The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines the application programming interface (API), along with command line shells and utility interfaces, for software compatibility with variants of Unix and other operating systems. 

Originally, the name "POSIX" referred to IEEE Std 1003.1-1988, released in 1988. The family of POSIX standards is formally designated as IEEE 1003 and the international standard name is ISO/IEC 9945. 

The standards emerged from a project that began circa 1985. Richard Stallman suggested the name "POSIX" to the IEEE instead of former "IEEE-IX". The committee found it more easily pronounceable and memorable, and thus adopted it. 

Unix was selected as the basis for a standard system interface partly because it was "manufacturer-neutral." However, several major versions of Unix existed—so there was a need to develop a common denominator system. The POSIX specifications for Unix-like operating systems originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents (POSIX.1, POSIX.2, etc.). The standardized user command line and scripting interface were based on the UNIX System V shell. Many user-level programs, services, and utilities (including awk, echo, ed) were also standardized, along with required program-level services (including basic I/O: file, terminal, and network). POSIX also defines a standard threading library API which is supported by most modern operating systems. In 2008, most parts of POSIX were combined into a single standard "(IEEE Std 1003.1-2008", also known as "POSIX.1-2008)."
what does POSIX stand for?
what does it define?
what is POSIX?
by who?
what is the purpose of the standards?
when did the standards emerge?
from what?
who came up with the name?
what had it previously been called?
why did they decide to go with a new name?
which OS was chosen to be the foundation for the standard interface?
why?
how many versions existed?
in 2008, what were the parts combined to?
what was it named?
what else was it called?
how many documents did the original system contain?
what was that increase to?
what were the systems named?
Portable Operating System Interface
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society
The  API, command line shells and utility interfaces, for software compatibility
 POSIX defines the application programming interface (API), along with command line shells and utility interfaces, for software compatibility with variants of Unix and other operating systems. 

A family of standards
The Portable Operating System Interface (POSIX) is a family of standards 
The IEEE Computer Society
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society
To maintain compatibility between operating systems
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems.
Circa 1985.
The standards emerged from a project that began circa 1985. 
A project that began then
The standards emerged from a project that began circa 1985.
Richard Stallman
Richard Stallman suggested the name "POSIX" to the IEEE instead of former "IEEE-IX".
IEEE-IX
 Richard Stallman suggested the name "POSIX" to the IEEE instead of former "IEEE-IX".
It was pronounceable and memorable
 The committee found it more easily pronounceable and memorable, and thus adopted it. 

Unix
Unix was selected as the basis for a standard system interface
It was "manufacturer-neutral."
Unix was selected as the basis for a standard system interface partly because it was "manufacturer-neutral."
Several major ones
However, several major versions of Unix existed—so there was a need to develop a common denominator system
A single standard
 In 2008, most parts of POSIX were combined into a single standard
IEEE Std 1003.1-2008
 In 2008, most parts of POSIX were combined into a single standard "(IEEE Std 1003.1-2008", also known as "POSIX.1-2008)."
POSIX.1-2008
 In 2008, most parts of POSIX were combined into a single standard "(IEEE Std 1003.1-2008", also known as "POSIX.1-2008)."
One
 The POSIX specifications for Unix-like operating systems originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents (POSIX.1, POSIX.2, etc.).
19
The POSIX specifications for Unix-like operating systems originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents
POSIX.1, POSIX.2, etc.
The POSIX specifications for Unix-like operating systems originally consisted of a single document for the core programming interface, but eventually grew to 19 separate documents (POSIX.1, POSIX.2, etc.)