Portable Operating SystemInterface for Unix (POSIX) is a vendor-independent interface between an operating system and an application program specified by the Federal Information Processing Standard (FIPS).
This POSIX interface definition supports the portability of Unix-based programs. According to ISO/IEC 9945-1, the standard defines a standard operating system interface, including an interpreter and common utility programs to support application portability at the source code level.
According to this specification, programs written to conform to Posix can be ported to other operating systems. Posix was adopted by IEEE in 1988, it uses Unix system services and can be implemented on other operating systems.