The Art of Unix Programming

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Origins and history of Unix, 1969-1995

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Origins and history of Unix, 1969-1995

Genesis: 1969-1971

Unix was born in 1969 out of the mind of a computer scientist at Bell Laboratories, Ken Thompson. Thompson had
been a researcher on the pioneering MULTICS project, an attempt to create an 鈥榠nformation utility鈥

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The PDP-7.

The full origin story is told in [Ritchie79] from the point of view of Thompson's first collaborator Dennis Ritchie,

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the man who would become known as the co-inventor of Unix and the inventor of the C language. Dennis Ritchie,
Douglas McIlroy and a few colleagues had become used to interactive computing under MULTICS and did not
want to lose that capability. Thompson's PDP-7 operating system offered them a lifeline.

Ritchie observes: 鈥淲hat we wanted to preserve was not just a good environment in which to do programming, but a
system around which a fellowship could form. We knew from experience that the essence of communal computing,
as supplied by remote-access, time-shared machines, is not just to type programs into a terminal instead of a
keypunch, but to encourage close communication.鈥

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interpreted language called B, which had the virtue that it was small enough to run on the PDP-7. But B was not
powerful enough for systems programming, so Dennis Ritchie added data types and structures to it. The resulting C
language evolved from B beginning in 1971; in 1973 Thompson and Ritchie finally succeeded in rewriting Unix in
their new language. This was quite an audacious move at the time; system programming was done in assembler in
order to extract maximum performance from the hardware, and the very concept of a portable operating system was
barely a gleam in anyone's eye. As late as 1979, Ritchie could write 鈥淚t seems certain that much of the success of
Unix follows from the readability, modifiability, and portability of its software that in turn follows from its
expression in high-level languages.鈥

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I read the CACM paper when I was sixteen years old and was delighted by its elegance and
simplicity. I was an aspiring mathematician then, and had no idea that Unix would develop
into the theme of my professional life.



--Eric S. Raymond





After the CACM paper, research labs and universities all over the world clamored for the chance to try out Unix
themselves. Under a 1958 consent decree in settlement of an antitrust case, AT&T (the parent organization of Bell
Labs) had been forbidden from entering the computer business. Unix could not, therefore, be turned into a product
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TCP/IP and the Unix Wars: 1980-1990

The Berkeley campus of the University of California emerged early as the single most important academic hot-spot
in Unix development. Unix research had begun there in 1974, and was given a substantial impetus when Ken
Thompson taught at the University during a 1975-76 sabbatical. The first BSD release had been in 1977 from a lab
run by a then-unknown grad student named Bill Joy. By 1980 Berkeley was the hub of a sub-network of universities
actively contributing to their variant of Unix. Ideas and code from Berkeley Unix (including the vi(1) editor) were
feeding back from Berkeley to Bell Labs. The Berkeley Unix hackers also ported Unix to the hottest of the new
minicomputers, the DEC VAX.

Then, in 1980, the Defense Advanced Research Projects Agency needed a team to implement its brand new TCP/IP
protocol stack on the VAX under Unix. The PDP-10s that powered the ARPANET at that time were aging, and
indications that DEC might be forced to cancel the 10 in order to support the VAX were already in the air. DARPA
considered contracting DEC to implement TCP/IP, but rejected that idea because they were concerned that DEC
might not be responsive to requests for changes in their proprietary VAX/VMS operating system. [Libes&Ressler]

Berkeley's Computer Science Research Group was in the right place at the right time with the strongest
development tools; the result became arguably the most critical turning point in Unix's history since its invention.

Until the TCP/IP implementation was released with Berkeley 4.2 in 1983, Unix had had only the weakest
networking support. Early experiments with Ethernet were unsatisfactory. An ugly but serviceable facility called
UUCP (Unix to Unix Copy Program) had been developed at Bell Labs for distributing software over conventional
telephone lines via modem [8]. UUCP could forward Unix mail between widely separated machines, and (after
Usenet was invented in 1981) supported Usenet, a distributed bulletin-board facility that allowed users to broadcast
text messages to anywhere that had phone lines and Unix systems.

Still, the few Unix users aware of the bright lights of the ARPANET felt like they were stuck in a backwater. No
FTP, no telnet, only the most restricted remote job execution, and painfully slow links. Before TCP/IP, the Internet
and Unix cultures did not mix. Dennis Ritchie's vision of computers as a way to 鈥渆ncourage close communication鈥

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2.0 eclipsed CP/M largely because Microsoft's cofounder Paul Allen merged in Unix features including
subdirectories and pipes). There were things that seemed much more interesting going on 鈥

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To make matters worse, the big new players in the Unix market promptly committed major strategic blunders. One
was to seek advantage by product differentiation 鈥

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most widely used of the open-source scripting languages. In early 1987 the first version of the GNU C compiler
appeared, and by the end of 1987 the core of the GNU toolset was falling into place 鈥

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Meanwhile, Microsoft was making billions in the home and small-business markets that the warring Unix factions
had never found the will to address. The 1990 release of Windows 3.0 鈥