Excerpt from the Wikipedia page
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.
- Silicon Graphics - Irix
- IBM - AIX
- Sun Microsystems - Solaris
- Hewlett Packard - HP-UX
Unix is officially trademarked as UNIX.