strangest systems I've sent email from

Chris Hanson cmhanson at
Thu Apr 28 22:51:27 CDT 2016

On Apr 25, 2016, at 7:38 AM, Liam Proven <lproven at> wrote:
> And you do know what Apple MacOS was originally written in, don't you?

The original Macintosh System Software was almost entirely M68000 assembly language.

There were a couple parts of the original System Software that were written in Pascal, but by and large the space constraints of the 64KB ROMs and the 400KB floppy and the desire to eke every last cycle of performance out of the 8MHz CPU led to pervasive use of assembly.

The APIs were defined in terms of both Pascal and assembly, which is what leads people to think that it was written in Pascal.

Of course as time went on, there were pieces added and rewritten that were in Pascal, C, C++, etc. But if you worked on the classic Mac OS chances were you’d need to work in 68K assembly at some point.

Fortunately the 68K had a great instruction set so its assembly wound up being effectively a high-level language. While I generally preferred to install Jasik’s “The Debugger” to do source-level debugging at any level, a huge number of people just used MacsBug for everything, because looking at a disassembly was pretty much equivalent to looking at sources.

  -- Chris

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