[blippage]

I could be wrong, but I think Unix was originally written in assembler, which isn't portable.

Unix first appeared on a PDP-7 (not PDP-11). PDP-7 was pretty old even by the standards of the time.

"Originally, UNIX was written in PDP-7 assembly, and then in PDP-11 assembly, but then when UNIX V4 began to be re-written in C in 1973 and was run mostly on the PDP-11.

So far as I can tell, there is no Ancient C compiler that targets the PDP-7, nor any provision for running UNIX V4 or later on the PDP-7" [0] The link also contains some other interesting commentary.

I seem to recall that Thompson wanted to write code in Fortran.

I'm probably getting a few details wrong. The systems were extraordinarily constrained, something like 4K of RAM. "++" exists because it was more concise that "+= 1" (although K&R C uses "=+ 1", I think). They really wanted to make every byte count.

[0] https://retrocomputing.stackexchange.com/questions/6194/why-...

[7speter]

Thanks for painting a mire elaborate picture of how it all went. Of course c had to be compiled on some system, and there were probably a good variety of systems around back then.