History of Unix

The history of Unix dates back to the mid-1960s, when the Massachusetts Institute of Technology, AT&T Bell Labs, and General Electric were jointly developing an experimental time-sharing operating system called Multics for the GE-645 mainframe.
Multics introduced many innovations, but also had many problems. Bell Labs, frustrated by the size and complexity of Multics but not its aims, slowly pulled out of the project. Their last researchers to leave Multics – among them Ken Thompson, Dennis Ritchie, Doug McIlroy, and Joe Ossanna – decided to redo the work, but on a much smaller scale. A
PDF
/ref>

In 1979, Ritchie described the group's vision for Unix:

1960s

In the late 1960s, Bell Labs was involved in a project with MIT and General Electric to develop a time-sharing system, called Multiplexed Information and Computing Service (Multics), allowing multiple users to access a mainframe simultaneously. Dissatisfied with the project's progress, Bell Labs management ultimately withdrew.

Ken Thompson, a programmer in the Labs' computing research department, had worked on Multics. He decided to write his own operating system. While he still had access to the Multics environment, he wrote simulations for the new file and paging system on it. He also programmed a game called ''Space Travel'', but it needed a more efficient and less expensive machine to run on, and eventually he found a little-used Digital Equipment Corporation PDP-7 at Bell Labs. On the PDP-7, in 1969, a team of Bell Labs researchers led by Thompson and Ritchie, including Rudd Canaday, implemented a hierarchical file system, the concepts of computer processes and device files, a command-line interpreter, and some small utility programs, modeled on the corresponding features in Multics, but simplified. The resulting system, much smaller and simpler than Multics, was to become Unix. In about a month's time, in August 1969, Thompson had implemented a self-hosting operating system with an assembler, editor and shell, using a GECOS machine for bootstrapping. "In August 1969, Ken Thompson's wife Bonnie took their year-old son on a trip to California to show off to their families. As a temporary bachelor, Ken had time to work. 'I allocated a week each to the operating system, the shell, the editor and the assembler e told me.. and during the month she was gone, it was totally rewritten in a form that looked like an operating system'"

Douglas McIlroy then ported TMG compiler-compiler to PDP-7 assembly, creating the first high-level language running on Unix. Thompson used this tool to develop the first version of his B programming language.

1970s

The new operating system was initially without organizational backing, and also without a name. At this stage, the new operating system was a singletasking operating system, not a multitasking one such as Multics. The name ''Unics'' (Uniplexed Information and Computing Service, pronounced as "eunuchs"), a pun on ''Multics'' (Multiplexed Information and Computer Services), was initially suggested for the project in 1970. Brian Kernighan claims the coining for himself, and adds that "no one can remember" who came up with the final spelling ''Unix''. Dennis Ritchie and Doug McIlroy also credit Kernighan.

When the Computing Sciences Research Center wanted to use Unix on a machine larger than the PDP-7, while another department needed a word processor, Thompson and Ritchie added text processing capabilities to Unix and received funding for a PDP-11/20. For the first time in 1970, the Unix operating system was officially named and ran on the PDP-11/20. A text-formatting program called roff and a text editor were added. All three were written in PDP-11/20 assembly language. Bell Labs used this initial text-processing system, consisting of Unix, roff, and the editor, for text processing of patent applications. Roff soon evolved into troff, the first electronic publishing program with full typesetting capability.

As the system grew in complexity and the research team wanted more users, the need for a manual grew apparent. The '' UNIX Programmer's Manual'' was published on 3 November 1971; commands were documented in the "man page" format that is still used, offering terse reference information about usage as well as bugs in the software, and listing the authors of programs to channel questions to them.

After other Bell Labs departments purchased DEC PDP-11s, they also chose to run Unix instead of DEC's own operating system. By Version 4 it was widely used within the laboratory and a Unix Support Group was formed, helping the operating system survive by formalizing its distribution.

In 1973, Version 4 Unix was rewritten in the higher-level language C, contrary to the general notion at the time that an operating system's complexity and sophistication required it to be written in assembly language. The C language appeared as part of Version 2. Thompson and Ritchie were so influential on early Unix that McIlroy estimated that they wrote and debugged about 100,000 lines of code that year, stating that "heir namesmay safely be assumed to be attached to almost everything not otherwise attributed". Although assembly did not disappear from the man pages until Version 8, the migration to C suggested portability of the software, requiring only a relatively small amount of machine-dependent code to be replaced when porting Unix to other computing platforms. Version 4 Unix, however, still had considerable PDP-11-dependent code and was not suitable for porting. The first port to other platform was made five years later (1978) for Interdata 8/32.

The Unix operating system was first presented formally to the outside world at the 1973 Symposium on Operating Systems Principles, where Ritchie and Thompson delivered a paper. This led to requests for the system, but under a 1956 consent decree in settlement of an antitrust case, the Bell System (the parent organization of Bell Labs) was forbidden from entering any business other than "common carrier communications services", and was required to license any patents it had upon request. Unix could not, therefore, be turned into a product. Bell Labs instead shipped the system for the cost of media and shipping. Ken Thompson quietly began answering requests by shipping out tapes and disks, each accompanied by according to legend a note signed, "Love, Ken".

In 1973, AT&T released Version 5 Unix and licensed it to educational institutions, and licensed 1975's Version 6 to companies for the first time. While commercial users were rare because of the cost, the latter was the most widely used version into the early 1980s. Anyone could purchase a license, but the terms were very restrictive; licensees only received the source code, on an as-is basis. The licenses also included the machine-dependent parts of the kernel, written in PDP-11 assembly language. Copies of the '' Lions' Commentary on UNIX 6th Edition, with Source Code'' circulated widely, which led to considerable use of Unix as an educational example. The first meeting of Unix users took place in New York in 1974, attracting a few dozen people; this would later grow into the USENIX organization. The importance of the user group stemmed from the fact that Unix was entirely unsupported by AT&T.

Versions of the Unix system were determined by editions of its user manuals; for example, "Fifth Edition UNIX" and "UNIX Version 5" have both been used to designate the same version. The Bell Labs developers did not think in terms of "releases" of the operating system, instead using a model of continuous development, and sometimes distributing tapes with patches (without AT&T lawyers' approval). Development expanded, adding the concept of pipes, which led to the development of a more modular code base, and quicker development cycles. Version 5, and especially Version 6, led to a plethora of different Unix versions both inside and outside Bell Labs, including PWB/UNIX and the first commercial Unix, IS/1.

Unix still only ran on DEC systems. As more of the operating system was rewritten in C (and the C language extended to accommodate this), portability also increased; in 1977, Bell Labs procured an Interdata 8/32 with the aim of porting Unix to a computer that was as different from the PDP-11 as possible, making the operating system more machine-independent in the process. Unix next ran as a guest operating system inside a VM/370 hypervisor at Princeton. Simultaneously, a group at the University of Wollongong ported Unix to the similar Interdata 7/32. Target machines of further Bell Labs ports for research and AT&T-internal use included an Intel 8086-based computer (with custom-built MMU) and the UNIVAC 1100.

In May 1975, ARPA documented the benefits of the Unix time-sharing system which "presents several interesting capabilities" as an ARPA network mini-host in RFC 681.

In 1978, UNIX/32V was released for DEC's then new VAX system. By this time, over 600 machines were running Unix in some form. Version 7 Unix, the last version of Research Unix to be released widely, was released in 1979. In Version 7, the number of system calls was only around 50, although later Unix and Unix-like systems would add many more:

A microprocessor port of Unix, to the LSI-11, was completed in 1978, and an Intel 8086 version was reported to be "in progress" the same year. The first microcomputer versions of Unix, and Unix-like operating systems like Whitesmiths' Idris, appeared in the late 1970s.

1980s

Bell developed multiple versions of Unix for internal use, such as CB UNIX (with improved support for databases) and PWB/UNIX, the "Programmer's Workbench", aimed at large groups of programmers. It advertised the latter version, as well as 32V and V7, stating that "more than 800 systems are already in use outside the Bell System" in 1980, and "more than 2000" the following year. Research Unix versions 8, 9, and 10 were developed through the 1980s but were only released to a few universities, though they did generate papers describing the new work. This research focus then shifted to the development of Plan 9 from Bell Labs, a new portable distributed system.

Because the company widely and inexpensively licensed Unix, by the early 1980s thousands of people used Unix at AT&T and elsewhere, and as computer science students moved from universities into companies they wanted to continue to use it. Observers began to see Unix as a potential universal operating system, suitable for all computers. Less than 20,000 lines of code almost all in C composed the Unix kernel as of 1983, and more than 75% was not machine-dependent. By that year Unix or a Unix-like system was available for at least 16 different processors and architectures from about 60 vendors; ''BYTE'' noted that computer companies "may support other peratingsystems, but a Unix implementation always happens to be available", and that DEC and IBM supported Unix as an alternative to their proprietary operating systems.

Microcomputer Unix became commercially available in 1980, when Onyx Systems released its Zilog Z8000-based C8002 and Microsoft announced its first Unix for 16-bit microcomputers called Xenix, which the Santa Cruz Operation (SCO) ported to the 8086 processor in 1983. Other companies began to offer commercial versions of Unix for their own minicomputers and workstations. Many of these new Unix flavors were developed from the System V base under a license from AT&T; others were based on BSD. One of the leading developers of BSD, Bill Joy, went on to co-found Sun Microsystems in 1982 and created SunOS for its workstations.

AT&T announced UNIX System III based on Version 7, and PWB in 1981. Licensees could sell binary sublicenses for as little as , which observers believed indicated that AT&T now viewed Unix as a commercial product. This also included support for the VAX. AT&T continued to issue licenses for older Unix versions. To end the confusion between all its differing internal versions, AT&T combined them into UNIX System V Release 1. This introduced a few features such as the vi editor and curses from the Berkeley Software Distribution of Unix developed at the University of California, Berkeley Computer Systems Research Group. This also included support for the Western Electric 3B series computers. AT&T provided support for System III and System V through the Unix Support Group (USG), and these systems were sometimes referred to as USG Unix.

In 1983, the U.S. Department of Justice settled its second antitrust case against AT&T, causing the breakup of the Bell System. This relieved AT&T of the 1956 consent decree that had prevented the company from commercializing Unix. AT&T promptly introduced Unix System V into the market. The newly created competition nearly destroyed the long-term viability of Unix, because it stifled the free exchanging of source code and led to fragmentation and incompatibility. The GNU Project was founded in the same year by Richard Stallman.

Since the newer commercial UNIX licensing terms were not as favorable for academic use as the older versions of Unix, the Berkeley researchers continued to develop BSD as an alternative to UNIX System III and V. Many contributions to Unix first appeared in BSD releases, notably the C shell with job control (modelled on ITS). Perhaps the most important aspect of the BSD development effort was the addition of TCP/IP network code to the mainstream Unix kernel. The BSD effort produced several significant releases that contained network code: 4.1cBSD, 4.2BSD, 4.3BSD, 4.3BSD-Tahoe ("Tahoe" being the nickname of the Computer Consoles Inc. Power 6/32 architecture that was the first non-DEC release of the BSD kernel), Net/1, 4.3BSD-Reno (to match the "Tahoe" naming, and that the release was something of a gamble), Net/2, 4.4BSD, and 4.4BSD-lite. The network code found in these releases is the ancestor of much TCP/IP network code in use today, including code that was later released in AT&T System V UNIX and early versions of Microsoft Windows. The accompanying Berkeley sockets API is a de facto standard for networking APIs and has been copied on many platforms.

During this period, many observers expected that UNIX, with its portability, rich capabilities, and support from companies like DEC and IBM, was likely to become an industry-standard operating system for microcomputers. Citing its much smaller software library and installed base than that of MS-DOS and the IBM PC, others expected that customers would prefer personal computers on local area networks to Unix multiuser systems. Microsoft planned to make Xenix MS-DOS's multiuser successor; by 1983 a Xenix-based Altos 586 with 512 KB RAM and 10 MB hard drive cost . ''BYTE'' reported that the Altos "under moderate load approaches DEC VAX performance for most tasks that a user would normally invoke", while other computers from Sun and MASSCOMP were much more expensive but equaled the VAX. The magazine added that both PC/IX and Venix on the IBM PC outperformed Venix on the PDP-11/23. uNETix, a commercial microcomputer Unix, implemented the first Unix color windowing system.

Thompson and Ritchie were given the Turing Award in 1983 for their work on Unix.

In 1986, '' Computerworld'' wrote that "Until very recently, almost no one associated Unix with corporate data processing. ..the operating system traveled almost exclusively in academic and technical circles ... But now — almost entirely because of strenuous efforts by AT&T — some people are beginning to perceive Unix as a viable option for large commercial installations." Unix became commercially available for the mainframe via Amdahl UTS in 1981, and now IBM started offering Unix as IX/370 and VM/IX. The total installed base of Unix, however, remained small at some 230,000 machines.

Despite its academic reputation ''InfoWorld'' stated in 1989, "Until recently, Unix conjured up visions of long-haired bearded technoids stuck in the bowels of an R&D lab, coding software until the wee hours of the morning" the increasing power of microcomputers in the late 1980s, and in particular the introduction of the 32-bit Intel 80386

HOME


Content is Copyleft
Website design, code, and AI is Copyrighted (c) 2014-2017 by Stephen Payne


Consider donating to Wikimedia



As an Amazon Associate I earn from qualifying purchases