Myself it was v6 (most likely the typesetter version). What I’d like to see discussed is how people today learn to write, enhance, design, and otherwise get involved with an OS. When I was teaching at UCSD my class on Unix Internals used writing a device driver as the class project and covered an overview of the Unix OS using the Bach book. Even then (the late 80’s) it was hard to do a deep dive into the whole of the Unix system. Today Linux is far too complex for someone to be able to sit down and make useful contributions to in a few weeks possibly even months, unlike v6, v7 or even 32v. By the time of BSD 4.1[a,b,c] and 4.2 those had progressed to the point that someone just picking up the OS source and trying to understand the whole thing (VM, scheduling, buffer cache, etc) would take weeks to months. So what is happening today in the academic world to teach new people about OS internals? David