My first PC was a Honeywell XT clone running Xenix. It had a black and white display, an acoustic-coupled modem (I don't remember how fast, probably 300bps though), and an attached serial terminal. There was a lineprinter, too.
I hated that thing. Dad taught me to type papers for school using vi (and if he was running vi on his terminal too, the machine slowed to a frickin' crawl) and eventually broke down and got me a copy of DOS (2.1) so I could play games. But mostly it ran Xenix, which was uttlerly incomprehensible. DOS had a nice tutorial, so it was easy to learn. Xenix? Well, I got a sheet of paper with the names, but not descriptions, of all the commands.
People who complain about Linux nowadays, try THAT.
Couple years ago I converted a machine that had been running some latter-day version of Xenix to a Linux box. Kind of a neat project. The thing had been running a custom application that wrote data out to plaintext files in comma-seperated form, so it was dirt-simple to make a perl script to do the same thing. It was really weird, though, going between a modern *nix like Linux, and crufty, ancient Xenix. Even modern SCO unix releases haven't outgrown it. I don't think OpenServer comes with ksh, for example.
Ever use Coherent, iGary? That's another one of those ancient history lessons. Or Dell Unix? Or AIX/x86?
Considering how many PC Unix systems there were, you'd think one of them would've caught on.