I'm reading in, Kernighan
& Plauger's 1981 edition of Software Tools in Pascal and in
the book, the author's mention Bill Joy's Pascal and Andy
Tanenbaum's as being rock solid. So, a few related questions:
1. What edition of UNIX were they likely to be using?
I'm afraid I can't speak to your 2nd and 3rd questions, but I can offer what I think is a reasonable guess about the first.
One of the neat things about Unix and Unix-adjacent books of that era is that very often the copyright page held some information about the production of the book itself. I just so happened to have a copy of, "Software Tools in Pascal" sitting on my desk, and it says, "This books as set in Times Roman and Courier by the authors, using a Mergenthaler Linotron 202 phototypesetter driven by a PDP-11/70 running the Unix operating system."
Given the PDP-11 and the date (1981) one may reasonably conclude that it was running 7th Edition. I imagine the pascal was Joy's, from Berkeley.
- Dan C.