AT&T System V Unix (1991) 17 Unix

AT&T UNIX System V ("System Five"), first released in 1983, is significant as it was one of the first commercial versions of the Unix operating system. It was the result of much collaboration between vendors and became the core basis for many other operating systems including Xenix, AIX, UnixWare, Solaris, and HP-UX.

• 2.x

Intel Unix System V (1990) 2 Unix

Intel Unix System V was a rather uncommon Unix variant developed and distributed by Intel, for IBM PC compatible hardware. It was considered "plain vanilla" compared to other distributions, adding little beyond AT&T's codebase.

• 2.x

Xenix Software Development System (1983) 0 Unix

The Xenix Development System is a set of compiler and code tools for the Xenix operating system.

• 1.x (TRS)
• 1.00 (IBM)
• 2.00 (IBM)
• 2.x (SCO)