The UNIX operating system is a set of programs that act as a link between the computer and the user.
The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel.
Users communicate with the kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel.
Unix was originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna.
There are various Unix variants available in the market. Solaris Unix, AIX, UP Unix and BSD are few examples. Linux is also a flavour of Unix which is freely available.
Several people can use a UNIX computer at the same time; hence UNIX is called a multiuser system.
A user can also run multiple programs at the same time; hence UNIX is called multitasking.
Unix Architecture:
Here is a basic block diagram of a UNIX system:
