A Little History of UNIX

Until UNIX came on the scene, operating systems where designed with a particular machine in mind. They were invariably written in a low level language (like assembler, which uses humanly unfriendly code). The systems were fast but were restricted to the hardware they were designed for. Programs designed for one system simply wouldn't run on another. That was the status of the computer industry when Ken Thompson and Dennis Ritchie, of AT&T fame, authored the UNIX system for their own use.

In 1969, AT&T withdrew its team from the MULTICS project, which was engaged in the development of a flexible operating system that would run continuously and be used remotely. Thompson and Ritchie then designed and built a small system with an elegant file system, a command interpreter (the shell), and a set of utilities. To make UNIX portable, they rewrote the entire system in the C language that was invented by Ritchie himself. C is a high-level language, and programs coded in C run on all hardware. Portability became one of the strong features of UNIX.

Berkeley: The Second School

An U.S. government law (subsequently revoked) prevented AT&T from selling computer software. The company had no option but to distribute the product to academic and research institutions at a nominal fee, but it came without any support. From the AT&T product, the University of California, Berkeley (UCB), created a UNIX of its own. They called it BSD UNIX (BSD-Berkeley Software Distribution). Both of these versions became quite popular worldwide, especially in universities and engineering circles. Later, UCB gave up all development work on UNIX.

Berkeley filled in the gaps left behind by AT&T, and then later decided to rewrite the whole operating system in the way they wanted. They created the standard editor of the UNIX system (vi) and a popular shell (C shell). Berkeley also created a better file system, a more versatile mail feature, and a better method of linking files (symbolic links). Later, they also offered with their standard distribution a networking protocol software (TCP/IP) that made the Internet possible. Like AT&T, they also offered it practically free to many companies.

UNIX Gets Fragmented

Even though UNIX was written by programmers for programmers, its inherent strengths found favor within business circles. Sun used the BSD System as a foundation for developing their own brand of UNIX (then SunOS). Today, their version of UNIX is known as Solaris. Others developed their own brands: IBM had AIX, HP offered HP-UX, while DEC produced Digital UNIX-and now Tru64 UNIX. Then the Linux wave arrived, and most of these vendors began to offer Linux too. Today, most supercomputers run UNIX, and handheld devices increasingly use Linux.

As each vendor modified and enhanced UNIX to create its own version, the original UNIX lost its identity as a separate product. The BSD releases were much different from the AT&T System V releases, and the incompatibilities steadily mounted. Finally, AT&T took it upon themselves to unify many of these flavors into its last release- System V Release 4 (SVR4). Shortly thereafter, AT&T sold its UNIX business to Novell, who later turned over the UNIX trademark to a standards body called X/OPEN, now merged with The Open Group.

The Internet

Even before the advent of SVR4, big things were happening in the U.S. Defense Department. DARPA, a wing of the department, engaged several vendors to develop a reliable communication system using computer technology. Through some brilliant work done by Vinton Cerf and Robert Kahn, DARPA's ARPANET network was made to work using packet-switching technology. In this technology, data is split into packets, which can take different routes and yet be reassembled in the right order. This was the birth of TCP/IP-a set of protocols (rules) used by the Internet for communication.

DARPA commissioned UCB to implement TCP/IP on BSD UNIX. ARPANET converted to TCP/IP in 1983, and in the same year, Berkeley released the first version of UNIX which had TCP/IP built-in. The computer science research community were all using BSD UNIX, and the network expanded like wild fire. The incorporation of TCP/IP into UNIX and its use as the basis of development were two key factors in the rapid growth of the Internet (and UNIX).

The Windows Threat

In the meantime, Microsoft was doing great things with Windows-a graphical user interface (GUI) that uses the mouse rather than arcane and complex command options to execute a job. Options could be selected from drop-down menu boxes and radio buttons, which made handling some of the basic operating system functions easier. Windows first swept the desktop market (with Windows 3.1/95/98) and then made significant inroads into the server market (with Windows NT/2000) which had been long dominated by UNIX.

When UNIX badly needed a Windows-type interface for its survival, the Massachusetts Institute of Technology (MIT) introduced X Window-the first windowing system for UNIX. X Window has many of the important features of Microsoft Windows plus a lot more. Every flavor of UNIX now has X along with a host of other tools that can not only handle files and directories but also update the system's configuration files.