Unix

Unix ( , YOO-niks; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, the development of which started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including Berkeley Software Distribution (BSD), Microsoft (Xenix), Sun Microsystems (SunOS/Solaris), HP (HP-UX), and IBM (AIX). The early versions of Unix, which are retrospectively referred to as "Research Unix", ran on computers such as the PDP-11 and VAX; Unix was commonly used on minicomputers and mainframes from the 1970s onwards. It distinguished itself from its predecessors as the first portable operating system: almost the entire operating system is written in the C programming language (in 1973), which allows Unix to operate on numerous platforms. Unix systems are characterized by a modular design that is sometimes called the "Unix philosophy". According to this philosophy, the operating system should provide a set of simple tools, each of which performs a limited, well-defined function. A unified and inode-based filesystem and an inter-process communication mechanism known as "pipes" serve as the main means of communication, and a shell scripting and command language (the Unix shell) is used to combine the tools to perform complex workflows. Version 7 in 1979 was the final widely released Research Unix, after which AT&T sold UNIX System III, based on Version 7, commercially in 1982; to avoid confusion between the Unix variants, AT&T combined various versions developed by others and released it as UNIX System V in 1983. However, as these were closed-source, the University of California, Berkeley continued developing BSD as an alternative. Other vendors...