The Computers: Software: Operating Systems: (POSIX Operating Systems )

All operating systems (OSs) in this section support POSIX standards fully or partly. POSIX is an acronym for: Portable Operating System Interface for UniX. Much like TRON, POSIX is not a body of computer code that is compiled and run on some processor. Rather, it is a set of standards (IEEE 1003.1): interfaces, design guidelines, software design specifications, defining (for creating) the computer code that will become language interfaces between an OS kernel and its programs, to give compatibility when moving programs between compatible systems. POSIX is made mostly of features from BSD Unix and Unix System V. Much like Open Source software, all POSIX standards are copyrighted (by the Institute of Electrical and Electronics Engineers, Inc. POSIX Operating Systems Software Computers.

The Portable Operating System Interface ( POSIX ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. (wikipedia)