Excerpt from the Wikipedia page:
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs. Today, it is a modern OS with many commercial flavors and licensees. It has also greatly influenced the development of a free alternative: GNU/Linux.
Unix was originally written in assembly but has since been rewritten in C. It has been branched many times both commercially and open source. One popular variant is the BSD variant which originated from the University of California, Berkeley. It also gave rise to Linux.
- Irix (Silicon Graphics)
- AIX (IBM)
- Solaris (Sun Microsystems)
- HP-UX (Hewlett Packard)
- bsd (UC Berkeley)
Unix is officially trademarked as UNIX.