Most operating systems can be grouped into two different families. Aside from Microsoft's Windows NT-based operating systems, nearly everything else traces its heritage back to Unix.
Unix a popular multi-user, multitasking operating system developed at Bell Labs in the early 1970s. Created by just a handful of programmers, the name (pronounced YEW-nihks) was a pun based on an earlier system, Multics. UNIX was designed to be a small, flexible system used exclusively by programmers. UNIX was one of the first operating systems to be written in a high-level programming language, namely C. This meant that it could be installed on virtually any computer for which a C compiler existed. The initial release of Unix had some important design attributes that live on today.
After its breakup in 1982, AT&T began to market UNIX in earnest. It also began the long and difficult process of defining a standard version of UNIX.Due to its portability, flexibility, and power, UNIX has become a leading operating system for workstations. Historically, it has been less popular in the personal computer market.
The Unix system is composed of several components that were originally packaged together. By including the development environment, libraries, documents and the portable, modifiable source code for all of these components, in addition to the kernel of an operating system, Unix was a self-contained software system. This was one of the key reasons it emerged as an important teaching and learning tool and has had such a broad influence.
Unix has evolved as a kind of large freeware product, with many extensions and new ideas provided in a variety of versions of Unix by different companies, universities, and individuals. Bell Labs distributed the operating system in its source language form, so anyone who obtained a copy could modify and customize it for his own purposes. By the end of the 1970s, dozens of different versions of UNIX were running at various sites.
Like any history going back over 40 years, the history of Unix and its descendants is messy. To simplify things, we can roughly group Unix's descendants into two groups.
One group of Unix descendants were developed in academia. The first was BSD, an open-source, Unix-like operating system. BSD lives on today through FreeBSD, NetBSD, and OpenBSD. NeXTStep was also based on the original BSD, Apple's Mac OS X was based on NeXTStep, and iOS was based on Mac OS X. Many other operating systems, including the Orbis OS used on the PlayStation 4, are derived from types of BSD operating systems.
Richard Stallman's GNU project was also started as a reaction to AT&T's increasingly restrictive Unix software licensing terms. MINIX was a Unix-like operating system created for educational purposes, and Linux was inspired by MINIX. The Linux we know today is really GNU/Linux, as it's made up of the Linux kernel and a lot of GNU utilities. GNU/Linux isn't directly descended from BSD, but it is descended from Unix's design and has its roots in academia. Many operating systems today, including Android, Chrome OS, Steam OS, and a huge amount of embedded operating systems for devices, are based on Linux.
