Apple - What operating system was installed on the original Apple 1?

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

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.

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.