I've been collecting old UNIX systems for a while now; mostly AT&T UNIX systems. At various times, I've had Fifth, Sixth, and Seventh Edition UNIX running, then System III, System V Release 2, 3, and 4.

At present, I'm only running three: Seventh Edition, System III, and System V Release 4. These are a good compromise for both examining the evolution of UNIX and for having useful systems at hand.

For anyone interested in the technical history of UNIX, actually looking at the various systems is an incredible experience, made even more interesting by reading the excellent documentation that came with each one, or available on the net.

Each successive version adds a measure of sophistication and polish to the kernel, API, userland functionality, and documentation. Yet each is clearly UNIX, and anyone reasonably familiar with any UNIX variant would probably be able to get around in any of them with a little work.

I will be continuing my exploration in the coming weeks and will write a follow-up to this post.