sunos

from The Free On-line Dictionary of Computing (8 July 2008)

SunOS

   <operating system> {Sun Microsystems}' version of {Unix} for
   Sun {workstations}.  SunOS is similar to {BSD Unix} with some
   {SVR4} features and {OpenWindows} 3.0.

   After version 4, SunOS was integrated into Sun's {Solaris}
   "operating environment".

   (1999-03-26)