HP-UX

HP-UX is Hewlett-Packard's version of the UNIX operating system, it was originally released in 1984 for Motorola based workstations and servers and was then based on UNIX System III, it was later ported to HP's PA RISC processor architecture and Intel Itanium with the current codebase being forked from UNIX System V.

HP-UX is one of the few UNIX like systems that comply with the Single Unix Specification alongside Solaris and AIX