SunOS was the version of Unix used by Sun Microsystems for their workstations that debuted in 1982. After the release of SunOS 4 Sun changed over from using BSD code to using licensed System V code and named the operating system Solaris Operating Environment. SunOS was then retronym Solaris 1.x.
SunOS is still used as the term to describe the core of Solaris. The version number of the SunOS core lying underneath Solaris is 5.{ the Solaris version number }. For example, the latest Solaris release, Solaris 10, runs on SunOS 5.10. Solaris man pages are labeled with SunOS, and the startup sequence displays it, but the term SunOS is no longer used in Sun marketing documents.
