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I am trying to research how software enabled users to interact with the hardware on the original Apple.

What operating system was installed on the original Apple 1?

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3 Answers 3

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I used to own an Apple ][. It had floating-point BASIC installed in the upper 16kb of memory. "Booting" took maybe 1 second - flip the switch -> Beep -> it's ready.

If you bought a disk drive, the boot loader was in a 256 byte (bytes, singles, no M or k) ROM on the interface card. Apple DOS was written onto every floppy disk and took up about 10kb of RAM.

Some trivia for your project:

  • The Apple ]['s documentation included a fold-out circuit diagram of the computer's electronics. Just in case you needed to repair it.

  • The documentation also included the complete source code (6502 Assembler) of the operating system. Maybe 30 pages. Assembler at the time was a 1:1 representation of the machine code.

  • I wrote Apple (on paper - no internet back then) asking for the Integer BASIC source code for comparison. They wrote back and said they would be happy to send it, but they don't have a copy. Wozniak apparently wrote Integer BASIC himself, compiled it with a pencil and the Motorola 6502 data sheet, and typed in the resulting hexadecimal opcodes by hand. All bow to the Greatness of The Woz.

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  • This is incredible and what a genious The Woz is! I am amazed. Thanks a lot for sharing.
    – Lee
    Commented Mar 26, 2015 at 2:46
  • why does this answer exclusively talk about the apple ][ (aka apple 2) when the question explicitly asks about the apple I (aka apple 1)? Commented Jul 25, 2022 at 14:52
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The original Apple 1 came with a 256 byte ROM containing Steve Wozniak's monitor program. This program allowed the user to inspect memory, write to memory and run programs. There was also a very basic line editor that permitted the use of backspace and escape keys.

The Woz Monitor

Apple 1 emulator in Javascript

If you want to try out the emulator, be aware that the Apple 1 does not have a power-on reset and requires the user to hit the ESC key to initialize the monitor.

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According to Mactracker, it was "Apple Integer BASIC with optional Cassette Interface".

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  • Great resource you pointed out there. I immediately downloaded Mactracker. Much appreciated.
    – Lee
    Commented Mar 26, 2015 at 11:09

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