By Kenneth Bernholm
Unix is my preferred class of operating system for general purpose computing because of the Unix philosophy and the elegance of the original design. The inaugural Unix saw life in 1969 but I didn't get my first exposure until 1985 at Køge Business College. They had a DDE Supermax running a variant of Unix System III called SMOS. The year after at what was to become Copenhagen Business College I was (to the best of my recollection) introduced to Siemens Nixdorf SINIX which was based on Unix System V, and at Commodore in 1990 I got to mess around with Amiga Unix which was also built on Unix System V. It wasn't until the early nineties that the first free Unix variants became available under Open Source licenses and I could run Unix at work and at home.
Around the turn of the century I managed to get hold of a couple of proprietary Unix workstations: A Sun Sparstation 20 purchased on a visit to Silicon Valley and a SiliconGraphics Indy as part of a trade. The Sparcstation ran SunOS (based on BSD) and Solaris (based on Unix System V). The Indy ran IRIX which was also based on System V but with some BSD extensions. I learned a lot from digging into these systems, but ultimately I sold them off. The hardware showed its age and could not keep up with newer versions of the operating systems. At some point I also owned an Apollo/Domain workstation (possibly a DN3500, I really don't remember) running Domain/OS which was a beast of its own that implemented parts of System V and BSD for Unix compatibility. The hardware could also run both System V and BSD directly but I never had these tapes.
As far as BSD systems go, I prefer the FreeBSD variant for several weighty reasons:
Dennis MacAlistair Ritchie, creator of the C programming language and co-creator of Unix, is reliably quoted for saying, that most of them at Bell Labs were running FreeBSD. Endorsements doesn't come much better than that.