known as Digital UNIX (originally DEC OSF/1 AXP). As its original name suggests, Tru64 UNIX is based on the OSF/1 operating system. DEC's previous UNIX
Specification, although system developers generally aim for compliance with POSIX standards, which form the core of the Single UNIX Specification. The latest
by Apple. Darwin is mostly POSIX-compatible, but has never, by itself, been certified as compatible with any version of POSIX. Starting with Leopard, macOS