Levy_S-Hackers-Heroes-Computer-Revolution

its competitor to the Apple. On first sight, it appeared to be some sort of jazzed-upgame machine with a keyboard. In fact, it had a slot to put cartridges inside, amark that the machine was geared at least in part for novices too befuddled tohandle even a tape cassette, let alone a floppy disk. There wasn't even a decentmanual. John Harris played with an 800 in the store, and discovered that, like thePET and unlike the Apple, it had full-screen editing. But he wanted to know whatwas inside it, so he went to another store, where a salesman slipped him a piece ofpaper with some commands for this new computer. Like some secret code for useby the French Resistance. No code-breaker devoured a message as avidly as JohnHarris did these papers. He discovered that the Atari had a set of keystroke graphicsymbols, a high-resolution mode, and a separate chip for sound effects. In short,exciting new features, every feature Harris liked on the PET, and even the thingshe grudgingly considered worthwhile on the Apple. He bought an 800.He began programming in BASIC, but very soon realized that he would have tolearn assembly language to do the games he wanted to do. He quit working at thebank and got a job at a company called Gamma Scientific, which had needed aprogrammer to do assembly-language work on its system, and was willing to trainsomeone.Transferring his new assembly-language skills to the Atari was difficult. The Atariwas a "closed" machine. This meant that Atari sequestered the informationconcerning the specific results you got by using microprocessor assemblylanguagecommands. It was as if Atari did not want you to be able to write on it. Itwas the antithesis to the Hacker Ethic. John would write Atari's people and evencall them on the telephone with questions; the voices on the phone would be cold,bearing no help. John figured Atari was acting that way to suppress anycompetition to its own software division. This was not a good reason at all to closeyour machine. (Say what you would about Apple, the machine was "open," itssecrets available to all and sundry.) So John was left to ponder the Atari'smysteries, wondering why Atari technicians told him that the 800 gave you onlyfour colors in the graphics mode, while on the software they released for it, gameslike "Basketball" and "Super Breakout," there were clearly more than eight colors.He became determined to discover its secrets, the mysteries of its system, thebetter to extend it and control it.For the quest, John enlisted a friend who knew assembly language. They got holdof a cassette-tape disassembler written in BASIC, something which broke downprograms into their object code, and disassembled the software sold by Atari lineby line. Then they would take these weird instructions, which accessed all sorts ofoddball memory locations on the 6502 chip inside the Atari, and poke them intothe machine to see what happened. They discovered things like "display listinterrupts," which enabled you to use a greater number of colors on the display