your own colorful graphics.
"I think more and more people are discovering the graphics capabilities of com- puters," says Mark Pelczarski. "In the last couple of years, we've learned how to make soft- ware more easily understood. And with computers like the Commodore and the Atari really hitting the mass market, a lot of people who never would have dreamed of having a computer five years ago are learning about all the capabilities . " ©
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A lun way to dramatically increase typing speed and accuracy.
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And when it's time to shop for peripherals or J^ hardware, check COMPUTE! first. Our product J^ evaluations can save you money and costly mis-^^ takes. We'll even help you decide what to buy:^r Dot-matrix or daisy-wheel printer? Tape ^ storage or disk drive? What about ^^ modems? Memory expansion kits? Jr SUBSCRIBE What's new in joysticks, paddles ^ NOW AND and track balls? ^T SAVE UP TO
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Light Pens And Graphics Tablets:
New Ways To Communicate With Your Computer
Kathy Yakal, Editorial Assistant
You don't have to be an artist to use them. Or a three-year-old. Or a professional architect, engineer, or fabric designer. Light pens ami graphics tablets, along loith the software that drives them, are making computing easier for young children and adding neio dimensions in graphics for everyone.
Whether or not we admit it, we've probably all responded to our computer's SYNTAX ERROR message by typing "Syntax error? I typed it right!"
We may have jabbed a finger at the monitor to show our word processing program precisely which block of text we wanted moved and where we wanted it placed. Or maybe drawn a pic- ture of a spaceship and held it up to the screen to illustrate exactly what we wanted dis- played there after typing in a machine language game for the better part of a weekend.
The computer never seems to understand.
Interacting with a micro- computer can sometimes prove exasperating. You still have to talk to a computer in a language it understands. They don't yet respond to written or spoken Enghsh.
34 COMPUTE! May 1984
Animation Station, a graphics tablet designed by Suncom, offers a number of colors and textures for drawings like this.
ONE TOU
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Time was, Billy would do almost anything to duck his spelling homework.
But since Dad brought home Spellicopier™ by DesignWare™ Billy has become a spell- ing ace. As well as an ace chopper pilot.
Each week, in addition to the words already in the game, Billy types new spell- ing words and new sentences into the game. Then he takes command of his chopper and flies a mission through crowded skies and mountainous terrain to recover the words, letter by letter. And always in the right order.
So by the time Billy gets back to the base, he's one proud pilot. And one tough speller.
DESIGNWARE MAKES LEARNING COME ALIVE.
All DesignWare spelling programs
Commodore 64 is 3 tracemarlt of Commodort BmItouks Ltd. IBM PC and I3M PC Jr. are registered tr2demarks of interrriHiuna] Busbjcss Machines, Inc. .Apple h a refpstcred liademark of Apple Computer. !jic.
combine computer game fun with sound educational principles to help improve your youngster's spelling skills. That's why Spellicopier, for example, is consistently on the nation's best seller lists. You'll also want to keep an eye out for new math and science games.
All DesignWare programs run on these computers with disk drive: Apple® Atari,^ Commodore 64]" IBM PC and IBM PCjr. See your local software retailer or call DesignWare at (800) 572-7767 (in California 415-546-1866) for our free software catalog. You'll be delighted with the way your kids will learn with DesignWare.
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LEARNING COMES ALIVE.
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Today's
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bejganliere
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At Scholastic, we have something' no other educational software company has: 60 years' experience making learning fun for kids.
We began in the schoolrooms of the 20's with the first national news magazine written especially for young people, The Scholastic. Since then, our one magazine has grown into 37, and we've become the largest educational publisher of books and magazines in the English-speaking world.
Now we've put everything we've learned from five generations of school children into the most innovative family of educational software available today. Scholastic Wizware!"
Our experience makes Wizware different from all other educa- tional software, ft turns learning subjects like geography, writing and spelling into exciting adven- tures for your children. And be- cause every Wizware game is interactive, kids become deeply involved in what they're learning.
What's more, our experience has taught us the importance of teaching things most other educa- tional software leaves out. Like teamwork, imagination, critical thinking and problem solving. You'll find them all in Wizware.
But by far the most important result of our experience is that your children will thoroughly er\ioy learning with Wizware.
There are now Wizware programs for teaching everything fi'om crea- tive writmg to computer program- ming. Here are a few of the ways we bring learning into the Com- puter Age.
SpelldiverJ*'
ft's the most ingenious way ever devised for teaching spelling and improving reading skills. Deep beneath the sea lie giant words covered by a strange seaweed called lettermoss. Kids must face ferocious sharks and pesky flipper- nippers to remove the lettermoss and decipher the words.
Agent U.S.A!"
Agent U.S.A. turns geography into an exciting race to save the nation fi"om the ruthless P\izzbomb. Along with learning geography, children hone their problem-solving and reasoning abilities.
Story Tree:*'
Story Tree can bring out the Mai'k Twain in every child. Budding
authors create their own mystery and adventure stories. A remark- able feature lets them weave alter- nate choices into every turn of the plot, and challenges their ima^a- tions to the maximum.
Bannercatch™
Based on the classic game of Capture -the -Flag, this is the most sophisticated and fun strategy game for kids available today. Not only do players learn how to devise complex strategies, they also learn how to work together to solve difficult problems.
Scholastic Wizware. Our experi- ence makes all the difference.
Look for Wizware at your local computer store. Or contact Scho- lastic Inc., 730 Broadway, New York, NY 10003, 212-505-3000.
^^Scholastic Wip^are
Sjiifldhrr, Ai^nt iJ.S.A. and Barmercatch designed and deieluped try Turn Snydir h'odiictions, Inc. Story Tree deaiffjied and developed by Gforge Brackett.
Spelldiver, Agent US.A. and BaTineTcatchaiiifUu>ii jur Atari S00/1200/XL> CommodtjTe, Appie and IBM veraioni available soon. Story Tree available for AppU.
A Pointer To The Future
But graphics tablets and light pens bring us a step closer to easy communication by allowing infor- mation entry to bypass the keyboard. Like mice and joysticks and the keyboard itself, light pens and graphics tablets are input devices, peripherals through which you interact with your computer.
These pens and tablets do basically two things: draw and point. You can use them to select user options in menu-driven software and to create graphics.
A light pen is like a magic wand. It resembles a regular pen in size and shape, and has a cord that plugs into the computer. When you point it at the screen and activate it (either by pressing a switch on the pen itself or a key on the keyboard), it responds to whatever software you're running.
This picture urns created by using the draw and fill features ofFlexidraw ilnkiueU Systems).
Touch-Sensitive Input
A graphics tablet looks a little like an Etch-A- Sketch, though each manufacturer's is a little dif- ferent. Instead of pointing at the computer screen, you touch the surface of the tablet with your finger or a stylus.
Though light pens and graphics tablets are fairly new on the home computer scene, they've been used as design tools with larger computers for years. The technology is not brand-new.
Where's The Software?
The Edumate Light Pen, from Futurehouse, Inc., comes with introductory software that demon- strates the pen's features. If that's where it ended, the skeptics' claims that these tools are just gim- micks might be true.
But Futurehouse, along with other light pen
38 COMPUTE! May 1984
manufacturers and software publishers, is begin- ning to design software that can be used with a light pen. "The potential applications are enor- mous," says Byrne Elliot, president of Inkwell Systems, another pen manufacturer,
"Not just being able to point at a menu option you might want. They'd be great with even things like spreadsheets and word processors. Instead of learning a lot of control commands that can be very frustrating, you can move text and figures around quickly and easily."
Doing What Comes Naturally
If you've ever tried using spray paint to letter a sign or illustrate a big banner, you have an idea of what drawing with a light pen feels like. The stream of color sometimes comes out faster than you can control it.
Drawing on a graphics tablet is not quite so novel a technique to master. It's like drawing on a piece of paper with a pencil, or drawing pictures on a steamy windowpane with your finger. Using these pens or tablets is, however, intuitive, to a degree. "Among the first skills that everyone learns when they're young is drawing or writing," says Howard Leventhal, presi- dent of Suncom, manufacturers of Animation Station. "There are no other input devices that let someone do that in such a friendly way."
This may be why these new input devices are being so highly touted as educational tools. "There's a strong motivation for people to buy for educational purposes," says Leventhal.
Like Being A Kid Again
It's not hard to see why graphics tablets and light pens can open the world of computing for chil- dren. These peripherals don't require the hand- eye coordination or knowledge of letters and numbers that a keyboard does.
"Light pens are superb for education. They really expedite the learning process," says Elliot. "They're a good way to get around the intimida- tion of the keyboard. To respond to software using a keyboard, you have to type in a series of letters and numbers, then return. The light pen is gener- ally 10-15 times faster than that."
BobRanson, president of Chalkboard, agrees. "Graphics tablets allow the preliterate child to use a computer without having to deal with a keyboard," he says. "There are lots of two- and
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Real baseball is more than just hitting, pitching and fielding. It's also your favorite major league teams, the great stars of today and the Allstars of yesteryear. It's statistics and coaching, and it's managing your own game strategy. With the World's Greatest Baseball Game, you have it all. Pick your major league line-up using the actual player and team stats. Then watch the action unfold against
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One or two players; joystick controlled.
epyx
Strategy Games for the Action- Game Player
The Inside Story:
How Graphics Tablets And Light Pens Worl<
Ottis R. Cowper, Technical Editor
Many programmers find graphics tablets and light pens among the most mysterious of peripherals, but the principles of both are really fairly simple.
The graphics tablet is similar in operation to the more familiar game controller paddles. A paddle consists oi a variable resistor, a device which can vary the amount of electric current passing through it. For example, rotating the paddle all the way clockwise would allow full current to flow; turning it completely counterclockwise would cut off all current. A computer which accepts paddles must have circuitry which can read the varying current and provide a numeric reading which is proportional to the current, and hence to the position of the paddle knob. This is usually zero when the paddle is rotated all the way in one direction, 255 when the paddle is turned completely in the opposite direction. Joysticks for the Apple, Color Computer, and IBM function in a similar manner, with one resistor on the horizontal axis and another on the vertical.
Graphics Tablet Positions
In a graphics tablet, thin sheets of a special film are used in place of the variable resistors. When you press down on the film, a current flows, with the amount of resistance de- pending on where on the film you press. For example, if the film is set up to register hori- zontally from left to right, pressing on the left edge is equivalent to turning the paddle for minimum resistance, while pressing on the right edge is like turning the paddle for maximum resistance.
The working area of the tablet consists of two sheets of this film, one arranged to register horizontally and one arranged for
vertical measurements. The same circuitry used to read paddles (or Apple and IBM joy- sticks) can be used to read the tablet — the computer interprets each of the sheets as a paddle. What would normally be one paddle reading is the horizontal position of the point on the pad being pressed, while the other reading gives the vertical location.
One significance of graphics tablet de- sign is that you should be able to substitute paddles (or the joystick for Apple or IBM) in programs which call for the tablet. Con- versely, you might experiment with using the tablet in programs which call for paddles, although the tablet isn't likely to replace paddles for playing Pong or Breakout.
Holes Of Light
To understand how a light pen works, you must first understand how screen images are created. The chief element of any video dis- play device, television or monitor, is a cathode ray tube (CRT), a sealed glass funnel with an electron "gun" in the narrow end and a specially coated screen across the wide end. The gun shoots electron:; at the screen, leaving tiny bullet holes of light where the electrons strike the dark screen.
The shots are not random; they are care- fully targeted by powerful electromagnets, the big coils of wire around the throat of the CRT if you've ever looked inside a TV or monitor. Starting at the upper left corner of the screen, the gun is swept across at a con- stant speed. Shots are fired at the spots that need to be lit up to form part of an image. When the gun has swept all the way across to the right edge, firing is halted while it is aimed at the left edge again, slightly lower than on the first pass. Thus, the spray of
40 COMPUTE! May 1934
PUZZLEPANIC KEN USTON THINKS HE CAN DRIVE YOU CRAZY.
/
/
t^Jii^jl,
So you think there's no puzzle too tough for you and no video game you can't beat. Welcome to PuzzlePanic— The computer game that's sure to have you crying "uncle." Designed by Ken Uston, blackjack and arcade game player extra- ordinaire, PuzzlePanic takes you through 49 increasingly difficult screens based on seven different games of action, logic,
strategy and challenge. Compared to PuzzlePanic, Rubik's Cube'is child's play. So put on your thinking hat, grab your joystick, get ready for the contest of your life, and let Ken Uston drive you crazy.
One player; joystick controlled.
Epyx
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shots forms rows across the screen. Several rows are required to form a character. For example, alphanumeric characters for many computers are eight lines tall. To see this, type some spaces in inverse video. If you ■ look closely, you'll see that the reverse space character is a stack of thin, closely spaced lines rather than a solid block.
The drawing process must be repeated over and over because the bullet holes of light glow for only a fraction of a second be- fore fading away. In most computers, the screen is redrawn every '/«) second. If you had a very fast stopwatch that you started when the gun began firing at the upper left corner, you could read the elapsed time on the watch when the spray of electrons reached any particular point on the screen and, from this reading, determine how far you were from the starting position at the upper left.
This is the secret of light pen operation. In its simplest form, the pen is a plastic cylinder housing a phototransistor, a light- activated switch. {The phototransistor is what you see behind the lens at the end of the pen.) When the pen is held to the screen, the beam of electrons which light up the screen triggers the phototransistor, causing it to signal the computer that the beam has been detected. The computer must then check its video stopwatch to see how much time has elapsed since it started drawing the screen. It can then compute where on the screen the
pen is being held.
If the screen is being drav^fn many times a second, the pen will detect the spray of electrons each time the screen is drawn. Since the spots of light are so small, the pen may be triggered at a slightly different point each time. The readings you get from simple pens can thus be somewhat unsteady, especially for the horizontal location of the pen. Pro- grams written for simple pens usually require that you touch a key on the keyboard to tell the computer when you want the reading to be accepted.
More sophisticated (and hence more expensive) pens have additional circuitry which allows them to latch after triggering so that the readings do not change every time the screen is drawn. This means the readings will be much more stable, and that you will not need to use the keyboard. A switch in the pen tells it when to hold the current reading. In some, the switch is built into the nose of the pen so that you latch the reading by simply pressing the pen against the screen.
If you want to use a light pen or a graphics tablet with your own programs, keep in mind that they won't draw on the screen for you. Like a joystick or a set of paddles, the pen or pad provides only numeric readings. It's up to you to write the software which will decipher the input from the pen or tablet and then accomplish some- thing in your program.
three-year-olds using them,"
Beyond that, graphics tablets and light pens can attract adults as well. "People seem to enjoy being able to sit down and draw," says Ranson. "Graphics tablets meet a fundamental human need — the need to express oneself."
Light Pen Elbow?
The naysayers to these new communication tools complain about physical inconveniences. Your arm can get tired from holding the light pen. The cord can get tangled and caught under things. It can be confusing to look back and forth from the tablet to the screen.
"There is a spatial problem when you're writ- ing or drawing on the screen," says Ranson. "But I don't think it's major." Elliot argues that "Once familiarity sets in, you don't look at the tablet."
A more serious accusation is that thev're kids' stuff, that you can't do more than draw pictures of trees and bunnies and houses.
"Granted, tl^iey're great for kids," says Byrne
Elliot. "I know a lot of kids use Flexidraw for things like making valentines. But I also know of women who use it to design wallpaper and make dress patterns, and professionals who draw up plans for the interiors and exteriors of buildings with it. Graphics is becoming a lot more important to different kinds of people."
Input For The Future
Will a new input device come along thai will make pens and tablets or, for that inatter, keyboards obsolete? "Voice recognition is not as simple as some people think," says Chalkboard's Ranson. "Say you're a writer and want to sit down and dictate your work. I defy you to read everything you write all day. You'll lose your voice.
"Until we've reached the ultimate, there will be a lot more people exploring how to get into the computer other than QWERTY. We've been exist- ing with joysticks and keyboards for a long time now. There will always be room for more than one input device." q
42 COMPUTE! Moy1964
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If you've been having a hard time teaching your newly-adopted computer there's more to life than fun and games, you're not alone.
Now, you can introduce your Commodore 64™ to the Worl< Force: affordable, easy-to- use software and hardware that will unleash the power you always expected from your Commodore 64™, but thought you might never see.
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The Consultant"
{formerly Delphi's Oracle) is like a computerized filing cabinet with a brain. Organize files for recipes, albums, or the membership of your service club. Then search, sort, arrange and analyze your information with speed and flexibility that's simply astounding.
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A Portrait Of The Computer Artist
With Mil<e Newman
description of his computer art. He spoke with us recently about his development as a computer artist and the future of personal computer art.
Newman is quickly becoming one of the recognized masters of computer art. His work has been exhibited worldwide. Many of his computer paintings were featured in foseph Deken's recent book Computer Images: State of the Art.
I Newman, 29, is supervisor of Creative IServices for the DICOMED Corporation of Minneapolis, an international leader in pre- cision computer graphics. What started four years ago as a part-time experiment with DICOMED has since blossomed into a |: full-time commitment to computer
art. His paintings were created on a $130, 000 state-of-the-art computer design station.
COMPUTE! Books
GRAPHICS
COMPUTEI's Reference Guide To Commodore 64 Graphics
A complete tutoftal on Commodore 64 graphics. Noted Commodore author John Herlborn explains how to program sprites, multicolored screens, ani- mation, custom characters, and more. Beginners will like the step-by-step in- structions and ciear ex- ample programs. Advanced programmers can build up
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218 pages, paperback.
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■FOR KIDSi
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Contains 30 games written just for kids (although adults will enjoy them too). This book is an inexpensive source of educational soft- ware for children. The games are designed to teach math, geography, history, and other topics. Children learn while they're having fun. They will return to these games again and again.
240 pages, paperback.
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Continues in the tradition of the best-selling First Book ot Commodore 64 in presenting quality pro- grams and articles, many revised or never before published. There's some- thing for almost any 64 user: arcade and text ad- venture games, an impres- sive word processor, a program which adds 4 1 new BASIC commands, an electronic spreadsheet, sound and graphics tutorials, and information on saving, copying, and retrieving files.
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COtVSVIB'sftsrBco; -COMMODORE"
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m toTT^ co^lffi'.is^
COMPUTE!'! First Book Of Tl Games
Although this book is packed with ready-to-type- in games |29 in all), it is more than just a book of games. It is designed to teach game programming techniques. Introductory chapters explain the special features of the TI-99/4 and 99/4A, giving advice on coding techniques. Most i,^, games include an explana-
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211 pages, paperback.
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COMPUTEI's Second Book Of VIC
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Clear explanations of the 64 's sound and graphics capabilities. Includes many tutorials and example pro- grams: "MusicM3Ster,"a complete music synthe- sizer; "High-Resolution Sketchpad," an all- machine-language pro- gram for making computer art; and "Ultrafont Character Editor," one of the best character editors available.
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picking these icons, or picto- grams. For instance, if vou want to examine color and work with the color menu, you'd go to a magnifying glass icon that's perched over a picture of a rain- bow. And that means to examine color.
The design station has 640 pixels across on the screen and 480 down. VVe write everything down on the disk in very high resolution — 8000 lines. We can zoom into an area. We don't blow up the frame buffer as on other systems where you get great big pixels, big squares. We read it off a disk and redraw it so that we can actually address the resolution that the film re- corder [which turns the image into a color slide] is going to see. So, we have the addressa- bility of that high resolution, which is unique.
Then everything goes di- rectly onto the disk. We have
over 16 million colors that we can blend and use on the system. One of the things that we found out early on, and one of the things I was adamant about, was that we don't have lo con- sciously dump the data to disk. We have a continuous disk up- date system. But you can back yourself up in case you're going in a direction that you don't like and you want to get back to a previous state.
As an artist, you're gener- ally intensely working on some- thing and the last thing in the world you want to do is to re- member to save this or that.
COMPUTE!: What's the attrac- tion of computer art?
Newman: The first thing that attracted me was that it took only about ten minutes to un- derstand that this was just another tool, and that you could put a computer and art together.
Computer a tisl Mike Newman inspects his own digitized image.
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immediate shjpmem if in •j.tacit [Fnot. aliow 34 w€«ks for delivery If pcrsorysl check is sent allow addifloiuil 2 weeks. CS-1632 ships UPS (reighl coUecl from Oregon. CS-27^ shrps by InicM frcighl coikcl fromOregor^ Pnces subject to change. Shipment stihjed (o availabUilv
Both the CS- 1633 and CS-27';S ship unassembled in two canons Assembly requires onlya screwdnvcr.
hammer, and a few minutes of your lime
Choice in simulated woodgiain of warm golden oak or nch nalutitl wainm finish
The two slide-out shelves put the keyboard at the proper oper- ating height while allowing easy access to the disk drives. The bronze tempered glass door protecting the keyboard and disk drives simply tifts up and slides back out of the way during use.
Twist tabs on the back of the center pane! allow for neat con- cealed grouping of 'jvircs while a convenient storage shelf for books or other items lies below. The printer sits behind a fold down door that provides a work surface for papers or books while using the keyboard. The lift up top allows easy access to the top and rear of the printer. A slot in the printer sheif aliows for center as well as rear feed printers.
Behind the lower door are a (op shelf for paper, feeding the printer, and a bottom sheif to receive printer copy as well as additional storage. Stand fits same computers as the CS-1632 as well as the Appie i and II, IBM-PC. Franklin and many others. The cabinet dimensions overall: 39-1/2" high X 49" wide X 27" deep.
Keyboard shelf 20" deep x 26" wide. Disk drive shelf 15-34" deep X 26" wide. Top dielf for monitor 17" deep x 27" wide. Printer shelf 22" deep x 19" wide.
Some people think of the stereotype of a mathematically oriented artist, of which there are very, very few. There are some who do write their own programs and do artwork, but they are in a completely different ballpark. They are artists and scientists at the same time.
I figured if I could do this, then anybody could. It also at- tracted me that this was not a threat, because the computer wasn't going to do anything without me. It wasn't going to do anything terrific without somebody who knew about art.
COMPUTE!: What made you reach that conclusion?
Newman: When I saw the work that some of the programmers were doing. They weren't doing terrific work [artistically], al- though one of the programmers does really great graphics be- cause he also likes art.
It became clear very quickly what the benefits were: I could make a piece of art and experi- ment with it, begin to do things with it, and see that instead of just think about it. In conven- tional graphics you say "I won- der what this would look like if it were smaller, or turned a little
bit?" Whatever the changes — color, position, rotation, dupli- cation— instead of thinking about it, with the computer you can try it. You just do it.
It allows the artist to do real- time dreaming, giving you a much stronger sense of design. It's the same thing with color. The best thing I ever did was to take up watercolors because I had to understand what colors were doing when they were on top of one another, when they were mixed together. And the computer just enhances all that.
Now I blend colors in the same way using the computer, but I can see the artwork. After I have the artwork done, I can begin to play with colors and with shapes. It's Hke working on a painting and the paint never dries. You can still work with it, but it's more permanent than paint because it's digital on a magnetic medium. So, the per- manency is neat, but the flexibil- ity is just remarkable.
COMPUTE!: How do you an- swer critics who say that com- puter art is not a genuine art form?
Newman: I think that's a real misconception. People get the
Newman created the commercial graphics bar chart and surrounding artwork (far left) hy using an Apple lie and the DICOMED D38 and Imagina- tor design stations. "Geese," (top) an example of computer interpolation in which Escher-st\jle geese and a photo- graphic slide are transformed. The de- mands of commercial graphics (bottom) have helped to stretch the limits of com- puter art,
opinion that computer art is something done by a computer. In fact I'll read that occasionally: "This art was made by com- 'puter." Well, that whole concept is wrong. This art was made by a human using a computer. You don't say "This photograph was made by a camera." You usually give credit to the photographer, and it's the same thing with a computer. Not only that, but the person who wrote the program for the computer did a lot of crea- tive programming. There's creativity there, too.
If you look at the wide vari- ety of computer artwork, you
52 COMPimi May 1984
I
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Especially when you consider that the Abati LQ-20 is compatible with IBM, Apple, or any i other microcomputer you might own. j^H"
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At $479r it's easy to see why anyone looking for a great buy in letter-quality printers is looking at the Abati LQ-20. So should you. After all, you p don't have to be a tightwad to buy the Abati LQ-20. Just act like one. Call 1-800-447-4700.
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y'- -.'^■■■•r^J,^'^ '''^"^ ■
"Ed's First String Art."
can see that it's not just taking a picture and doing image pro- cessing, like distorting a picture. It's starting from nothing, a blank screen. Instead of a piece of paper, you have a video screen. And you work with shapes and colors and light and textures and all of the conventional things that we know about art. And you put these things together.
It has human emotional feelings built-in, just as every art form does. That's what makes it art. My work looks different from somebody else's work. That's because emotions are involved, and that's what com- puters don't have. Without the artist, it just sits there.
COMPUTE!: What influences have contributed to your com- puter artwork?
Newman: I take in as much in- formation from as many sources as possible. I like to think that
54 COMPUTE! Mav1984
my visual artwork is influenced by music as much as it is by other artists. I don't draw boundaries between dance and literary art and visual art. To me, it's all- encompassing. So I may have a visual depiction of a song, or music may have a certain effect on me that will give me a differ- ent sense of color for a particular design.
I am, however, influenced by other artists, I'd say the first computer artist — who was a computer artist without a com- puter— was M.C, Escher. This gets back to saying that computer art is not necessarily art made by computers. It's art made by hu- mans. If you look at Escher's work, it was made by the "com- puter" that he carried around with him. To me, he is the first computer artist. The difference is that he didn't have a computer.
Also, I'm very influenced by design technology — the revolu-
tionary. Buckminster Fuller, although he wasn't an artist in the conventic)nal sense, had a lot of influence on my work. And a host of a thousand musicians and other artists. [Laughs] In an unconscious way, I'm affected by everything that I see — Andy Warhol, James Wyeth — I enjoy everything.
COMPUTE!: What advice would you give those who want to get started in computer art?
Newman: The first thing you want to do to be a computer artist is to be a gooQ artist. You can learn the computer part, but it's hard to develop artistically. Whether you do it in art school or on your o-\vn, develop the artistic talent first.
I was not willing to become only a fine artist, because I was afraid that I v/ould wind up being a starving artist, and that's not what I wanted in life. Some
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Newman's "Metamorphosis" is another form of computer interpolation. Caterpillar becomes butterfly.
people feel so committed to the work they're doing that they'll take that. Those are conventional decisions you make about art, and they need to be made.
There are some schools in the United States and Canada now that are beginning to have computer graphics programs. They will give you a good over- view of the types of systems that are out there, and also give hands-on experience on the equipment so that they know what computer graphics is all about.
COMPUTE!: What are the limi- tations in computer art?
Newman: There's no medium that does everything. The more
56 COMPOni MOV 1984
painterly aspects of art are hard to simulate. In order to get the high resolution we have, we're based on what we call graphic primitive shapes. You tell the computer you want to make a line, and it knows you want to make a line. You tell it you want to make a perfectly round shape, and it expects you to tell it if you want a full round shape, how big it's going to be, and where it's going to start and stop.
There are other systems that work on a property of more painterly aspects, and these sys- tems are called paint systems. They're more like what you see on personal computers these days. That is, you say you want to make a brush that is this fat
and you want it to be this color, for instance.
The only problem is that you're just concerned with which little lights [pixels] are on and off, and it's hard to translate that into high resolution. You can't just take a display, even if it's a high-resolution display, and, say, double it and expect it to look better.
I do feel, however, that at some point this won't be a prob- lem. I still consider this medium to be in its very beginning stages. We're just coming out of the basement now. All I know is that as an ar iist who has access to computers, 1 have a lot to look forward to. And I expect many great things to occur. ©
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Plotting
Tim R. Colvin
Hozv many times have you seen beautiful three- dimensional grapliics in the ads for video monitors and printers? Now, with these easy-to-use programs, you can create three-dimensional images of your own. Ver- sions are included for the Commodore 64, Atari, Apple, IBM PC and PCjr.
These two programs, "Rectan" and "Spheri," will plot three-dimensional figures using informa- tion which you provide.
You don't really need to delve into the mathematics which produce the images. You can just fiddle with the examples given to produce many effective displays. Let's look at some graphic examples. First type in each program and SAVE it to tape or disk.
Then LOAD Rectan. To have Rectan draw a hyperbolic paraboloid, or "saddle function" (it resembles a riding saddle), replace line 790 with:
790 Z=X*X/4-Y*Y/9
and give the following inputs:
-2,2,-3,3,25,25,45
For another interesting design, use:
790 z=-l/(X*X+Y*Y+.5)
and give the following inputs:
-1,1,-1,1,20,20,45
The program will print SCREEN SCALING IN PROGRESS. The program is scaling the image to fit on the screen, which can require a lot of time. The rule is: The more complicated the description of the surface, the longer this step takes.
58 COMPUni May 1984
The Plotting Begins
When the previous step is completed, the screen will clear and turn cyan. The high-resolution plotting now begins. When the plot is finished, the color of the top left corner of the screen will change color. The program is locked in a loop so you can look at your creation. When you have finished looking at the display hold down RUN/ STOP and hit RESTORE.
A Spheri Demonstration
To see a torus {doughnut shape), type NEW to clear memory. Then LOAD Spheri, replace lines 820-840 with;
820 XT=(4+C1)*C2 830 YT=(4+C1)*S2 840 ZT=S1
and give the following inputs:
0,360,0,360,25,25,45
For a sphere, use:
820 XT=C1*C2 830 YT=C1*S2 840 ZT=S1
and give the following inputs:
0,360,0,180,15,15,45
An Illusion Of Depth
These programs use rectangular and spherical coor- dinate systems to create an illusion of depth in the screen image. You're probably familiar vvfith the X-Y coordinate system used to specify the location of a point on a flat surface. For example, in Figure 1 the point is located five units over on the X axis
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other TIMEWORKS MANAGE- MENT INFORMATION pro- grams into a fully integrated accounting system.
A Manual written in easy-to- understand, people-friendly English, abundantly iflustroted to provide further clarity and eliminate guesswork. Password Protection, to prevent unauthorized ac- cess to conlidential data. Suggested Retail List at $59.95 each.
Customer Support Plan
Timeworks Telephone Con- sulting Service is available to all users a! no charge to support your installation and ongoing operations.
For further details, contact your local Dealer or Timeworks, Inc. Choose from a host of Commodore 64 programs. Now at your favorite dealer. Or, contact Timeworks, RO. Box 321, Deeriield, IL 60015. 312-291-9200,
General Overview
Each system includes:
A Menu-driven program, sophisticated enough to provide complete Management and Product information, yet requires no prior computer or accounting knowledge to operate.
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A program which can be used by itself (stand- alone), or can be interfaced, one at a time, with
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and six units up on the Y axis. The point is said to be at location 5,6.
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Figure 1: l^^^^^H Two-Dimensional Rectangular Coordinates |
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This simple system works well for specifying the location of a point in a two-dimensional design on a flat surface, but for 3-D plotting you need a third coordinate.
Several coordinate systems are commonly used to plot three-dimensional surfaces. The par- ticular coordinate system you should use depends on the shape you want to draw. Any system can be used, but if you choose the right system, you can simplify your calculations considerably.
A Simple Solution
The easiest system to understand is just an exten- sion of the rectangular (X-Y) coordinates you are already familiar with. All you need to add is a third coordinate (Z) for the third dimension. For example, the point in Figure 2, below, is located five units out on the X axis, six units over on the Y axis, and four units up on the Z axis. The point is said to be at location 5,6,4.
z Figure 2: 1^ Three-Dimensional Rectangular Coordinates
X = 5 Y = 6 Z = 4
7L— , — ^ Y
A System For The Stars
On the other hand, if the design you wish to draw is roughly the shape of a sphere, you should use spherical coordinates. In that system, a point is de- scribed by two angles and a distance from the origin. For example, astronomers use spherical
60 COMPUTE! May 1984
coordinates to describe the position of a star rela- tive to the earth. The nzimuthal angle of the star, designated by the Greek letter theta ( 6 ). is the direction you must face to view the star. If north is taken to be zero degrees, then a star that lies due east has an azimuthal angle of 90 degrees. The elevation angle, designated by the Greek letter phi ( <}) ), specifies how much you must tilt your head back to look directly at the star. If the horizon is taken to be zero degrees, a star that is directly overhead has an elevation angle of 90 degrees. Finally, the radial distance, designated by the letter r, is the distance between the earth and the star.
Using spherical coordinates, the point shown in Figure 2 has an azimuthal angle of 50.2 degrees, an elevation angle of 33.7 degrees, and a radial distance of 8.77 units, as shown in Figure 3.
z Figures:
Spherical Coordinates
- -n 6 = 50.2° / ' (J) =33.7° I r = 8.77
1
Despite the fine graphics they produce, these programs have a couple of limitations. Screen pixels are taller than they are Vk'ide, which makes spheres look slightly less round than they should. Also, we see the surface as if ii were transparent and contour lines were drawn on it. A more ad- vanced program (such as those available commer- cially) would remove lines that we couldn't see if the surface were not transparent.
Program 1:Rectan— 64 version
Refer to the "Automatic Proofreader article before typing this program in.
100 REM * THREE-DIMENSIONAL SURFACES *
: rem 2 53 110 REM * IN RECTANGULAR COORDINATES *
irem 212 130 PRINT CHR$(147) : rem 15
140 PRINT "LOWER X LIMIT ";: INPUT Al
:rem 51 150 PRINT "UPPER X LIMIT " j ; INPUT Bl
:rem 66 160 PRINT "LOWER Y LIMIT ";sINPUT A2
:rem 65
%■ *^^
.■' ']
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Tvam statistical information into graphic format
GRAF 64 converts mathematical functions into graphical andysis on the Commodore 64. An ideal program for studying math. Define a function, set the limits of an axis, plot a graph and display the extreme points, intersection values, etc.
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The hyperbolic paraboloid resembles a saddle or a trough curving downward.
170
180 190 200
PRINT "UPPER Y LIMIT ";: INPUT B2
; rem 70
PRINT "SLICES IN X PRINT "SLICES IN Y
"; 1 INPUT Nirem HI "; tINPUT Mtrem 112
PRINT "OBSERVATION ANGLE
; : INPUT Q ;rem 108 "SCREEN SCALING IN PROGRESS"
irem 49 Q=Q*. 0174532925 i rem 209
CS=COS(Q) :rem 239
SI=SIN(Q) :rem 251
H1=(B1-A1)/319:H2=(B2-A2)/(N-1)
irem 254 H3=(B1-A1)/(M-1) ;H4=(B2-A2)/319:rem 2 H1=99999999:M2=M1:N1=-M1:N2=N1
: rem 167 FOR Y=A2 TO B2 STEP H2 FOR X=A1 TO Bl STEP HI
210 PRINT
220 230 240 250
260
270
280 290 300 310 320 330 340 350 360 370 380
GOSUB 610
NEXT X
NEXT Y
FOR X-Al TO Bl STEP H3
FOR Y=A2 TO B2 STEP H4
GOSUB 610
NEXT Y
NEXT X
:reni 87 I rem 84 rem 170 : rem 43 : rem 45 ;reni 81 ! rem 86 rem 175 I rem 49 :rem 49
390
400
410
420 430 440 450 460 470 480 490 500 510 520 530 540 550 560
D=ai92sPOKE 53272, PEEKC53272)OR8
:rem 218 POKE 53265, PEEK(53265)OR32 : rem 125 FOR I=D TO D+7999:POKE I,0:NEXT I
; rem 9 FOR 1=1024 TO 2023:POKE I,3:NEXT I
:rem 6 : rem 52 :rem 56 :rem 102 : rem 126 :rem 106 :rem 113 : rem 13 :rem 90 ! rem 78 :rem 181 : rem 46 ;rem 48 ! rem 84 :rem 89 : rem 186
Tl=(Nl-Ml)/2
T2=CN2-M2)/2
W=T1/T2
IF W<1. 60606061 THEN 480
XS=159:2S=159/W
GOTO 490
XS=99*W:ZS=99
FOR Y=A2 TO B2 STEP H2
FOR X=A1 TO Bl STEP HI
GOSUB 690
NEXT X
NEXT Y
FOR X=A1 TO Bl
FOR Y=A2 TO B2
GOSUB 690
570 NEXT Y
580 NEXT X
590 POKE 1024,16
600 GOTO 600
610 GOSUB 790
620 XT=X-Y*CS
630 ZT=Z-Y*SI
640 IF XT>N1 THEN N1=XT
650 IF XT<M1 THEN Ml=XT
660 IF ZT>N2 THEN N2=ZT
670 IF ZT<M2 THEN M2=ZT
680 RETURN
690 GOSUB 790
700 XT=160+INT(XS*CX-Y*CS-N1+T1)
710 ZT=100-INT(ZS*(2-Y*SI-N2+T2)
720 R0=INTCZT/8)
730 CH=INT(XT/8)
740 LN=(ZT)AND7
750 BI=7-( (XT)AND7)
760 BY=D+320*RO++8*CH+LN
770 POKE BY,PEEK(BY)0R(2TBI)
780 RETURN
790 Z=X*X/4-Y*Y/9
800 RETURN
:rem 52
: rem 52
; rem 39
: rem 101
:rem 183
: rem 31
: rem 42
; rem 41
5 rem 38
: rem 49
;rem 46
: rem 126
:rem 191
/Tl)
srem 82 /T2)
srem 94 : rem 200 : rem 177 :rem 123 5 rem 32 I rem 76 ;rem 178 srem 127 :rem 229 irem 120
160 PRINT "LOWER PHI LIMIT
170 PRINT "UPPER PHI LIMIT
180 PRINT "SLICES IN THETA
190 PRINT "SLICES IN PHI ";
STEP H3 STEP H4
Program 2: Spherl— 64 version
Refer to the "Automatic Proofreader" article before lyping ttiis program in.
100 REM * THREE -DI MENS I ONJ\L SURFACES *
: rem 253
110 REM *{2 SPACES} IN SPHERICAL COORDINAT
ES{2 SPACES]* :rem 55
130 PRINT CHR$(147) : rem 15
140 PRINT "LOWER THETA LIMIT "r:INPUT Al
1 rem 91 150 PRINT "UPPER THETA LIMIT ";:INPUT Bl
trem 96 " r : INPUT A2
:rem 201 " ; : INPUT B2
trem 206 "; : INPUT N
:rem 141 s INPUT M
trem 248 200 PRINT "OBSERVATION ANGLE "; s INPUT Q
trem 108 210 PRINT "SCREEN SCALING IN PROGRESS"
irem 49 220 U=. 0174532925 trem 90
230 Q=Q*U srem 243
240 CS=COS(Q) srem 240
250 SI=S1N(Q) trem 252
260 H1=(B1-A1)/319:H2=(B2-A2)/(N-1)
irem 255 270 H3=(B1-A1)/(M-1) tH4=(B2-A2)/319:rem 3 280 M1=99999999:M2=M1;N1=-M1:N2=N1
trem 160 290 FOR Y=A2 TO B2 STEP H2 trem 88 300 FOR X=A1 TO Bl STEP HI srem 76 310 GOSUB 620 trem 172
320 NEXT X trem 44
330 NEXT Y trem 46
340 FOR X=A1 TO Bl STEP H3 trem 82 350 FOR Y=A2 TO B2 STEP H4 trem 87 360 GOSUB 620 trem 177
370 NEXT y trem 50
380 NEXT X trem 50
62 COMPUTCI Way1<J84
V
^.
THE ULTIMATE FtlGHT EXPERIENCE
A- -/
:.:^^:^<PC'-
OVER TWO DOZEN GAME SCREENS !
Put yourself in the pilot's seat of an advanced AGX hypersonic fighter! The year is 2036 and the time is now. Your mission is to destroy COMPUTER COIMTROL, a renegade CPU out to take over the untuerse. You'll fly in low over awe-inspiring scenery whose beauty just might be your end. Guarding the approach to its fortress is an endless array of computer controlled FLAK batteries. They always seem to know where you are, where you're going and where you'll be. You fire, evade, fire again ... Your hand tightens around the flight control, you push harder on the fire button, the tension builds ... Can you take it? Will you survive the FLAK?
BY: Y. Lempereur and A. Marsily
SEE YOUR DEALER
or write or call for more informa- tion. If unavailable from your local dealer, send S34.95 plus S2.00 for shipping. Foreign orders add S 5.00 Mastercard /Visa accepted.
ainsoFT
286'11B Canwood St.
Agoura, CA 91301
818-991-6540
TELEX 181161
Available now for:
APPLE ll/IIE & ATARI 800 [XL]/ 1200 ■■ 48K,
COMMODORE 64 on DISK 534.95
3 Car.'ro3o-e 6i are vsxwai^s of Apple Computer. Alan, ana CsTimodD'e mi . inc resbectwely.
The Mathematics Of 3-D Plotting
"Rectan" plots surfaces using rectangular coordinates (x,y,z). The values for x and y are specified; the value of z is then given by z = f(x,y) for some function f.
To use Rectan, specify the function f{x,y) in line 790. For example, z = x*x/4-y*y/9 defines a hyperbolic paraboloid.
"Spheri" plots surfaces using spherical coordinates. This method describes a point on the surface using three parameters: radial distance from the origin, r; azimuthal angle, theta ( 9 ); and elevation angle, phi ( <^).
To use Spheri, specify x,y, and z (called XT,YT, and ZT in lines 82&-840) as functions of r, theta, and phi in lines 820-840.
Parameters And Slices
Both programs are structured the same. You specify parameter ranges. In Rectan these are for x and y; in Spheri, for 0 and <l>.
Next enter the number of slices for the parameters. Each slice corresponds to a con- tour line on the surface, A contour line is where one of the parameters is held constant.
Finally, you specify an observation angle. This is the angle which allows you to see a three-dimensional surface on a two- dimensional video screen. The most com- monly used angle is 45 degrees.
If you'd like any technical information, or if you have a particular surface in mind but don't know how to write an equation for it, please write to:
Tim R. Colviij 1414 San Remo Dr. Pacific Palisades, CA 90272
|
390 |
D=8192!POKE 53272, PEEK(53272)OR8 |
|
|
:rem 219 |
||
|
400 |
POKE 53265, PEEK(53265)OR32 |
:rem 117 |
|
410 |
FOR I=D TO D+7999:POKE 1,0: |
NEXT I :rem 10 |
|
420 |
FOR 1=1024 TO 2023:POKE 1,3 |
:NEXT I s rem 7 |
|
430 |
Tl=(Nl-Ml)/2 |
I rem 5 3 |
|
440 |
T2=(N2-M2)/2 |
:rem 57 |
|
450 |
W=T1/T2 |
srem 103 |
|
460 |
IF W<1. 60606061 THEN 490 |
;rem 128 |
|
470 |
XS=159:ZS=159/W |
srem 107 |
|
480 |
GOTO 500 |
I rem 106 |
|
490 |
XS=99*W:ZS=99 |
srem 14 |
|
500 |
FOR Y=A2 TO B2 STEP H2 |
srem 82 |
|
510 |
FOR X=A1 TO Bl STEP HI |
srem 79 |
|
520 |
GOSUB 700 |
srem 174 |
530 NEXT X
540 NEXT Y
550 FOR X=A1 TO 31 STEP H3
560 FOR Y=A2 TO B2 STEP H4
570 GOSUB 700
580 NEXT Y
590 NEXT X
600 POKE 1024,16
610 GOTO 610
620 GOSUB 800
630 XT=XT-YT*CS
640 ZT=ZT-YT*SI
650 IF XT>N1 THEN N1=XT
660 IF XT<M1 THEN M1=XT
670 IF ZT>N2 THEN N2=ZT
680 IF ZT<M2 THEN M2=ZT
690 RETURN
700 GOSUB 800
710 XT=160+INT(XS*(XT-YT*CS-N1+T1
720 ZT=100-INT(ZS*CZT-YT*SI-N2+T2
730 R0=INT{ZT/8)
740 CH=INT{XT/8)
7 50 LN=(ZT)AND7
760 BI=7-( (XT)AND7)
770 BY=D+320*RO+8*CH+LN
780 POKE BY,PEEK(BY)OR(2t3I)
790 RETURN
800 XA=X*UsCl=COS(XA) :S1=3IN(XA)
810 YA=Y*U:C2=C0S(YA) :S2=SIN(YA)
820 XT=(4+C1)*C2
830 YT=(4+C1)*S2
840 2T=S1
850 RETURN
Program 3: Recton-^tari version
s rem 47
: rem 49
; rem 85
; rem 90
srem 179
srem 53
srem 53
srem 31
srem 103
srem 176
srem 200
srem 211
s rem 42
:rem 39
srem 50
s rem 47
I rem 127
s rem 175
)/Tl)
s rem 2 51
)/T2)
5 rem 7
srem 201
srem 178
srem 124
srem 33
srem 34
srem 179
srem 128
srem 206
srem 213
s rem 70
srem 88
srem 11
srem 125
Refer to the "Automatic Proofreader" orticle before typirig this program in.
BF OP PE PD
PI
CE
cc
130 140
150 160 170 1B0 190 fiO 200 OS 210 10 215 PC 220 DP 230 PL 240 PO 250 AC 260 ilH 270 FH 2B0 FE 290 VX 300 CI 3 1 0 CN 320 FB 330 FS 340 t;p 350 DB 360 DB 370 CE 380 P6 390 QL 400 CI 4 10 EK 4 1 5 OE 420
GRAPHICS ? "LOWER "UPPER "LOWER "UPPER "SLICES "SLICES "OBSERV "SCREEN U=0. 01745 Q = Q«U CS=CDS (D) SI=SIN (Q) Hi= (Bl-Al H3= (Bl-Al Ml=999999 FDR Y=A2 FOR X=A1 GOSUB 610 NEXT X NEXT Y FOR X=A1 FOR Y=A2 GOSUB 610 NEXT Y NEXT X GRAPHICS SETCOLQR SETCOLOR SETCOLOR COLOR 1 Tl= <N1-M1
LIM
LIM
LIM
LIM
IN X
IN Y
ATION
SCAL
32925
) /319 ) / (M- 99s M2 TO B2 TO Bl
IT" ; 5 INPUT Al
IT";: INPUT Bl
IT" ; : INPUT A2
IT" ;s INPUT B2 " ; : INPUT N "; : INPUT M ANGLE"; : INPUT
Q
ING IN PROGRESS"
:H2= (B2-A2) / <N-1) 1) ; H4= (B2-A2) /319 = M:1 :Nl = ~Mi s N2 = N1
STEP H2
STEP HI
TO TO
Bl B2
STEP STEP
H3 H4
B
2,0,0
4,0,0
1,9, i:
) /2
64 COMPUH! May1984
you want to stay ahead of the personal computing
solution ...
A-elcome to COMPUTE!' s PC & PCjr!
is exciting new magazine from COMPUTE! takes
J inside the PC and the incredible new PCjr to bring
J inside information you'll find nowhere else.
fou'll discover how to get the most computer power f your money. At home. At school. At work. With easy- run programs. Challenging
)jects for advanced users.
|ind new sound and graphics
Jlications. Plus some of the
l>st exciting computer
ictions outside of the top-
'ret research labs! lA'e'll help you decide what buy. With independent
iluations of hardware,
ftware and peripherals.
imprehensive reviews of products as they're intro-
jed. Hard-nosed evalua- ^- n.s of each machine's •^■^angths and weaknesses.
OOMPUTEI's PC & PCjr
From the publishers of COMPUTE!
■|H|HB|IT
■1 keep you on the leading
ge of personal computing
e no other publication can.
re are some of the features
u can took forward to:
f>\come to the PCjr! A com-
J 'te introduction to IBM's
i west personal computer,
# d a fascinating peek at the
#Ji38 microprocessor - the
m ^y-but-talented brain of the
I ''
M signing PCjr — The Inside
A^^try. PCjr's creators tell how fl^^Ky designed the new com- ^^^^■ter - from original planning
hai^tierI Swings
OFI-liR
Announcing
the magazine
that takes you
Inside the IBM
PC and the PCjr.
COMPUTES's
DESIGNING THE PCjr: The Inside Story
*
to trade-offs to ultimate success.
Telecomputing with Your IBM. How to link up with dis- tant computers over ordinary phone lines, access infor- mation services, even do office work at home with your own machine!
Music and Graphics. How to play songs and create sound effects with your PC or PCjr. Programs to gener- ate impressive hi-res graphics and computer animation.
Your First Hour with an IBM.
How to avoid those opening night jitters and get your com- puter up and running fast!
Financial Analysis. Ready-to- run programs to help you make intelligent investments. PC vs. PCjr. Which one is right for you? COMPUTE!' s PC & PCjr helps you decide!
PLUS: Programming the func- tion keys to suit you. Speeding up BASIC without resorting to machine language. Tape, disk, or hard disk? Buyer's guides. How to take advantage of free public-domain software. Computing activities for the whole family Reviews. Games. Educational programs for children. And much, much more!
Subscribe right now and you can enjoy special Charter Sub- scriber Savings on COM- PUTERS PC & PCjr -just $24 for the first 12 big issues. That's 339?^ off the cover price!
To start receiving COM- PUTEI's PC & PCjr, just mail the postpaid card in this issue or the coupon below today
\\
OR CALL TOLL FREE i'800-334-0868
magazrne
f
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i \ k\ti;r
my Chart IT Subscrip- tion to rOV/PlT^/^ PC & PCjr. 1 pay just S24 for tho first 12 ^ issue-s— a 31!% saving off the cover price. What's more, I reserv* the risht to cancel at any time for a full pro-rata refund.
MAIL TO:
COMPUTE'S PC&PCjr
P.O. Box 974, Farminsfdaie.NYma?
J Payrncnt enclosed [ ] Bill me Charite
[ ] VISA [ ] MasterCard
/WME^JJJJJ J J J J J J J J J J J J J 11 ,W*.„E,„r.,» 'JJJJJJJJJJJJJJJJJ-
JJJJJJJJ JJ J J J J J J J '. iJJJJjJJJJJJJJJJJ
.\cct. No. L
Kxp. Date
BI 430 6G 440 HD 450 6K 4 60 H6 470 flj 4 80 FK 490 EO 500 LF 510 CO 520 Dfi 530 F£ 540 FJ 550 LK 560 CE 570 SE 580 KF 570 LH il0 BP 620 QK 630 CJ 640 C6 650 DB 660 Ca 670 HO 680 LP 690 FC 700
BF 710
FO 720
Ht: 7 30
LE 790
HI 800
T2 =
W = T
IF
XS =
GOT
XS =
FDR
FOR
GOS
NEX
NEX
FOR
FOR
GOS
NEX
NEX
END
GOS
XT =
ZT =
IF
IF
IF
IF
RET
GOS
XT =
)
ZT =
PLO
RET
Z = -
RET
(N2
1/T
W< 1
159
0 4
79*
Y =
X =
UB
T X
T Y
X =
Y-
UB
T Y
T X
UB
X-Y
Z-Y
XT>
XT<
ZT>
ZT<
URN
UB
160
-M2) /2
2
.60606061 THEN 480
: ZS=159/W
90
W: ZS=79
A2 TO B2 STEP H2
Al TO Bl STEP HI
690
Al TO Bl STEP H3 A2 TO B2 STEP H4 690
790
«CS
«SI
NI THEN N1=XT
Ml THEN M1=XT
N2 THEN N2=ZT
M2 THEN M2=2T
790 +INT(XS»(X-Y*CS-N1+T1>/T1
B0-INT (ZB« CZ-Y«SI-N2 + T2) /T2)
T XT, ZT
URN
1 / ( X«X+Y«Y + 0.5)
URN
Program 4: Spheri^Atari Version
Refer to the "Automatic Proofreader" article before t/ping this program in,
BF AN BC HL lA DP
130 140 150 160 170 180 190 BO 200 DD 210 10 215 PC 220 OP 230
a 240
PO 250 AC 2 60 KH 270 FH 2e0 FE 290
KK 300 CL 3 10 CN 320 fB 330 FB 340
r,p 350
DB 360
DB 370
CE 360
PB 390
DL 400
Ci 410
EK 4 15
DE 420
DI 430
66 440
KQ 450
&. 460
ERA
PHIC LOWE UPPE LOWE UPPE SLIC SLIC 0B5E SCRE . 017 «U
COS ( SIN ( (Bl- (Bl- 9999 Y = A X=A
S R R R R EB
0
THETA LI THETA LI PHI LIMI PHI LIMI IN THET
ES IN PHI" RVATION AN EN SCALING 4532925
Q)
Q)
Al ) /319;H2
Al ) / (M-1 ) :
9999:M2=M1
2 TO B2 BT
1 TO Bl ST
7
? 7 •7 7
U = 0 Q = Q CS = SI = Hl = H3 = Ml = FOR FDR
GOSUB 610
NEXT X
NEXT Y
FOR X=A1 TO Bl STEP
FDR Y=A2 TD B2 STEP
GOSUB 610
NEXT Y
NEXT X
GRAPHICS B
SETCOLDR 2,0,0
SETCOLDR 4,0,0
SETCOLDR 1,9,15
COLOR 1
Tl= (Nl-Ml ) /2
T2= (N2-M2J /2
W=T1 /T2
IF W<1. 60606061
XS=i59: ZS=159/W
MIT";:INPUT Al MIT" ; : INPUT Bl T"; : INPUT A2 T" ; : INPUT B2 A" ; : INPUT N ; : INPUT M GLE";: INPUT D IN PROGRESS"
= <B2-A2) / <N-1) H4= (B2-A2) /319 :N1=-M1 :N2=N1 EP H2 EP HI
H3 H4
The "Rectan" program was used to create this "fish net."
KB 470 AJ 480 FK 490 EO 500 LF 510 CD 520 DA 530 FE 540 FJ 550 LK 560 DE S70 DE 580 HP 590 LK 610 HH 620 NC 630 CJ 640 CS 650 DB 6 60 CO 670 HO 690 LP 690 P>. 700
NK 710
FO 720 W. 730 KS 7 90 HE 800 E6 8 20 PI 830 AL 840 HN 850
GOTO XS = 79 FOR Y FDR X GOSUB NEXT NEXT FDR X FDR Y GOSUB NEXT NEXT END GOSUB XT=XT ZT = ZT IF XT IF XT IF ?T IF ZT RETUR GOSUB XT=16 Tl ) ZT = a0 2)
PLOT RETUR XA=X» YA = Y» XT= (4 YT= (4 ZT = S1 RETUR
ZS = 79
TO B2 STEP H2 TO Bl STEP HI 0
TO Bl STEP H3 TO B2 STEP H4
490 «U: = A2
= A1 69
X
Y
= A1
= A2 69
Y
X
790 -YT«CS -YT*SI
>N1 THEN N1=XT <M1 THEN M1=XT >N2 THEN N2=ZT <M2 THEN M2=ZT N
790 0+INT <XS« (XT-YT»CS-
Nl+Tl ) /
-INT (ZS« ( ZT-YT*SI-N2+T2) /T
XT, ZT
N
U:C1=CDS(XA) :S1=SIN(XA)
U:C2=CDS(YA) :S2=SIN ( YA>
+C1 ) *C2
+C1 ) »S2
N
Program 5: Rectan— PC/PCJr Version
THEN 480
|
100 |
SCREEN |
1 0,0,0:CLS |
|
140 |
INPUT |
"Lower X limit ";A1 |
|
150 |
INPUT |
"Upper X limit ";B1 |
|
160 |
INPUT |
"Lower Y limit " ; A2 |
|
170 |
INPUT |
"Upper Y limit " ; B2 |
|
180 |
INPUT |
"Slices in X ";N |
|
190 |
INPUT |
"Slices in Y ";M |
|
200 |
INPUT |
"Observation angle ";D |
|
210 |
|
"Screen scaling in progress |
|
220 |
U=. 0174532925*: D=Q»U |
|
|
230 |
CS=COS(Q) |
|
|
240 |
SI=SIN<Q) |
|
|
250 |
H1=(B1 |
-Al ) /639:H2= (B2-A2) / <N-1) |
66 COMPUTE) May 1984
^ uumpon 10 monsters, 64 screens and
$10,000
witiiF^Joe.
A Mutated Wonderwhisk whisks by. ^^i^F Keep bouncing Joe to original
Keep bouncing Joe to original music on realistic 3-dimensional cylinders. All the characters in this rollicking ^ game are also 3-dimensional and
The Spinninglbp almost topples him!
Close. But Pogojoe bounces back. Bouncing from cylinder to cylin- der, screen to screen,
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 ^^^H^^^^^ Simply tell us what magic word appears
on to the next. H^BHBH ^^^ A^ aiter Pogo Joe's tenHh
The more screens ^^^X"tT« S^^^i^^S^^^, screea If your name
you complete, the tV**'"-**'Vj i^^S^^^^^ is drawn from
nastier the monsters BAji^^'" HH ^^^^^^^M^^ among the correct
you face, and the faster ^^1 "^-^H ^^^^^^i^^^ll answers you'll win
they attack. ^^UU^^V I^^kKS^S^ $10,000!
Press the fire button! Jimip two cylin- ders to safety. Hop into a transport tube, and dien whoosh! Pogo Joe appears across the screen. Jump on an
escaping monster. Blam! Ifs gone in a flash! Only to reappear out of thin air
No purchase is necessary You'll find entry forms at any store that sells Screenplay'' games.
But if you don't win you can't lose. Pogo Joe''' is so much fun you'll jump for joy no matter what _!?«"««
■screenplay"
Box 3558.Chapel Hill. NC 27514 800-334-5470
Pogojoe in 48-64Kon the Atari and Commodore 64. See your local software dealer.
|
260 |
H3=(B1-A1) /(M-1) !H4=(B2-A2)/639 |
|
270 |
Ml=99999999#: M2=M1 : N1=-M1 : N2=N1 |
|
2BO |
FDR Y=A2 TO B2 STEP H2 |
|
290 |
FOR X=A1 TO Bl STEP HI |
|
300 |
GDSUB 610 |
|
310 |
NEXT X |
|
320 |
NEXT Y |
|
330 |
FOR X=A1 TO Bl STEP H3 |
|
340 |
FDR Y=A2 TO B2 STEP H4 |
|
350 |
eOSUB 610 |
|
360 |
NEXT Y |
|
370 |
NEXT X |
|
3B0 |
SCREEN 2, 1 |
|
420 |
T1=(N1-Mi) /2 |
|
430 |
T2=(N2-M2) /2 |
|
440 |
W=T1/T2 |
|
450 |
IF W<3. 212121211* THEN 480 |
|
460 |
XS=319:ZS=319/W |
|
470 |
GOTO 490 |
|
4B0 |
XS=199tW; ZS=99 |
|
490 |
FDR Y=A2 TO B2 STEP H2 |
|
500 |
FOR X=A1 TO Bl STEP HI |
|
510 |
GDSUB 690 |
|
520 |
NEXT X |
|
530 |
NEXT Y |
|
540 |
FOR X=A1 TO Bl STEP H3 |
|
550 |
FOR Y=A2 TD B2 STEP H4 |
|
560 |
GDSUB 690 |
|
570 |
NEXT Y |
|
530 |
NEXT X |
|
590 |
GOTO 590 |
|
610 |
GOSUB 790 |
|
620 |
XT=X-Y«CB |
|
630 |
ZT=Z-Y»SI |
|
640 |
IF XT>N1 THEN N1=XT |
|
650 |
IF XT<M1 THEN M1=XT |
|
660 |
IF ZT>N2 THEN N2=ZT |
|
670 |
IF ZT<M2 THEN H2=ZT |
|
680 |
RETURN |
|
690 |
GOSUB 790 |
|
700 |
XT=320+INT(XS«(X-Y*CS-N1+T1)/T1) |
|
710 |
ZT=100-INT(ZS« (Z-Y*SI-N2+T2) /T2> |
|
720 |
PSET (XT,ZT) |
|
730 |
RETURN |
|
790 |
Z = X+Y |
|
BOO |
RETURN |
|
Pro |
gram 6: Spheri— PC/PCjr version |
|
100 |
SCREEN 0,0,0:CLS |
|
110 |
KEY OFF |
|
140 |
INPUT "Lower Theta limit " ; Al |
|
150 |
INPUT "Upper Theta limit " ; Bl |
|
160 |
INPUT "Lower Phi limit " ; A2 |
|
170 |
INPUT "Upper Phi limit " ; B2 |
|
ISO |
INPUT "Slices in Theta ";N |
|
190 |
INPUT "Slices in Phi "iM |
|
200 |
INPUT "DbBervation angle ";D |
|
210 |
PRINT "Screen scaling in progres |
|
220 |
U=. 0174532925#: Q=Q*U |
|
230 |
CS=COS(Q) |
|
240 |
SI=SIN(Q) |
|
250 |
H1=(B1-A1)/639:H2=(B2~A2) /(N-U |
|
260 |
H3= (Bl-Al) / (M-n ■- H4= CB2-A2) /639 |
|
270 |
H 1 =99799999^ : H2=M 1 : N 1 =-M 1 : N2=N 1 |
|
280 |
FDR Y=h2 TO B2 STEP H2 |
|
290 |
FOR X=A1 TO Bl STEP HI |
|
300 |
GOSUB 610 |
|
310 |
NEXT X |
|
320 |
NEXT Y |
|
330 |
FOR X=A1 TO Bl STEP H3 |
|
340 |
FOR Y=A2 TO B2 STEP H4 |
|
350 |
GDSUB 610 |
|
360 |
NEXT Y |
|
370 |
NEXT X |
|
380 |
SCREEN 2, 1 |
|
420 |
Tl=(Nl-Ml)/2 |
|
430 |
T2=(N2-M2)/2 |
|
440 |
W=T1/T2 |
|
450 |
IF W<3. 21212121* THEN 480 |
|
460 |
XS=319:ZS=319/W |
|
470 |
GOTO 490 |
|
480 |
XS=199«W:ZS=99 |
|
490 |
FOR Y=A2 TO B2 STEP H2 |
|
500 |
FOR X=A1 TD Bl STEP HI |
|
510 |
GOSUB 690 |
|
520 |
NEXT X |
|
530 |
NEXT Y |
|
540 |
FOR X=A1 TO Bl STEP H3 |
|
550 |
FDR Y=A2 TO B2 STEP H4 |
|
560 |
GOSUB 690 |
|
570 |
NEXT Y |
|
580 |
NEXT X |
|
590 |
GOTO 590 |
|
610 |
GDSUB 790 |
|
620 |
XT=XT-YTtCS |
|
630 |
ZT=ZT-YT«SI |
|
640 |
IF XT>N1 THEN N1=XT |
|
650 |
IF XT<M1 THEN M1=XT |
|
660 |
IF ZT>N2 THEN N2=ZT |
|
670 |
IF ZT<M2 THEN M2=ZT |
|
680 |
RETURN |
|
690 |
GOSUB 790 |
|
700 |
XT=320+INT(XS«(XT-YT*CS-N1+T1)/T1) |
|
710 |
ZT=100-INT(ZS* (ZT-YT«SI-N2+T2) /T2) |
|
720 |
PSET <XT,ZT) |
|
730 |
RETURN |
|
790 |
REM The -function |
|
800 |
XA=X*U:C1=CDS(XA) :Sl=SIN(Xfi) |
|
810 |
YA=Y«U:C2=C0S<YA) :S2=SIN(YA> |
|
820 |
XT=(4+C1)«C2 |
|
830 |
YT= (4+Cl) «S2 |
|
840 |
ZT=S1 |
|
850 |
RETURN |
Program 7: Rectan^Appl« version
100 HC0L0R= 3
130 HOME
140 INPUT "LOWER X LIMITi"|Al
150 INPUT "UPPER X LIMIT: ";B1
160 INPUT "LOWER Y LIMITi";A2
170 INPUT "UPPER Y LIMIT: "fB2
180 INPUT "SLICES IN X:";N
190 INPUT "SLICES IN Y3";M
200 INPUT "OBSERVATIDN ANGLE: ";Q
210 PRINT "SCREEN SCALING IN PROBRESS"
215 U = .0174532925
220 Q = Q * U
230 CS = CDS <G)
240 SI = SIN (Q)
250 HI = (Bl - ftl> / 279: H2 = <B2 - A2> / CN
- 1) 260 H3 » CBl - fii) / CM - 1):H4 = CB2 - A2> /
279 270 Ml - 9999999: M2 - MlsNl - - Ml!N2 2B0 FOR Y = A2 TO B2 STEP H2 290 FDR X = Al TO Bl STEP HI 300 BOSUB 610 310 NEXT 320 NEXT
Nl
68 COMPUn! May 1984
NOW FOR YOUR »PLE OR COMMODORE
Cosmic 'ninnels
Mr. Robot
Go ahead. Take one for a spin. But be pre- pared. These games will challenge you like no others. Incredible arcade animation. Never-ending action. And magical music. Your eyes won't believe your ears. Are you up to it? Are you ready to test yourself against the best that DATAMOST has to offer? Go ahead. Take one for a spin.
DATAMOSl
The most out of our mindsl
Datamost, lnc„ 20660 Nordhoff SL. Chatswarth. CA 9131 i , (213) 709-1202
•Atari te a trademark of Atari Computer. 'Apple is a trademark of Apple Computer.
'Commodore 64 Is a tradeinark of Commodore Business Machines, Inc.
"3-D Plotting" can create spectacular pictures such as this torus or "doughnut."
This sphere was drawn iisin^ the "Sphcri" program.
|
330 |
FOR X |
- Al TO |
Bl STEP H3 |
|
340 |
FOR Y |
- A2 TO |
B2 STEP H4 |
|
350 |
GOSUB |
610 |
|
|
360 |
NEXT |
||
|
370 |
NEXT |
||
|
380 |
HQR2 |
||
|
420 |
Tl - (Nl - Ml» |
/ 2 |
|
|
430 |
T2 - (N2 - M2> |
/ 2 |
|
|
440 |
M - Tl |
/ T2 |
|
|
450 |
IF W < |
1.46333333 THEN 480 |
|
|
460 |
XS - 139iZS - 139 / W |
||
|
470 |
GOTO 490 |
||
|
400 |
XS - 93 |
« MtZS |
- 95 |
|
490 |
FDR Y |
- A2 TO |
B2 STEP H2 |
|
S00 |
FOR X |
- Al TO |
Bl STEP HI |
|
510 |
GOSUB |
690 |
|
|
520 |
NEXT |
||
|
530 |
NEXT |
||
|
540 |
FDR X |
- Al TO |
Bl STEP H3 |
|
550 |
FDR Y |
- A2 TO |
B2 STEP m |
|
560 |
GOSUB |
690 |
|
|
370 |
NEXT |
||
|
580 |
NEXT |
||
|
600 |
END |
||
|
610 |
BDSUB |
790 |
|
|
620 |
XT - X |
- Y » CS |
|
|
630 |
ZT " Z |
- Y « SI |
|
|
640 |
IF XT |
> Nl THEN Nl - XT |
|
|
650 |
IF XT |
< Ml THEN Ml - XT |
|
|
660 |
IF ZT |
> N2 THEN N2 - ZT |
|
|
670 |
IF ZT |
< ri2 THEN M2 - ZT |
|
|
680 |
RETURN |
||
|
690 |
QOeUB |
790 |
|
|
700 |
XT - 140 + INT (XS » (X - |
||
|
+ Tl) |
/ Tl) |
||
|
710 |
ZT - 96 - INT |
(ZS « <Z - V |
|
|
T2) / |
T2> |
||
|
720 |
HPLOT |
XT.ZT |
|
|
780 |
RETURN |
||
|
790 |
z - - |
1 / (X |
« X + Y « Y H |
|
800 |
RETURN |
170 180 190 200 210 215 U 220 Q ■' 230 CS 240 51 250 HI
INPUT "UPPER PHI LIMIT; ";B2 INPUT "SLICES IN THETAi"jN INPUT "SLICES IN PHIs'-jM INPUT "OBSERVATION ANt3LEi";Q PRINT "SCREEN SCALING IN PROGRESS" .0174532925
- Y » CS - Nl
« 51
.5)
Program 8: Spheri-^Apple version
100 HCDLOR- 3
130 HOME
140 INPUT "LOWER THETA LIMITi"jAl
150 INPUT "UPPER THETA LIMITi"|Bl
160 INPUT "LOWER PHI LIMIT* "jA2
Q
t U
COS (Q)
SIN (Q>
<B1 - At)
/ 279s H2 - <B2 - A2) / <N
- 1)
260 H3 - (Bl - Al) / (M - L):H4 - (B2 - A2) /
279 270 Ml - 999999991 M2 - MliNl >= - MliN2
Nl
280 290 300 310 320 330 340 350 360 370 380 420 430 440 450 460 470 480 490 500 N2 + 510 520 530 540 550 560 570 5B0 600 610 620 630 640 650
FOR Y - A2 TO B2 STEP H2
FOR X = Al TO Bl STEP HI
GOSUB 610
NEXT
NEXT
FOR X - Al TD Bl STEP H3
FOR Y - A2 TO B2 STEP H4
GOSUB 610
NEXT
NEXT
HGR2 Tl - (Nl - Ml) / 2 T2 - (N2 - M2) / 2 W = Tl / T2
IF W < 1.46333333 THEN 480 XS = 139! ZS = 139 / W
GOTO 490 XS = 95 » W:ZS = 95
FOR Y = A2 TO B2 STEP H2
FOR X = Al YO Bl STEP HI
GOSUB 690
NEXT
NEXT
FOR X « Al TO Bl STEP H3
FOR Y - A2 TO 52 STEP H4
GOSUB 690
NEXT
NEXT
END
GOSUB 790 XT = XT - YT » CS ZT - ZT - YT * SI
IF XT > Nl THEN Nl - XT
IF XT < Ml THEN Ml ■ XT
70 COMPUTE Moy1984
i'v^/i
k'4«
-■^
"^.5
^
"^^
m^
Q
-4f*''-'
"Uriif
.yji
mi/
i"-+-
<s^*
It was as peaceful a day as New York ever gets, when suddenly ttie sky went dark and a monstrous droning noise filled tfie air. Hordes of grotesque aliens were swooping down from all sides, biting into the Big Apple as if 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 anyone was going to save the city it would have to be me. I leapt into my rocket and began blasting away. I thought I stood a fighting chance, but fuel 's running low... another wave of invaders on the horizon. . . signing off. . .
SAVE NEW YORK: For Oie Commdore 64.
R E A T I V E SOFTWARE
•coummonE sris a tmdekauk of cmnoooRi eucTnonics. ltd
c mjCHlATIVCSOnWAK
660 IF ZT > N2 THEN N2 - ZT
670 IF ZT < M2 THEN M2 - ZT
680 RETURN
690 GOSUe 790
700 XT - 140 + INT (XS « (XT - YT * CS - N
1 + Tl) / Tl> 710 ZT - 96 - INT (ZS * <ZT - YT « SI - N2 ,+ T2) / T2)
715 IF XT < a THEN XT - 0
716 IF XT > 279 THEN XT - 279 720 HPLDT XT,ZT
7B0 RETURN
790 XA - X * UiCl - COS (XA)iSl - SIN (XA >
B00 YA - Y « UiC2 - COS (YA)lS2 - SIN (YA
) 820 XT - (4 + CD « C2 830 YT - (4 + Cl> « S2 840 ZT - SI B50 RETURN ©
Use the card
in the back
otthis magazine
to order your COMPUTEi Books
LEARN
MACHINE LAMIGUAGi
• Write Fast-action Arcade-stvls graphics
• Fulty use the Music svnthesizer
• Completeiv understand the Computer
• Develop your skills inventory
Learn with the Tutor/at tha t comes complete with a Full set of professional quality development tools.
DEVELOP-64 4.0
IS NOW
FAST!!!!
Assembles 2000 lines of coda in under 15 seconds!
• Superfsst • Macros • 2600 Lines of code in memory Expandable by disk or tape file • Assemble direct to disk or tape or memory • Powerful Co-residont Full-screen editor, debugger and decoder • Decoder dis^jssembles programs on disk or tape or in memory • Built-in disk wedge • Program trace, Single step, Execute • Set 10 breakpoints and/or Gopoints • Full-screen memory display and modify
PLUS the Machine Language Programmer's Bible:
"Inside the Commodore 64" -^ /f
9s ^t^^mjfmlk
'69
Plu& $3.1X1 postage and handling. (Minn residents add 6%}
^
P.O. Box 7426 Minneapolis, MN S5407
Call Toll-Free 1-800-328-0145 or in Minnesota call: (612) 871-4505
fe^:
ATTENTION GOIi/IMODORE 64 OWNERS
WE^LLMCK YOU
If yo
Machine?^ i ane coniror or your i
NEW IMPROVED .r. saJ.
WITH UNGUARD*
Package Includes
1) Complete and thorough users manual j- i~y
2) Copy with one or two drives A.
3) Investigate and back-up many "PRO- TECTED" disks '^^
4) Copy all file types including relative -^ types
5) Edit and view track/block in Hex or ASCII s^
6} Display full contents of directory and '^^^ .
7) Change program names, add, delete ^ /■ '-•' files with simple keystrokes '''i' Clone N^*^
8) Easy disk initialization
9) Supports up to four drives
'UNGUARD Now allows you to read, write and verify bad sectors and errors on your disk making it easy to back-up most protected software.
''i' Clone NV''
$4995 =
Dealers & Distributors Inquiries Invited
CALL (201) 838-9027
1342 6 Rt. 23 "■ Butler, N.J. 07405
POWER LINE PROBLEMS?
SP1KE-SPIKER® ...THE SOLUTION
Protects, orgoniies, controls compulers & sensitive electronic equipment. Helps prevent softwore "glitches ', unexploined memory loss, and equipment dotiiage. Filter models ottenuote conducted RF interference. 120V, 15 Amps. Other models ovoiloble. Ask for free literature.
DELUXE POWER CONSOLE
$89.95
filter. B individually i<wilchcd vxkeli, KahJ. rndn switch. & lite.
QUAD-II $59.95
Transient cbtorber DimI 3 s?age filter, 4 sockets. SiTe.
QUAD-I $49.95
Troosiert crtKortw, 4 iock«ts.
MINI-II $44.95
Tron^iefit obiorbw, 3 itege fiher. 2 sockets.
MINI-I $34.95
Transitrt nb^wber, 2 jockets.
b!4GI®
6564 Ruth Rd .OilJl CP B«lhlet«m. Pi 1801 7
DEALER INQUIRIES INVITED
215-837-0700
Out 0* STOte Order loll Ftm
1-800-524-0400
■CODsoddSa.OO -1- Ship,
72 COMPUTE! Mov1984
SEE THE LIGHT!
Quality Software that Outshines the Rest
Programs for the Commodore 64
dMOS"
Database Manasement Operating S^tem
The BEST data base management too! tor ttie cotlectJon, arrangement and display of I alphanumeric data.
A Unicpje pattern matching and searching capatMlities make dMOS™ the easiest DB system available on the marltet. ^.,
Features: fl
• Map search technique to achieve a "logical AND",^ while searching between fields.
• Display records found, or NOT found by a search,
• Rearrange fields, ^i
• Suppress fields and field titles. j^^
i
• Re-encodes program.
• Insert short (10 character) text. •^ Selectively print records.
$39^
The Program Security System \
Set up program security in minutes, ck up your personal, financial or business records. 3 types of protection:
Modifies diskette directory.
Selectable and reassignable 7 digit access code.
Missing Key ,.
^^^i A reset System
^^^^^ Restores your BASIC Program.
^^r^ /^fter programming for hours you
' press RUN for a final check of your work —
' the computer locks up. You press RUN, STOP. . .
' nothing — you press RESTORE. . . nothing — you
, look for the missing key but it isn't there. You
I have to turn off your computer and lose hours of work!!
I Now Add the Missing Key™:
[ • Press the "Missing Key""" and the computer k resets itself from any lockup, and your BASIC \ program is restored.
Load and run the program included.
Takes nothing away from your computer, neither
memory nor a plug-in port.
Attaches to your C64 keyboard or any other
convenient location.
Will not void your CBM warranty. $29^^
and announcing
Boss
TM
\'.
Personal Phone Directory Program
Designed to store and organize your personal phone listings.
TO &ssf'has coiifipletd cohtmr&T Vs category titles and entries
Software by SoftPeople ■ Programs for the Commodore 64 m Connecting People with Great Ideas.
Sof tPeople Inc.
2042 Marshal! Ave. St. Paul, IVIN 55104 (612)644-1551
Dealer Inquiries Invited 1-80(M47-3273
Special P.O.P Packages & Prices Available
PICTURE PERFECT
For Atari And Commodore 64
CoyV Ison
Construct screen art on the Atari witli a joystick (Did basic shapes fortned by redefining characters. You also can save a picture to disk or tape for later luezvini^. The Commodore 64 version, called "Hi-Res Graphics Editor," emploi/s sprites to transport and transform even the most intricate designs.
"Picture Perfect" is not a game that pits you against the computer, but instead is a way to create pictures, patterns, and designs by using the com- puter and your imagination.
Type in the listing and SAVE a copy, making sure that line 1520 is exactly as shown. When you run the program, you will be prompted for the filename to be used later when saving or loading your picture file. Tape users should enter C: for the filename. Disk users can enter anv legal filename, but it must be prefixed with D:. Once vou have selected a valid filename, a picture of a castle will be displayed. Press START, and two rows of nine shapes will appear at the bottom of the screen, below the drawing area.
Touch the OPTION key to see two new rows of shapes, and touch OPTION again to toggle back to the first two rows of shapes. These are re- defined characters, to be used in your drawings.
Choose A Shape
A question mark will blink on top of the shape to indicate your position. Using a joystick plugged into port 1, you can move across the two rows of redesigned shapes. To pick up one of the shapes, stop on top of it and touch the joystick button. The question mark will then move to the upper right corner of the drawing screen.
74 COMPUTE! May 1984
You can now place the redesigned shape anywhere on the screen by touching the joystick button. When you want another redesigned shape, touch the SELECT key. This places your cursor on the two rows of shapes so you can pick up another design.
To erase a shape, move the question mark on top of it and touch the space bar. Should you want to erase a large portion of a picture, touch the E key. A red E will replace the question mark on the screen. By holding down on the joystick button and moving the red E, you will be able to quickly erase a large portion of the screen. To stop erasing, simply press the E key again. If you want to erase the whole screen, touch the CLEAR key.
Storing A Picture
To store a picture on tape, first place a tape in the recorder or your disk in the drive and press PLAY and RECORD, then touch the S key on the key- board. The program will save the picture on tape for you. When using tape, be sure that you press PLAY and RECORD before you touch the S key. No RETURN is necessary and the saving will start immediately.
To save a picture to disk, first insert the disk in the drive and close the door. Then touch the S key.
Loading Your Picture
If you have a picture already stored on a tape or disk and want to load it into the program, you need to have Picture Perfect in the computer. Place your tape into the recorder (or the disk into the disk drive), press PLAY (for cassette) then touch the L key. When the picture is loaded, it
Last Night, CompuServe turned This
Computer into A Travel agent for Jennie,
A Stock Analyst For Ralph, And now,
IT'S Sending Herbie To Another Galaxy.
NO MATTER WHICH COMPUTER
YOU OWN, WE'LL HELP YOU GET
THE MOST OUT OF IT.
If you've got places to go, CompuServe can save you time and money getting there. Just access the Official Airline Guide Electronic Edition— for current flight schedules and fares. Make reservations through our on-line travel service. Even charter a yacht through "Worldwide Exchange."
If your money's in the market, CompuServe offers a wealth of
prestigious financial data bases. Access Value Line, or Standard and Poor's. Get the latest information on 40,000 stocks, bonds or commodities. Then, consult experts like IDS or Heinold Commodities. Ail on line with CompuSeA'e.
Or if, like Herbie, intergalactic gamesmanship is your thing, enjoy the best in fantasy, adventure, and space games. Like MegaWars, the ultimate computer conflict.
To get all this and more, you'll
need a computet; a modem and CompuServe. CompuServe connects with almost any personal computer, terminal, or communicating word processor To receive an illustrated guide to CompuServe and learn how you can subscribe, contact or call:
CompuServe
Consumer Information Service. P. O. Box 20212 5000 Arlington Centre Blvd., Columbus, OH 43220
800.^48-8199
In Ohio call 614-457-0802.
An H&R Block Company
DY= (S=13) - (S=l 4 >
IF D X < ";■ 0 OR D Y ■-: > 0 THEN G D S U B
0
will be displayed. Once again, be sure that vour f- ^£C' DX= (S = 7) -(3=11) tape is readv and that vou have the PLAY button pressed before you touch the L key.
If you don't want to type in the program, I el 44ei dv = dv + dx: Da = DO-t-Dr
will make copies (for the Atari only) on cassette, if le 450 if o\f< 1 then ov= 1 a you send the usual $3, a cassette, and a stamped, self-addressed mailer to:
Coy hoii 605 Fifth Ave. Coimm/, AR 72032
|
PG |
4 1 0 |
|
,- T |
4 261 |
|
6? |
4 30 |
|
EL |
4 4^1 |
|
LE |
450 |
|
LH |
4 60 |
|
JC |
4 70 |
|
35 |
4 80 |
|
DE |
4 90 |
|
PO |
5 00 |
|
GE |
505 |
|
EA |
510 |
|
Ch |
5 20 |
|
: c |
525 |
Program 1: Atari Picture Perfect
IF Q V ; 1 8 THEN O V = 1 IF DD<; 1 THEN D0=19 IF DDM9 THEN DD=1 LOCATE QV, DO. Q POSITION DV.DO:'"' #6;'"^" POSITION POV.PDD-. ? #6;" " FOR T=l TO 10: HEX! T POSITION DV.DO:? «6;CHR«<L-> POSITION POV.PDD:? #6;CHR«(ft) -30 IF STRIG(0)=0 THEN POSITION OV . DO : "^ #6; CHR* (A) JJ 540 IF PEEK (53279) =3 THEN