The Unix revolution—thank you, Uncle Sam?

Why did the Unix operating system expand so quickly in the 1970s and 1980s?

This November, the Unix community has another notable anniversary to celebrate: the 40th birthday of the first edition of Ken Thompson and Dennis Ritchie's Unix Programmers Manual,
released in November 1971. Producing the document was no easy task,
because at that point the Unix operating system grew by the week;
budding aficionados added new commands and features to the system on a
regular basis.

"The rate of change of the system is so great that a dismayingly
large number of early sections [of the text] had to be modified while
the rest were being written," Thompson and Ritchie noted in their
introduction. "The unbounded effort required to stay up-to-date is best
indicated by the fact that several of the programs described were
written specifically to aid in preparation of this manual!"

That's why Unix timelines are fun to read—they give a sense of how quickly the system collaboratively evolved. But some of them either skip or mention without explanation
a government decision that, in retrospect, paved the way not only for
Unix, but perhaps for the open source movement as well: the 1956 Consent
Decree between the United States Department of Justice and AT&T.

That crucial decision didn't exactly force AT&T to share Unix with the world, but it made the decision much easier.

Dangerous program!

The Unix operating system was born during the most creative point in
any technology story: failure. One day in 1969, an administrator showed
up with bad news at the fifth floor of AT&T's Bell Telephone
Laboratories (BTL) in Murray Hill, New Jersey. Bell was shutting down
The Multics Project, he explained. (Multics was BTL's first attempt to
create a time-sharing system that would allow many users to access and
work on a computing network simultaneously.)

For the project staff, the news came as a blow. This was a "traumatic
change... The toy was gone... there was a clear lack of momentum," one
staffer recalled. But the cold truth was that Multics did not work.

"Multics couldn't even accommodate three users efficiently," writes Unix historian Peter Salus in his engaging book A Quarter Century of Unix. "Computer research at BTL was in the doldrums."

Undaunted, BTL programmers Thompson, Ritchie, and others informally
soldiered on with a smaller-scale version of the concept on a PDP-7
minicomputer. The standard version of Unix history notes that Ken Thompson ran his Space Travel
game program on Multics and wanted to keep it around. The new project,
however, was about a lot more than that. By telling the suits upstairs
that they were developing text editing software, the group even managed
to wheedle a superior PDP-11/20 machine from Bell.

"We knew there was a scam going on—we'd promised a word processing
system, not an operating system," Ritchie later admitted. The team did
deliver Unix as a text processing application to the Patent Department,
but an operating system was what Bell eventually got—albeit a rough one
at first.

"Program development generally occurred out-of-hours," a programmer
subsequently explained to Salus. "The terminals on the development
machine were in a common room and when several people were at work, one
would call out 'dangerous program!' before executing a new a.out file (the default output file from the linking editor). This allowed others to save their editor-files quickly (and often)."

By the early 1970s, the basic components and concepts associated with
Unix were established. Written in the C programming language, Unix
offered a tight array of efficient "tools" or applications, whose text
streams could be "piped" from one program to another.

"Unix now had a language all its own," Salus notes. "It had a
philosophy, an ethos. It had a relatively small group of devoted users
on a handful of AT&T Bell sites." The question now was what AT&T
would do with the new OS.

Ready to do our part

Almost twenty-five years before the first Unix Programmers Manual was
released, the United States Department of Justice announced that it was
pursuing an antitrust action against AT&T, which controlled most of
the nation's telephone network. The 73-page complaint was released in
1949, just after Harry Truman was reelected to the White House. It
charged AT&T with running a price-fixing conspiracy. The document
also accused AT&T subsidiary Western Electric of monopolizing the
market for telephones.

The DoJ demanded that AT&T be divested of the device-making
company, but the Korean War exploded a year later. AT&T responded by
wrapping itself in the American flag, noting its role as a defense
contractor and its management of Sandia Labs.

"The Bell System has always stood ready to do its part in the
national defense by undertaking work for which it is particularly
fitted," AT&T's president wrote to David Lilienthal, Chair of the
Atomic Energy Commission. But, he added, "this situation in relation to
the antitrust suit made us question with you whether it would in fact be
desirable in the national interest for us to undertake this project."

By 1951, AT&T had the Pentagon on its side. "It is clear to me
that the mobilization effort will be impeded by pressing this suit,"
warned the Secretary of Defense that year. He asked that the DoJ action
be postponed "while the present situation continues to exist."

A year later Truman was gone, replaced by Dwight Eisenhower. AT&T
pressed Eisenhower to dismiss the antitrust suit. In the summer of
1953, the administration's new Attorney General Herbert Brownell met
with the telco's General Counsel T.B. Price.

At the meeting, Brownell asked AT&T to think over a voluntary
settlement. "He asked me whether, if we reviewed our practices, we would
be able to find things we are doing which were once considered entirely
legal, but might now be in violation of the antitrust laws or
questionable in that respect," the AT&T representative later
recalled. The new attorney general also assured AT&T that "if a
settlement was worked out he could get the President's approval in 5
minutes."

Such a list of things was submitted, and in 1956 AT&T and the
government entered into what was called the "Consent Decree" on the
matter.

Keeping the beast quiet

Central to the consent decree was a provision that Bell Systems
patents be licensed to competitors on request. AT&T had 8,600
patents cross-licensed to General Electric, RCA, and Westinghouse. These
were now to be licensed without royalty payments to applicants other
than the aforementioned companies, and future AT&T patents had to be
licensed to applicants at "reasonable royalty" rates, and necessary
technical information had to be shared.

Equally important was a requirement that AT&T stay out of "any
business other than the furnishing of common carrier communications
services." The decree also enjoined Western from "any business not of a
character or type engaged in by Western or its subsidiaries for
Companies of the Bell System."

As telecommunications historian Gerald Brock notes, this deal didn't
interrupt the big picture. It allowed AT&T to keep Western Electric
and its monopoly, but it made the telecom much more dependent on
regulatory decisions. AT&T "lost the freedom to enter other markets
when it saw that advantage," Brock observes.

The agreement also made AT&T much more circumspect about
innovations coming out of Bell Labs. "The lawyers at BTL were
conservative," Salus explains. "There was no sense in aggravating the
beast that was the Justice Department. No business but phones and
telegrams."

Pay in advance

It was in this context that Ken Thompson presented his work to the
Fourth Association for Computing Machinery Symposium on Operating
Systems Principles in October of 1973. Suddenly "a trickle of requests"
for more information started coming in from sites "that had nothing at
all to do with BTL, AT&T, or Western Electric," Salus writes. The
publication of the paper "started a flood," especially from universities
looking for affordable software.

AT&T's response to this windfall was caution. "The company took a
very self-constricting view of the decree," one Bell programmer later
explained, and so worried about Unix. In fact, AT&T management
"didn't understand what we had in Unix," another administrator later
conceded.

Thus, "rather than irritating the great judicial dragon," AT&T's
legal department decided to license Unix patents too, "but would make it
clear that it had no intention of pursing software as a business." A
retrospective talk about AT&T/Unix marketing policy given ten years
later described the Bell Unix terms:

No advertising

No support

No bug fixes

Payment in advance

This did not daunt university and government systems operators. The
Patent Licensing office at Bell in 1970 usually negotiated four or five
deals a year. By 1974 "the office staff were, simply, overwhelmed by the
number of requests for Unix licenses," Salus explains. It only got
worse "when the first military and then commercial enterprises asked for
licenses."

Did AT&T's refusal to provide technical support hurt Unix? Quite
the opposite, argues Salus. Instead, the policy had an "immediate
effect: it forced the users to share with one another. They shared
ideas, information, programs, bug fixes, and hardware fixes."

Unix was a "godsend" for university computer divisions, observes
computer historian Paul Ceruzzi. For a nominal license fee they could
obtain the source code, run it through a C compiler, and farm debugging
and development out to cheap graduate student labor. "By contrast, most
computer vendors guarded source code as their family jewels, seldom gave
it out, and did all they could to lock a customer into their products."

In other words, AT&T's Unix policies helped Unix become the
operating system that we've all come to know, and, if not love,
understand as empowered by a philosophy that also informs the "open
source" movement of our time.

Not everyone agrees with this interpretation. Timelines and histories
about open source rarely or only briefly mention the Consent Decree or
its impact on AT&T and Unix. "In the 1970s AT&T distributed
early versions of UNIX at no cost to government and academic
researchers," Wikipedia notes, "but these versions did not come with permission to redistribute or to distribute modified versions, and were thus not free software in the modern meaning of the phrase."

It's hard to imagine, however, that the early Unix experience didn't
help create expectations that paved the way for open source. In any
event, the 1956 Consent Decree probably doesn't get too many birthday
notices on Facebook. For the record, this year it turns 55.

Further reading

Peter H. Salus, A Quarter Century of UNIX

Gerald W. Brock, The Telecommunications Industry

Paul E. Cerruzi, A History of Modern Computing

Matthew Lasar
Matt writes for Ars Technica about media/technology history,
intellectual property, the FCC, or the Internet in general. He teaches
United States history and politics at the University of California at
Santa Cruz.