Are you working through the 1st or 2nd edition of the book ? I think these are the ones that used ACK.

I’m working through the third edition which I believe is also ACK based as far as I can tell. MINIX version 3.1.0?

I remember after I read the 1st edition, bought MINIX ($150 !!), and then was very annoyed to find that the compiler source was not included. Luckily it was '89 or '90 and GCC sources were available.