I mentioned recently that I have a blind spot about System III and some cultural biases about System V. Well, calling them 'cultural biases' understates things, because it makes the differences between BSD and System V back then sound like the differences between Linux and the *BSDs today. Unfortunately, the split was nowhere near that nice. In fact, I'm going to be blunt: for most of its life, System V was a fairly backwards system.

Do you like job control in your shell? System V didn't have that. Do you like being in multiple groups at once? Nope. Things like symlinks and renaming directories? Of course not. Paged virtual memory? Believe it or not, System V spent a surprising amount of time without it (although less than I thought until I looked it up). The result was that merely using a System V system at the shell level was fairly different from using a BSD system, in a way that is not the case for Linux versus the *BSDs.

(We won't even talk about TCP/IP, which only showed up in SVR4 in AT&T's releases. And I believe that System V was stuck with 14 character filenames for most of its life.)

While System V had a certain amount of good things, it was a very foreign environment for BSD people to use. Many of us didn't like it very much. Some of the strangest and most foreign feeling Unixes I've ever used have been strongly based on System V (pre R4).

With that said, in practice many vendors started from System V but then folded in any number of BSD features; this was especially popular with people who wanted to sell machines to universities. I understand that the result could be a reasonably decent approximation of BSD.

(I'm sure that people who grew up on System V could write up a similar list of important things that BSD was missing. But I do really believe that System V was behind BSD at a technical level for much of its life, even if it had some good bits. Well. Behind what vendors like Sun and DEC were doing with BSD, at least, as actual BSD Unix basically stopped around the time of 4.3 BSD.)