In 1960s, Honeywell in partnership with Bell Laboratories started working on the Multics operating system.
In 1969, Bell Laboratories dropped out of the project due to the increasing complexity of the project and the lack of progress
1969 → In reaction to this unpleasant experience, a group of Bell Labs researchers - Ken Thompson, Dennis Ritchie, Doug McIlroy and Joe Ossana began working on a simpler operating system for a digital equipment corporation PDP-7 computer, written entirely in machine language.
Many of the ideas in the new system like hierarchical file system and the notion of a user-level process were borrowed from Multics
In 1970, Brian Kernighan dubbed the new system Unix as a pun on the word - Multics.
The kernel of Unix was rewritten in C in 1973.
Unix was announced to the outside world in 1974.
About POSIX
In mid 1980s, different vendors started coming up with their own versions of Unix to differentiate themselves.
These versions, however, were often incompatible with each other.
To combat this trend, IEEE sponsored an effort to standardise Unix. This was dubbed as POSIX by Richard Stallman
This resulted in a family of standards known as Posix standards.
It covered issues such as C language interface for Unix system calls, shell programs and utilities, threads, and network programming
Recent developments (Standard Unix specification)
Recently, a separate standard effort has started known as Standard Unix Specification
It has joined hands with Posix to create a single, unified standard for Unix systems.