I <3 the BSDs, and they're the reason that the quote from "A Research Unix Reader" stuck in my memory! I started on the linuxes, pre-systemd by many years, and remember system v init levels seeming straightforwards but weird. When I switched to FreeBSD and saw /etc/rc.local, it made far more sense to me. I never even _thought_ about what 'rc' might mean, though.

Seeing the quote from Doug McIlroy many years later lodged in my brain as answering a question I didn't even have, and I've been looking for a good reason to use it ever since.

There's a lot of cool small details like that in so many early white papers about Unix; I'm looking forwards to working through a good number of them over the next 12 months. I think next I'll look at Dennis Ritchie's paper on the impact of migrating Unix from assembly to C. It may give me good opportunity to cover the B->C change as background, which is fascinating to see.