How Steve Wozniak Wrote BASIC for the Original Apple From Scratch

To lionize the50th day of remembrance of BASIC , Steve Wozniak has written some memories about his first experiences with this popular language — and how he created his own BASIC from scratching for the Apple I and Apple II computers . An incredible exploit . Enjoy!—JD

In 1967 or 1968 , as a senior in high schoolhouse , our electronics instructor ( the best instructor of my life in many teaching regards ) set for me to go to a ship’s company in Sunnyvale ( Sylvania ) to program a computer because I already knew all the electronics in course of study at schoolhouse . Mr. McCollum did this for students with electronics ability every year , finding local companies with engineers and projects that would permit high school students come and and get some experience . I learned and program in FORTRAN on this IBM computer .

I first experienced BASIC in eminent school that same year . We did n’t have a computer in the school but GE , I think , brought in a terminal with modem to advertize their time - sharing line . A very few of we bright math bookman were give some pages of education and we wrote some very simple computer program in BASIC . I saw that this was a very mere and easy - to check language to start with , but that terminal was only in our shoal for a few days . I was asked by our pass maths teacher to write a page on why I thought this would be a good affair for our school to have . I did indeed write a page about lucid thinking and job solving but our school did n’t go ahead and get into the time - portion program .

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In my college years my higher level programming languages were of the scientific mold , FORTRAN , PL-1 , Algol . Of course I program a lot in many assembly languages too , in college and on my own .

In the Homebrew computer club we had a mates of books go around that I like to call ‘ bibles ’ . One was Computer Lib / Dream Machine by Ted Nelson , key a next cosmos of hyperlinks to further the meaning of thing in written material . His ideas were like scientific discipline fiction but we all knew that they were achievable , technically , and we were all apostles for this agency of look at the hereafter of computation . The other ‘ bible ’ was a book “ 101 Games in BASIC . ” I was a sports fan of computing gadget games and knew that as soon as I had a computer of my own I would want to typewrite in all these games to play . pronounce by my own feelings , I bear that this would be a key to commence a place calculator revolution . The non - businessman in me prevents me from talking about market place or finance .

I did not know for indisputable what a real computing machine need to do the vainglorious financial jobs that computers did for companies , the computers that sell for Brobdingnagian amounts of money . Those were worthwhile computers . All I knew was that which was close at script . I ran simulation of chip designs and logic designs at HP , working on reckoner . My computer would have to do that . My figurer would also have to play games . At least then I was certain that my computer could possible do the important things that high price figurer do , but I was n’t certain .

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The key to games was BASIC . Bill Gates was unknown except in the electronics hobby world . Everyone in our guild knew that he ’d pen BASIC for the Intel microprocessor . I sniffed the wind and cognize that the key to crap my calculator good ( democratic ) was to include a high - spirit level language and that it had to be BASIC . Engineers programming in FORTRAN were not go to be what would start a habitation computer gyration .

Learning the language and writing a BASIC interpreter

The trouble was that I had no knowledge of BASIC , just a spare memory that it had line numbers from that 3 - mean solar day eminent - school experience . So I picked up a BASIC manual of arms recent one night at HP and started reading it and reach notes about the control of this language . Mind that I had never take a course in compiler ( or interpreter ) write in my life . But my friend Allen Baum had sent me xerox copies of page of his texts at MIT about the subject so I could take that I had an MIT Department of Education in it , ha ha . In my 2d year of college I had sat in a math analysis division trying to teach myself how to start write a FORTRAN compiler , know nothing about the science of compiling program writing . I went back to this memory and originate writing code for my 6502 microprocessor to understand in lines that a user typed for psychoanalysis and error checking .

I knew about syntax charts and created one for this BASIC . I did not know that HP BASIC was extremely unlike than DEC BASIC , the one that the book “ 101 Games in BASIC ” used and that Bill Gates had publish . I figured all BASIC ’s were the same but HP ’s differed greatly when it came to chain of alphabetic character . I finished my phrase structure diagrams and they were complete . But I had in the back of my head that I could be a star , that I could get a picayune renown in the hobby world , like Bill Gates , if I created the first BASIC for the 6502 . To spare a bit of time , I dismantle the float point operations out of my syntax diagram . I needed to save integer base simulations for my HP workplace and games are establish on logic , which is integer . I cast off float point routine ( unity with decimal point ) only to save a few calendar week and have a better chance of being the first to develop this BASIC on the 6502 . You might see back and see that I included be adrift point arithmetical routines in the ROM of the Apple ] [ but I never cash in one’s chips back to work them into the BASIC . When you code by bridge player ( could n’t afford a time - portion account ) it ’s hard to make changes in the middle structure of thing that have to be at fixed reference .

Breakout on Integer Basicrunning on the original Apple II .

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I did n’t bonk about compiling program write other than perchance . But I did know about flock and things like converting expressions into RPN using mass . Our HP calculators used RPN , in fact . Thinking about how to write this language I came up with my own proficiency , not like anything out of a Word of God . I wound up with what I cry NOUN and VERB stacks ( operands and operator ) . I put shred in my syntax diagram but every operator in it had a number accord to it ’s linear position in this 256 - byte or 512 - byte ( I forget ) tabular array . The 41st operand had the code of wheeler dealer # 41 .

I also had a listing for every operator of 2 priorities . One was its tendency to go forward of other operators . For case , the + wheeler dealer would get a * operator to go on first . But I needed a second table of the resistance to being push into action to deal things like parentheses . I had no mind if I was on a correct racetrack but it worked right and did what I needed . It did n’t have to follow from a book .

I enjoyed demonstrate this BASIC at the Homebrew Computer Club . I never saw my name in print so I did n’t get that ‘ Bill Gates ’ fame , but I was known in my club . This was even before Steve Jobs saw that my computer live . As time get by I only had to write one subprogram after another for each of those numbered operators . Every nightclub meeting I ’d have a few more commands that worked amply .

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With the Apple ] [ I had the TV and calculator memory board one and the same so that the microprocessor , modify maybe a million ( overdone ) turn a instant , would modify a million screen byte a second . Atari arcade games were computer hardware then but now the game could be implemented as software , using 6502 machine language programming . BASIC is an interpreted speech . BASIC goes over the private letters of each command as it execute , check what to do . It is maybe 100 or 1000 times slower than machine language as a result . But one day I was curious as to whether you could program moving objects just in BASIC and see them move like naturalistic animation .

I had designed Breakout for Atari in computer hardware . I wondered if I could programme this simple animated arcade biz in BASIC ? I hump I could program it in simple machine spoken language . Since it was my own BASIC I move to the sentence structure chart and add up commands to plot color and to draw horizontal and upright personal credit line . I then searched buffalo chip manual and chose a microchip with 4 timers ( 555 vogue timers ) on one chip . I used that with some package to read paddle positions off potentiometers , dials that exchange resistivity according to where you turned the telephone dial . Once I had these mechanisms installed ( burning new EPROMS for the BASIC additions ) I sat down and wrote some simple FOR loops to plot bricks in unlike people of color . I must have tried 30 color combinations in just second . Then I added paddles and score and a testicle . I could adjust program parameters to alter the ball amphetamine and angles . By the way , I guess this is when I added a talker with 1 - bit audio just because you require sounds when a testis pip a brick , etc .

I scream Steve Jobs over to my apartment to see what I ’d done . I shew to him how easy and instantly your could deepen thing like the color of the bricks . Most importantly , in one - half hour I had examine more variations of this game than I could have done in computer hardware over 10 years . Steve and I both realize how authoritative it was going to be now that animated ( colonnade style ) game could be package . More than that , being in BASIC think that anyone of any age could program it .

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I kept about 50 chronological leaflet of papers throughout all my BASIC design work . Each one was labelled GAME BASIC . So you could see where my pass was coming from .

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Another tone : In mellow school or my first year of college I evidence my dad that someday I ’d own a 4 K Data General NOVA . He said it be as much as a down requital on an expensive house . I was KO’d and order him I ’d exist in an apartment .

Why 4 K ?

Because that was the lower limit call for to carry a higher level language . To me a computer had to have more than switch an lights . It had to be capable to feed programs .

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I ’d built a replacement and ignitor computer of my own invention 5 long time before the Apple I. Back then there was no way to afford 4 KB of RAM so it had 256 bytes only .

In the Homebrew days , the summer of 1975 , 3 company enter 4 K DRAM ’s . This was the first clip that 4 KB was unfeignedly affordable . I had to have that much so as to have BASIC be a part of this computer . No pick about it . Hence the minimal RAM on an Apple I or Apple ] [ was 4 KB . Had I not worry about BASIC , I belike would have just built another switch and lights computer with minimum electrostatic remembering and been done with it .

HistorySteve Wozniak

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