Unlike the Apple ][, the Apple 1 never had BASIC in ROM. The Apple 1 booted into a monitor program, which enabled the user to type in machine code for a program (as Steve Wozniak often did), or load a program using the optional cassette interface (how most users loaded BASIC). The monitor also provided routines for reading the keyboard and printing characters to the screen.
Woz wrote and assembled the monitor program by hand -- without the assistance of another computer -- as he had also done for the Apple 1 BASIC. However, this raising a software development bootstrapping problem: How was he able to get the machine code actually into ROMs for the Apple 1 in the first place?
- Borrow/use someone else's (E)PROM writer (e.g. at work, or from the Homebrew Computer Club)?
- Build his own (E)PROM writer (e.g. from discrete logic)?
- Pay a company to do it (expensive, unlikely)?