- Original written by Thompson and Ritchie at AT&T to
play video games
- Multics vs UNICS -- UNiplexed Information and Computing Service
- First edition of UNIX released November 3, 1971; included
commands that are still around; a compiler called "b"
- Thompson left for Berkley, BSD released in 1977
- IRIX, SCO XENIX, Ultrix, HP-UX, Solaris, AIX
- IEEE POSIX standard introduced in 1988
- Linus Torvalds creates "hobby" system Linux in 1991