Comment by pjmlp

> Unix wasn't the first operating system to be written in a high-level language. The Burroughs OS was written in Algol, Multics was written in PL/I, and much of VMS was written in BLISS. None of those languages became popular.

Of course, they weren't available as free beer with source tapes.

> Apple replaced the original Macintosh OS with a system based on a Unix.

Only because they decided to buy NeXT instead of Be.

Had they bough Be, that would not been true at all.