What are the really unusual or weird computers?

[Al Kossow]

 > What I want to know is, what did they write the original mac os on.

Lisa

 > And is that what they wrote the subsequent versions on?

Lisa for the System until roughly the start of MPW when there was a
Mac-hosted build environment. The ROM was entirely assembler and could
be built on a Mac Plus with HD20 (slowly).

Parts of the system converted from Pascal to
C through the 80's.