Evolution of UNIX
Evolution of UNIX
Bill Stewart
December 01, 2011
Marshall University
CIS155: UNIX Operating System

In the late 1960's computers worked entirely different than the ones that we do our work on every day. They did not talk to each other and programs written for use on one computer did not work on another. Today’s basic cell phone has more processing power and memory capabilities as computers from the 1960's. The few operating systems available at that time performed very limited tasks and were exclusive to the computer it was written on. In other words when one upgraded to a newer computer, the operating system and all data that you wanted transferred from the old computer had to be rewritten on the newer model. In 1965 a joint effort of Bell Labs, MIT and GE began to develop a general computer operating system that was named the MULTICS (Multiplexed Information and Computing Service) mainframe timesharing system. The MULTICS project was being funded by the Department of Defense Advanced Research Projects Agency. The goal of the MULTICS group was to develop a feature-packed information utility that would allow timesharing of mainframe computers by large communities of users. It was also designed to be able to support multilevels of security with the military in mind. When Bell Labs joined the project their goal was to obtain a timesharing system for use by members of the technical staff at Bell Labs. When the planned time had passed and MULTICS was not ready to use, it was clear that there was a lot more work to do, Bell Labs felt they had no choice than to opt out in 1969 (Ward 2009). Even though Bell Labs withdrew from the MULTICS project, two programmers from Bell Labs, Ken Thompson and Dennis Ritchie, decided to continue working to develop a usable operating system (Peek 2002). They saw great value in the communal environment enabled by a multi-user computer system and started looking for a way to preserve its capability. While working on the MULTICS project, Thompson wrote a game called Space Travel which simulated the motion of the planets in the solar system and allowed a player to cruise around the planets and even land on the planets (Ritchie 1980). Thompson rewrote the program to run on a GE 635 computer but due to the high cost of using that computer he found a seldom used PDP-7 computer with a much better display terminal and rewrote the program once again. Thompson had many ideas that he wanted to try to keep developing the operating system and the use of the PDP-7 computer allowed him to keep working on the program (Raymond 2003). Once it became known that Bell Labs was withdrawing from the Multics project, Thompson still wanted to solve two problems: to create an operating system and to develop an environment in which to do future work. In the late stages of the Bell Labs involvement in Multics, Thompson, Ritchie, and a few others discussed their ideas and recorded them through a Bell Labs dictation service for later use. Now that Thompson had the PDP-7 machine for Space Travel, he used the notes to develop the basis for what would become UNIX (Raymond 2003). They had three main goals in developing their operating system: a system that would be simple and elegant, written in a high level language instead of assembly language, and allow re-use of code (Ward 2009). In August 1969 during a month long absence of his wife and son, Ken Thompson wrote what was to become UNIX, originally named UNICS, a play on Multics, but was later changed to UNIX, by spending one week each on the operating system, a shell, an editor, and an assembler. Over the next few years the operating system was being developed. In 1973 Dennis Ritchie wrote the high-level programming language C which was based on Thompson’s B language. Thompson then rewrote UNIX in the C language allowing portability across computer environments (Nemeth 2011). The migration from assembly language to the higher-level language C marked in portable software that called for only a rather small amount of machine dependent code to be replaced when porting UNIX to other computing platforms. The simplicity of the code allowed for many developments since one could rewrite the code for a single tool that performed a single function in UNIX without having to rewrite the entire program. This led to many additions for the new operating system, including the biggest addition, the pipe command which was developed in 1973 by Doug McIlroy. The pipe command allowed a user to pass the output of one program to another and has essentially been copied by all the UNIX variants, such as Linux, DOS, and Windows (Nemeth 2011). In 1975, UNIX version 6 was released to the outside world. By 1977, more than 500 sites were running UNIX (Ritchie 1980). Word about UNIX began to spread it caught fire among the academic community. AT&T helped this grassroots movement by giving the software away for free at the time (Ward 2009). When version 7 was released in 1979, the UNIX licenses prohibited universities from using the UNIX source code in their courses. This became a problem because Bill Joy, a programmer at the University of California Berkeley, already had a copy of UNIX and began using it to develop a Pascal compiler and text editor. UC Berkeley made modifications which resulted in the second major branch of UNIX called Berkeley Software Distribution (BSD). Joy began selling copies for $50. Eventually AT&T and Bill Joy’s Sun Microsystems formed an alliance that would lead to a unified product (Ward 2009). Since developers anywhere could customize the UNIX source code to fit their needs, many variants of UNIX were being developed (Ward 2009). In 1991 a 21 year old second year Computer Science student at the University of Helsinki, Linus Torvalds, loved to tinker with computers and push them to their limits. Linus realized all that there was a need for an industry strength operating system that could meet the demands of the professionals (Hasan 2005). Thus began the infancy of LINUX. In early 1991 Torvalds purchased an IBM-compatible personal computer with a 33MHz Intel 386 processor and a huge 4MB of memory. This processor greatly appealed to him because it represented a tremendous improvement over earlier Intel chips.
However Torvalds was disappointed with the MS-DOS operating system that came with it. MS-DOS hadn't evolved enough to even begin to take advantage of the vastly improved capabilities of the 386 chip; Torvalds preferred the more powerful and stable UNIX operating system that he had become accustomed to using on the university's computers. Torvalds decided to create a new operating system from scratch that was based on both MINIX and UNIX (Marti 2009). This creation, Torvalds named Linux, was released in September 1991. As Linux was released in September 1991 enthusiasm gathered around this new kid on the block and codes were downloaded, tested, tweaked, and returned to Torvalds (Marti 2009). Version 0.02 came on October 5th, 1991. The development of Linux is one of the most prominent examples of free and open source software collaboration. Amazing things began to happen with Linux. Besides the PC, Linux was ported to many different platforms. Linux was programmed to run 3Com's handheld Palm Pilot computer. In April 1996, researchers at Los Alamos National Laboratory used Linux to run 68 PCs as a single parallel processing machine to simulate atomic shock waves. But unlike other Supercomputers costing a fortune, it was rather cheap. The do-it-yourself supercomputer cost only $152,000 about one tenth the price of a comparable commercial machine. It reached a peak speed of 19 billion calculations per second, making it the 315th most powerful supercomputer in the world. Three months later it still didn't have to be rebooted (Hasan 2005).

Linux got another big boost in the late 1990s when competitors of Microsoft began taking it seriously. Oracle, Intel, Netscape, Corel and others announced plans to support Linux as an inexpensive alternative to Microsoft Windows. Perhaps the biggest force for Linux adoption in the corporate world has been IBM's official blessing and massive support. Linux is finally reaching the point where it is suitable for use as a low cost alternative on the desktop and notebook computers of ordinary people who have little understanding of (or interest in) computers but who need them for their work and leisure activities. Proving all the warning and prophecies of the skeptics wrong, Linux has completed a decade of development. Today, Linux is one of the fastest growing operating systems in the history (Hasan 2005). As with Thompson and Ritchie commitment to UNIX, Torvalds phenomenal success is undoubtedly due to his brilliance and dedication. Also important Torvalds made a series of wise strategic decisions, not only about the technical aspects of the operating system but also about how it would be developed and licensed, including that very early decision to make Linux free software. In summary UNIX is still used today by many corporations. Although most people don’t realize this UNIX is the backbone of many telecommunications systems including the maintenance, operating and administrations systems (Nemeth 2011). It also helps monitor electronic switches and fiber optic transmission systems, as well as billing customers for their telephone use. Many research facilities, universities, and programmers use UNIX primarily due to its multitasking and multiuser capabilities as well as its large library of application software (Nemeth 2011). After decades of use, the UNIX computer operating system is still respected as one of the most powerful, versatile, and flexible operating systems in the computer world. Its popularity is attributed to many factors, including its ability to run a wide assortment of computers from micro to supercomputers and its manageability, all of which has led its acceptance by many computer manufacturers. Linux, as a leader in server operating systems, runs the 10 fastest supercomputers in the world. More than 90% of today's supercomputers run some variant of Linux (Nemeth 2011). Ken Thompson and Dennis Ritchie could not have envisioned the journey they embarked in 1965 due to their diligent work and dedication to the UNIX shell and operating system. They have made the possibilities in the computing world endless. The end does not appear to be in sight for many years to come.

References
Hasan, R. (n.d.). History of Linux. Department of Computer Science - University of Illinois at Urbana-Champaign. Retrieved December 7, 2011, from http://netfiles.uiuc.edu/rhasan/linux
Marti, D. (2009, April 22). Linus on Linux: The Linus Torvalds Interview | Linux Magazine. Linux Magazine | Open Source, Open Standards. Retrieved December 10, 2011, from http://www.linux-mag.com/id/7313/
Nemeth, E. (2011). UNIX and Linux system administration handbook (4th ed.). Upper Saddle River, NJ: Prentice Hall.
Peek, J. D. (2002). Learning the UNIX operating system (5th ed.). Sebastopol, CA: O'Reilly.
Raymond, E. (2004). The Art of Unix programming. Boston: Addison-Wesley.
Ritchie, D. (1980, Sep. - Oct.). The Evolution of the Unix Time-sharing System. Computer Science, 79, 77-93.
Ward, M. (2009, August 20). 40 years of Unix. BBC News - Technology. Retrieved December 10, 2011, from http://news.bbc.co.uk/2/hi/technology/8205976.stm