Special Report: Early Days of Unix
ronda hauben
[ Author was TELECOM Digest ]
[ Posted on Mon, 27 Dec 1993 03:16:00 CST ]
Here is a special report I think will be of interest to telecom
readers on the forthcoming 25th anniversary of the invention of the
Unix kernel at Bell Labs in 1969.
PAT
From: ro...@umcc.umcc.umich.edu (Ronda Hauben)
Subject: Early Days of Unix - Draft for Comment
Date: 26 Dec 1993 18:48:31 -0500
Organization: UMCC, Ann Arbor, MI
I am in the process of working on the current draft and I
would appreciate any comments, suggestions, additional information,
etc. regarding the early days of unix development and the work to
develop computer science that this early work on unix represented.
Thanks.
Ronda
DRAFT
On the Evolution of Unix and the Automation
of Telephone Support Operations
(i.e. of Computer Automation)
by Ronda Hauben
Abstract:
1994 is the 25th anniversary of the invention of the UNIX kernel
at Bell Labs. The following article is a chapter in a longer
paper documenting some of the events that have contributed to
the development of a Global Computer Network in the past 25 years.
This article describes how the need to automate telephone support
operations in the U.S. in the late 1960s and the early 1970s
nourished the birth and developement of the UNIX operating
system and how academic computer science contributed to
and gained from the development of UNIX. This article is intended as a
contribution to a 25th anniversary commemoration of the significance
of the UNIX breakthrough and the lessons that can be learned for
making the next step forward.
"I don't believe UNIX is Utopia. It's just the best set of tools around."
-- Dick Haight, Unix Review, Jan. 1985, p. 117
"What does industrial computer science research consist of?....Although
work for its own sake resulting, for example, in a paper in a learned journal
is not only tolerated but welcomed, there is strong though wonderfully
subtle pressure to think about problems somehow relevant to our
corporation....Indeed, researchers love to find problems to work on;
one of the advantages of doing research in a large company is the
enormous range of puzzles that turn up....Thus, computer research
at Bell Labs has always had a considerable commitment to the world...."
-- Dennis Ritchie, "Reflections on Software Research,"
Communications of the ACM, vol 27, no. 8, August 1984, p. 759
"Bell had already gained some field support experience switching machines
and their software. Supporting a network of mini computers would be
a significantly different problem."
-- August Mohr, "The Genesis Story,"
Unix Review, Jan. 1985, p.24
"From hence it necessarily follows...Rich and Poor, Young and Old, must
must study the Art of Number, Weight, and Measure.
Sir William Petty," Political Arithmetic,"
in Collected Works, vol 1, p. 261.
During the formative years in the creation of the Arpanet, which
was to become the backbone to the Global Computer Network, there were
similar seminal developments taking place at the Bell Laboratories,
the Research and Development unit of the Bell System. These
developments were to have a significant impact on the future course of
computer science research and networking in the world. As early as
1957, Bell Labs found they needed an operating system for their
inhouse computer center which was then running lots of short batch
jobs. Describing the situation facing the Labs, Victor Vyssotsky, who
had been involved the techanical head of the Multics project at Bell
Labs and later Executive Director of Research in the Information
Systems Division of AT&T Bell Labs, explains, " We just couldn't take
the time to get them on and off the machine manually. We needed an
operating system to sequence jobs through and control machine
resources." (from "Putting Unix in Perspective", Interview with Victor
Vyssotsky, by Ned Pierce, in Unix Review, Jan. 1985, p. 59)
The BESYS operating system was created at Bell Labs to deal with
their inhouse needs. When asked by others outside the labs to make a
copy available, they did so but with no obligation to provide support.
"There was no support when we shipped a BESYS tape to somebody,"
Vyssotsky recalls, "we would answer reasonable questions over the
telephone. If they found troubles or we found troubles, we would
provide fixes." (Ibid., p. 59)
By 1964, however, the Labs was adopting third generation computer
equipment and had to decide whether they would build their own
operating system or go with one that was built outside the Labs.
Vyssotsky recounts the process of deliberation at the time, "Through a
rather murky process of internal deliberation we decided to join
forces with General Electric and MIT to create Multics," he explains.
The Labs planned to use the Multics operating system "as a mainstay
for Bell Laboratories internal service computing in precisely the way
that we had used the BESYS operating system." (Ibid., p. 59)
The collaborative project by GE, MIT and AT&T to create a computer
operating system that would be called Multics (1965-68) was to "show
that general-purpose, multiuser, timesharing systems were viable."
(See Douglas Comer, "Pervasive Unix: Cause for Celebration," Unix
Review, October, 1985, p. 42) Based on the results of research gained
at MIT using the Compatible Time-Sharing System (CTSS), AT&T and G.E.
agreed to work with MIT to build a "new hardware, a new operating
system, a new file system, and a new user interface." (Ibid.) Though
the project proceeded slowly and it took several additional years to
develop Multics, Doug Comer, a Professor of Computer Science at Purdue
University, explains that "fundamental issues were uncovered, new
approaches were explored and new mechanisms were invented." (Ibid) The
most important, he explains, was that "participants and observers
alike became devoted to a new form of computing (the interactive,
multiuser, timesharing system.). As a result, the Multics project
dominated computer systems research for many years, and many of its
results are still considered seminal."(Ibid.)
Evaluating the influence of the MULTICS research on Bell Labs
researchers, Comer points out that top researchers in computer science
and mathematics from the world's premier industrial research center,
Bell Labs, were able to work with top researchers from academia. When
Ken Thompson, Dennis Ritchie and their "Bell Laboratories colleagues,"
writes Comer, "later began work on their own implementation of a
Multics-like time-sharing system, they drew heavily from the Multics
experience. So, despite popular myth, UNIX was not an accidental
discovery at all -- it evolved directly from experiences with academic
research." (Ibid., p. 41-42)
By 1969, however, AT&T made a decision to withdraw from the
project. Describing that period, Dennis Ritchie, another of the
inventors of unix at Bell Labs writes, "By 1969, Bell Labs management,
and even the researchers came to believe that the promises of Multics
could be fulfilled only too late and too expensively." (from Dennis
Ritchie, "The Development of the C Language," ACM, presented at Second
History of Programming Languages conference, Cambridge, Mass, April
1993, p. 1)
Detailing the reasons for the decision, Vyssotsky responds, "It
turned out that from our point of view the Multics effort simply went
awry. In the first place, we were naive about how hard it was going to
be to create an operating system as ambitious as Multics. It was the
familiar second system syndrome. You put in everything you wished
you'd had in the other one."(Vyssotsky, pg. 59) Also he details how
GE, MIT, and AT&T each had different goals for the project, which made
it difficult for them to work together. While GE wanted to develop
Multics to "strengthen its product line," MIT wanted Multics "to
advance the state of art" of computing, and Bell Labs' purpose was to
have a good environment for our people to work in." (Ibid.) Given
these different objectives, Vyssotsky explains, "It turned out that
under the stress of slipping schedules and the increasing realization
that we had difficulty agreeing on a common course of action, we ended
up simply pulling out of Multics. We said, `OK, it's too wet to plow.
We aren't going to get from here to there'."(Ibid.)
When the decision to pull out of the Multics project was made by
AT&T, Vyssotsky explains there was an operating system that he called
a "precursor of Multics" running on their GE 645 computer. "From the
point of view of the few people who could use it," he notes, "it was a
very nice programming environment. In particular, Ken Thompson thought
it was a very nice programming environment."(Ibid.)
However, when Bell Labs pulled out of the Multics project they
took the Multics precursor off their GE 645 computer and put up GECOS,
a much less state of the art operating system. "If you were an old
line Spanish American War type computer user like me," Vyssotsky
admits, "GECOS was a perfectly satisfactory system for getting from
here to there in a well-designed application. You knew what it was
going to do." (Ibid., p. 60)
But for a research computer scientist like Ken Thompson, GECOS
was inadequate. According to Vyssotsky, "It was nowhere near as
satisfactory if you were trying to do things that were technically
difficult and imperfectly defined, which is the main task of
research."(Ibid.)
Not only for Ken Thompson's work, but for the research purposes
of the Labs, an operating system more like what Multics had promised
was needed. "I wanted a much more flexible system than BESYS or GECOS
or OS360 or anything I could see," Vyssotsky recounts, "I had various
things that I was trying to do with computers that were just plain
hard to do with existing operating systems."(Ibid.)
"Moreover, for people like Ken Thompson," Vyssotsky emphasizes,
"having this embryonic version of Multics taken away and GECOS slapped
down in its place was something of a disaster. Suddenly they were back
to square one."(Ibid.)
With the loss of the Multics experimental operating system, Ken
Thompson, Dennis Ritchie and the others at the Labs who began work on
UNIX, realized they had to focus on creating an operating system for
their programming needs. "I don't think," Vyssotsky relates, "that
either of them was particularly fascinated by operating systems until
they found themselves cast back upon GECOS. They sort of got
interested in the subject out of self defense."(Ibid.)
In his account of this period, Dennis Ritchie writes, "Even
before the GE-645 Multics machine was removed from the premises, an
informal group, led primarily by Ken Thompson, had begun investigating
alternatives." ( Ritchie, pg. 1)
Thompson and Ritchie presented Bell Labs with proposals to buy
them a computer so they could build their own interactive, time
sharing operating system. Their proposals weren't acted on.
Eventually, Ken Thompson found a little used and obsolete PDP 7
computer. According to Vyssotsky the orphaned PDP-7 computer was a
tiny machine, "more nearly in the class of a Commodore 64 than the
class of a PC-AT." (Vyssotsky, pg. 60)
Ritchie explains that Ken Thompson was attempting to create a
programming environment which included "many of the innovative aspects
of Multics," such as "an explicit notion of a process as a locus of
control, a tree-structured file system, a command interpreter as a
user-level program, simple representation of text files, and
generalized access to devices." (Ritchie, p. 1-2)
Describing the primitive conditions that Thompson faced, Ritchie
writes, "At the start, Thompson "did not even program on the PDP
itself, but instead used a set of macros for the GEMAP assembler on a
GE-635 machine. A postprocesser generated a paper tape readable by the
PDP-7. These tapes were carried from the GE machine to the PDP-7 for
testing until a primitive UNIX kernel, an editor, an assembler, a
simple shell (command interpreter), and a few utilities (like the Unix
rm, cat, cp commands) were completed. At this point, the operating
system was self- supporting; programs could be written and tested
without resort to paper tape, and development continued on the PDP-7
itself." (Ibid., pg 2)
The result, Ritchie explains, was that "Thompson's PDP-7
assembler outdid even DEC's in simplicity; it evaluated expressions
and emitted the corresponding bits. There were no libraries, no loader
or link editor: the entire source of a program was presented to the
assembler, and the output file -- with a fixed name -- that emerged
was directly executable.(Ibid., pg. 2)
The operating system was named UNIX, to distinguish it from the
complexity of MULTICS. Vyssotsky recalls that in addition to Thompson
and Ritchie, "the two most active contributors at that stage were Joe
Ossanna and Rudd Canaday. I should also add," he explains, "that Doug
McIlroy was tremendously influential on their thinking."(Vyssotsky,
pg.60) Vyssotsky elaborates, "I don't think that Doug actually
contributed much of the programming, but for example, the appearance
of pipes in UNIX was clearly a result of Doug's discussions with Ken
and Dennis." (Ibid. ) Ken put them in, but "it was McIlroy who said,
"Look you ought to do it. Pipes, like most things in UNIX were not a
radically new idea. Co-routines had, after all, shown up in SIMULA by
the end of 1967."(Ibid.)
As work continued on the Bell Labs operating system, the
researchers developed a set of principles to guide their work. Among
these principles were:
"(i) Make each program do one thing well. To do a new job,
build afresh rather than complicate old programs by adding
new features.
(ii) Expect the output of every program to become the input
to another, as yet unknown, program. Don't clutter output
with extraneous information. Avoid stringently columnar or
binary input formats. Don't insist on interactive input.
(iii) Design and build software, even operating systems, to
be tried early, ideally within weeks. Don't hesitate to
throw away the clumsy parts and rebuild them.
(iv) Use tools in preference to unskilled help to lighten a
programming task, even if you have to detour to build the
tools and expect to throw some of them out after you've
finished using them."
(from M.D. McIlroy, E.N.Pinson, and B.A. Tague
"Unix Time-Sharing System Forward",
The Bell System Technical Jounal, July -Aug 1978
vol 57, number 6 part 2, p. 1902)
By 1970, Ritchie writes, the UNIX researchers were "able to
acquire a new DEC PDP-11. The processor," he remembers, "was among the
first of its line delivered by DEC, and three months passed before its
disk arrived." (Ritchie, p. 5) Soon after the machine's arrival and
while "still waiting for the disk, Thompson," Ritchie recalls,
"recoded the Unix kernel and some basic commands in PDP assembly
language. Of the 24K bytes of memory on the machine, the earliest
PDP-11 Unix system used 12K bytes for the operating system, a tiny
space for user programs, and the remainder as a RAM disk." (Ibid., p.
5) "By 1971," Ritchie writes, "our miniature computer center was
beginning to have users. We all wanted to create interesting software
more easily. Using assembler was dreary enough that B, despite its
performance problems, had been supplemented by a small library of
useful service routines and was being used for more and more new
programs."(Ibid., p. 6)
"C came into being in the years 1969-1973," Ritchie explains, "in
parallel with the early development of the Unix operating system; the
most creative period occurred during 1972."(Ibid., p. 1) "By early
1973," the essential of modern C were complete. The language and
compiler were strong enough to permit us to rewrite the kernel for the
PDP-11 in C during the summer of that year. (Thompson had made a brief
attempt to produce a system coded in an early version of C -- before
structures -- in 1972, but gave up the effort.)" (Ibid.)
Each program they built developed some simple capability and they
called that program a tool. They wanted the programs to be fun to use
and to be helpful to programmers. Describing the achievements of the
lab, Doug McIlroy, one of the researchers and Thompson's Dept Head
when they created UNIX, describes the atmosphere at the lab:
"Constant discussions honed the system....Should tools
usually accept output file names? How to handle demountable
media? How to manipulate addresses in a higher level
language? How to minimize the information deducible from
a rejected login? Peer pressure and simple pride in
workmanship caused gobs of code to be rewritten or discarded
as better or more basic ideas emerged. Professional
rivalry and protection of turf were practically unknown:
so many good things were happening that nobody needed to
be proprietary about innovations."
[from M.D. McIlroy, "Unix on My Mind," Proc.
Virginia Computer Users Conference, vol 21,
Sept. 1991, Blacksburg, p. 1-6.]
The research done at the Labs was concerned with using the
computer to automate programming tasks. By a scientific approach to
their work and careful attention to detail, Bell Labs researchers
determined the essential elements in a design and then created a
program to do as simple a job as possible. These simple computer
automation tools would then be available to build programs to do more
complicated tasks.
They created a UNIX kernel accompanied by a toolbox of programs
that could be used by others at Bell Labs. The kernel consisted of
about 11,000 lines of code. Eventually, 10,000 lines of the code were
rewritten in C and thus could be transported to other computer
systems. "The kernel," Ken Thompson writes, "is the only UNIX code
that cannot be substituted by a user to his own liking. For this
reason, the kernel should make as few real decisions as possible."
(from K. Thompson, "UNIX Implementation", "The Bell System Technical
Journal," vol 57, No. 6, July-August 1978, p. 1931)
Thompson describes creating the kernel:
"What is or is not implemented in the kernel represents both
a great responsibility and a great power. It is a soap-box
platform on `the way things should be done.' Even so, if
`the way' is too radical, no one will follow it. Every
important decision was weighed carefully. Throughout,
simplicity has been substituted for efficiency. Complex
algorithms are used only if their complexity can be
localized."
(Ibid., p. 1931-2)
The kernel was conceived as what was essential and other features
were left to be developed as part of the tools or software that would
be available. Thompson explains:
The UNIX kernel is an I/O multiplexer more than a complete
operating system. This is as it should be. Because of this
outlook, many features are found in most other operating
systems that are missing from the UNIX kernel. For example,
the UNIX kernel does not support file access methods, file
disposition, file formats, file maximum sizes, spooling,
command language, logical records, physical records,
assignment of logical file names, logical file names, more
than one character set, an operator's console, an operator,
log-in, or log-out. Many of these things are symptoms rather
than features. Many of these things are implemented in user
software using the kernel as a tool. A good example of this
is the command language. Maintenance of such code is as easy
as maintaining user code. The idea of implementing "system"
code and general user primitives comes directly from
MULTICS."
(Ibid., p. 1945-6)
Evaluating the achievement represented by the kernel, Vyssotsky
explains, "I would say that the greatest intellectual achievement
embedded in UNIX is the success Ken Thompson and Dennis Ritchie had in
understanding how much you could leave out of an operating system
without impairing its capability."(Vyssotsky, pg. 60-62)
"To some extent," he continues, "that was forced by the fact that
they were running on small machines. It may also have been a reaction
to the complexity of Multics...It took some very clear thinking on the
part of the creators of UNIX to realize that most of that stuff didn't
have anything to do with the operating system and didn't have to be
included." (Ibid., p. 62 )
Eventually the unix operating system was adopted in other
departments at AT&T to do a variety of work. "There is one piece of
history that I think is very important to understand," explains
Vyssotsky, "When UNIX evolved within Bell Laboratories, it was not a
result of some deliberate management initiative. It spread through
channels of technical need and technical contact ... this was typical
of the way UNIX spread around Bell Laboratories. You had MTSS
Supervisors and Department Heads saying we had to go in this direction
while Executive Directors were saying, `Well, I'm awful nervous about
it. But if you guys say that is what we've got to do, I'll back your
play."(Ibid, pg. 62-64)
Explaining the importance of how unix was implemented
organizationally within the Bell System, Vyssotsky comments, "There
are a lot of organizations that do not work that way. I brought out
that little hunk of history to point out that the spread and success
of UNIX, first in the Bell organizations and then in the rest of the
world, was due to the fact that it was used, modified, and tinkered up
in a whole variety of organizations within Bell Laboratories ... the
refinement of UNIX was not done as the result of some management
initiative or council of vice presidents. It was the supervisors
saying, "This thing is already better than our other options and
flexible enough for us to make it a go." (Ibid. p. 64)
During the same period that the search for an operating system to
replace the promise of Multics had begun by Bell Labs computer
programming researchers, the Bell System was faced with the problem of
automating their telephone operations using minicomputers. Describing
the problem facing the Bell System during this period, August Mohr, in
an article in Unix Review, "The Genesis Story"(January 1985, p. 22),
writes "Bell was starting to perceive the need for minicomputer
support for its telephone operations." (Mohr was editor of /usr/group
's CommUNIXations newsletter.)
"The discovery that we had the need -- or actually, the
opportunity -- in the early '70s to use these minis to support
telephone company operations encouraged us to work with the UNIX
system," confirms Berkley Tague. ("Interview with Berkley Tague," Unix
Review, June 1985, p. 59) "We knew we could do a better job with
maintenance, traffic control, repair, and accounting applications."
(Ibid.)
"The existing systems were made up of people and paper," he
relates, "The phone business was in danger of being overwhelmed in the
early '70s with the boom of the '60s. There was a big interest then in
using computers to help manage that part of the business. We wanted to
get rid of all of those Rolodex files and help those guys who had to
pack instruments and parts back and forth just to keep things going."
During the late 1960's, AT&T was under pressure from regulatory
bodies like the New York Public Service Commission, to solve what was
termed as a "service crisis." (See especially, "Wrong Number," by Alan
Stone, N.Y., 1989, p. 145) This pressure encouraged AT&T to explore
technological advances that would make its support operations more
efficient.
Tague explains that there had been local mechanization of
processes but not large scale integration of the mechanization. "Take
repair," he suggests as an example, "A lot of it deals with keeping
the connections straight between what we call the main distribution
frames in the central office and the wires that tie residential
telephones into the switch. Prior to the use of computers,
`mechanization' consisted of somebody on a remote test bench using
electrical meters and instruments to test lines. To get those
connections made, an intercom was used to broadcast requests to a
bunch of people standing around with alligator clips and soldering
irons down in the wire center. The requests went something like,
`Would you kindly connect jumper x to terminal y?' to get testing
done."(Ibid, p. 60)
Tague describes how the mini computer made it possible to
automate this process. "First, we were able to get more instructions
out to the people actually making the connections. And, at the other
end, we were able to centralize information about entire systems and
end-to-end circuits."
"This meant," he elaborates, "that if I was responsible for
keeping the Superbowl broadcast on the air between New Orleans and New
York, I could -- with a single console -- view all the connections on
that link and have access to all of the information automatically
being collected about it. If something broke, I could immediately
recognize that and orchestrate the process of getting it repaired. The
repair itself would ultimately be left to a person working in much the
same way as before." (Ibid.)
This change affected workers like those "plugging in an alternate
module or pulling a manual switch and going to a backup system," he
clarifies. "Suddenly, their work became much faster because the
information was all in one place -- unlike earlier days when eight
guys would have had to collect and sort out the trouble data in a
series of phone calls before actually being able to get down to the
business of working on solutions." (Ibid.)
Other applications were affected as well, he explains. "in areas
like cable and wiring layouts. The algorithms applying to these
layouts were well known here at the Laboratories, but they were not
the sort of thing you could usefully put into a manual. They were,
however, easily put into computer programs. Optimum layouts could
thus be generated using the computer to assess all the complicated
engineering tradeoffs."(Ibid.)
Not only did they need a good programming environment, but Mohr
emphasized that the Bell System applications required, "Operations
Systems, not Operating Systems. With the number of systems under
consideration, the possiblity of being tied to a single vendor, or
having each site tied to a different vendor, induced a kind of
paranoia. There just had to be another way." (Mohr, p.22 )
Tague elaborates, "If we faced the phone company with 18
different vendors and 19 different environments, neither the
developers nor the phone companies were going to be able to maintain
the thing once it got out in the field in large numbers. As a
planner, I was trying to focus on a few vendors. At that time, it was
primarily Hewlett-Packard and DEC, plus a few IBM systems." (Tague,
pg. 60)
This led to the realization of a need for an operating system.
"Vendor operating systems were available as a starting point", he adds
"but a number of people had already started to build their own when
they realized that what the vendors had was not adequate." (Ibid.)
Tague explains that his role in planning for the transition meant
that he tried to warn those involved that they would need a good
software environment to do the development of the software needed to
use the mini computers for these new roles.
"I observed," he comments, "that people were starting to put
these minis out in the operating company, and saw that it was an area
of both opportunity and potential problems. I found," he adds, "that
some of the people in development had never built an operating system
for any computer before; many of them had very little software
background. They were coming out of hardware development and telephone
technology backgrounds, and yet were starting to build their own
operating systems. Having been through that phase of the business
myself, it seemed silly to go through it another hundred times, so I
started pushing the UNIX operating system into these projects." (Mohr,
pg. 22)
Tague was familiar with UNIX and its capabilities and tells the
variety of reasons ranging from inadequate file systems, to inadequate
performance, to poor user interface that he recommended the initial
adoption of UNIX to start the work. "We sold those first application
developers on UNIX simply by pointing out that the first job they were
going to have to do was program development and that by using the UNIX
operating system they could get that job done more easily. I did not
argue with them about whether or not they should develop their own
operating systems -- knowing in my heart of hearts that once they got
on UNIX they wouldn't be able to do any better with the experience and
the schedules they had. Indeed, that is what happened." (Tague, pg.
60-1)
Tague's backing of UNIX, as a development system for operations,
was not just a personal preference. "I had every confidence in the
people who built it because I'd worked with them on Multics," he
explained. "With their experience and training, I figured they could
build a much better operating system than somebody who's building one
for the first time, no matter how smart that person is." (Mohr, pg 22)
Tague describes how UNIX had been functioning in the research
environment and thus had demonstrated that it could be used as a
beginning basis for this important job.
Also, he knew that there would be a need to develop a support
system for those operating companies around the country that would
begin to use UNIX: "We were starting to put these things in the
operating companies all around the countryside," explains Tague, "and
the prospects were that there were going to be several hundred minis
over the next few years that were going to have to be maintained with
all their software and hardware." (Ibid., pg. 24)
Bell had created the needed field support system to maintain the
electronic switching machines and software that were now being
upgraded. "Supporting a network of minicomputers would be a
significantly different problem, though," August Mohr explains.
"Maintaining an operating system is not at all like maintaining an
electronic switching system. The minicomputers had different
reliablity demands, requiring a different support structure in the
organization -- one that did not yet exist in any form. In many ways,
the operations group was breaking new ground," writes Mohr. (Ibid.)
As head of the Computer Planning Department, Tague had been
responsible for systems engineering. In 1971 Tague garnered support
for UNIX to be adopted. Then he pushed to have UNIX made the internal
standard and to provide central support through his organization. By
September, 1973, he was able to form a development organization to
provide support for a "standard Unix." This group, called UNIX
Development Support worked with Bell Labs Research. Though the two
groups sometimes diverged regarding their priorities, Mohr explains
that they agreed on the need for UNIX portability.
According to Mohr, "Tague foresaw the possiblity of UNIX becoming
an inteface between hardware and software that would allow
applications to keep running while the hardware underneath was
changing." (Ibid., p. 24)
"From the support point of view," he continues, "such a
capability would solve a very important problem. Without UNIX and its
potential portability, the people building the operations support
systems were faced with selecting an outside vendor that could supply
the hardware on which to get their devlopment done. Once that was
complete, they would be locked into that vendor." However, according
to Mohr, "Portability obviated this limitation and offered a number of
other advantages. When making a hardware upgrade, even to equipment
from the same vendor, there are variations version to version. That
could cost a lot of money in software revisions unless there were some
level of portability already written into the scenario." (Ibid., pg.
24-25)
Just as Operating Systems people in the Bell system had come to
recognize the need for portability in a computer operating system,
Ritchie and Thompson and the other programming researchers at Bell
Labs had created the computer language C and rewritten the majority of
the UNIX kernel in C and thus had made the important breakthrough in
creating a computer operating system that was not machine dependent.
Describing their breakthrough with UNIX, Thompson and Ritchie
presented their first paper on UNIX at the Symposium on Operating
Systems Principles, IBM Thomas J. Watson Research Center, Yorktown
Heights, New York, October 15-17, 1973,(reference from UNIX(tm)
Time-Sharing System: Unix Programmers Manual, 7th edition, vol 2,
Murray Hill, f/n pg 20). See also Ritchie's account of the creation
of C by early 1973 in "The Development of the C Language," ACM,
presented at Second History of Programming Languages conference,
Cambridge, Mass, April 1993, p. 1) Describing this important
achievement by Bell Labs researchers, Mohr writes, "the integral
portability of the system developed by Research proved adequate to
make UNIX portable over a wide range of hardware."
With the research breakthrough of a portable computer operating
system, "the first UNIX applications were installed in 1973 on a
system involved in updating directory information and intercepting
calls to numbers that had been changed. The automatic intercept system
was delivered for use on early PDP-11s. This was essentially the first
time UNIX was used to support an actual, ongoing operating business."
(Mohr, pg. 26)
Different operations sites had taken on to create computer
software to meet similar needs, such as print spooling, mail, help,
etc. Tague's group's assignment was to gather the software and to
determine what the standard should be and send the standard back out
to the sites. Tague credits the technical strength of UNIX for making
software standardization possible. UNIX "made it easy," he explains,
"to get the right stuff in without upsetting the whole world."
Establishing a standard UNIX, according to Tague, was "a process
of negotiation and compromise with the UNIX-using community -- not a
unilateral decision." (Ibid.) His group and the people at the variety
of Bell sites "often ended up arguing things out until everybody
understood the issues and a suitable compromise was made," he relates.
(Ibid.)
Tague describes how his group the UNIX Support Group (USG) which
had been established in September of 1973 "released the first C
version of UNIX internally. [Generic I, II, and III were produced by
these intitial efforts.] In parallel with our efforts," he notes, "the
Programmer's Workbench gang under Rudd Canaday worked the same vein
over in the BIS [Business Information Systems] area.(Tague, p. 61)
The application of UNIX to automating the operating systems at
Bell also involved automating the monitoring, measurement, help for
routing and ensuring quality of calls. That was a "tall order," writes
Tony Culwick, "given the standards people have come to expect...but
the fact remains that the fundamental integrity of the national
telecommunications network depends on more than 1000 real-time,
mini-computer-based systems that are built on a version of the UNIX
operating system." (from "Reach out and Touch the Unix System," by
Tony Cuilwik, "Unix Review," June 1985, p. 50. Cuilwik was the head of
the Operations Systems Development Department at Bell Laborators and
then director of AT&T Information Systems Laboratories in Columbus,
Ohio.)
Describing the functions that UNIX makes possible, he writes,
"Among the varied and wide-ranging functions these systems perform are
network performance measurement, automated network testing, circuit
order planning, circuit order record-keeping, automated trouble
detection, automated or directed trouble repair, service quality
assurance, quality control, inventory control, customer
record-keeping, and customer billing -- as well as any number of other
operational and administrative functions. These functions all
require," Cuilwik explains, "the ability to present data to users in
real-time." (Ibid.)
The object in these systems is "to guarantee a minimal acceptable
human response time. This challenge has been met by tuning the
underlying UNIX system." (Ibid.)
Cuilwik describes how the need for such real time applications
was determined in the 1969-70 period, just when UNIX was being
created. Development, he reports, "began in earnest in 1971. Early in
this period," he writes, "it was determined that an operating system
and environment should be provided to system designers, who would then
only need to develop application-specific software." By 1974, he
reports "several sites had chosen the UNIX operating system as this
development environment. A few, meanwhile, had also selected it as an
execution environment and were busy designing enhancements and
improvements for the system." (Ibid.)
The need was also recognized for "a common operating environment
between projects." (Ibid.,p. 50-52) "Major additions" he writes,
"necessary to move the timeshared UNIX system into real-time
applications included interprocess communications (name pipes,
messages, semaphores, and shared memory), file access (logical file
system, record access system), error recovery, power fail/restart, and
line and terminal disciplines. These additions were developed,
integrated or donated to the common good by people developing specific
systems. By 1979," he reviews, "there was an enhanced real-time UNIX
system that was centrally supported, offering a collection of tools
and a number of human/machine interface designs to protect system
users from direct contact with UNIX primitives." (Ibid, p. 52)
The process of the development of UNIX so it contained such a
range of options involves its adoption and development by the academic
research community. Early in its development, word of the UNIX
operating system and its advantages spread outside of Bell Labs.
(Several sources attribute this to the paper that Ritchie and Thompson
presented on UNIX at the Symposium on Operating Principles at Purdue
in November, 1973. See for example McKusick, "A Berkeley Odyssey" in
Unix Review, January 1985, p. 31, and Peter Ivanov, "Interview with
John Lions", Unix Review, October, 1985, p. 51, about the publication
of the paper in July 1974 in the "Communications of the ACM".) The
labs made the software available to academic institutions at a very
small charge. For example, John Lions, a faculty member in the
Department of Computer Science at the University of New South Wales,
in Australia, reported that his school was able to acquire a copy of
research UNIX Edition 5 for $150 ($110 Australian) in December, 1974,
including tape and manuals. (See "An Interview with John Lions," in
Unix Review, October, 1985, p. 51)
UNIX was attractive to the academic Computer Science community
for several reasons. John Stoneback, describing these reasons, writes:
"UNIX came into many CS departments largely because it was
the only powerful interactive system that could run on the
sort of hardware (PDP-11s) that universities could afford in
the mid '70s. In addition, UNIX itself was very inexpensive.
Since source code was provided, it was a system that could
be shaped to the requirements of a particular installation.
It was written in a language considerably more attractive
than assembly, and it was small enough to be studied and
understood by individuals."
(from John Stoneback, "The Collegiate Community," Unix
Review, October 1985, p. 27.)
Describing how research UNIX helped make it possible for academic
computer science departments to establish and develop research in
computer science, he writes:
"UNIX had another appealing virtue that many may have
recognized only after the fact -- its faithfulness to the
prevailing mid-'70s philosophy of software design and
development. Not only was UNIX proof that real software
could be built the way many said it could, but it lent
credibility to a science that was struggling to establish
itself as a science. Faculty could use UNIX and teach about
it at the same time. In most respects, the system
exemplified good computer science. It provided a clean and
powerful user interface and tools that promoted and
encouraged the development of software. The fact that it
was written in C allowed actual code to be presented and
discussed, and made it possible to lift textbook examples
into the real world. Obviously, UNIX was destined to grow in
the academic community.
(Ibid., p. 27)
In trying to teach his students the essentials of a good
operating system, John Lions describes how he prepared a booklet
containing the source files for a version of Edition 6 of research
UNIX in 1976 and the following year completed a set of explanatory
notes to introduce students to the code. "Writing these," he recounts,
"was a real learning exercise for me. By slowly and methodically
surveying the whole kernel, I came to understand things that others
had overlooked."
This ability to present his students with a real example of
an operating system kernel was a breakthrough. Lions writes:
Before I wrote my notes on UNIX, most people thought of
operating systems as huge and inaccessible. Because I had
been at Burroughs, I knew that people could get to learn a
whole program if they spent some time working at it. I knew
it would be possible for one person to effectively become an
expert on the whole system. The Edition 6 UNIX code
contained less than 10,000 lines, which positioned it
nicely to become the first really accessible operating
system." (Lions, p. 52-3)
In keeping true to the UNIX community spirit of helping each
other, Lions wrote a letter to Mel Ferentz, Lou Katz and others from
Usenix and offered to make copies of his notes available to others.
After some negotiation with Western Electric over the patent
licensing, he distributed the notes titled "A Commentary on the UNIX
Operating System" to others with UNIX licenses on the conditions that
Western Electric had set out. (Ibid., p. 53)
Lions describes how he helped to develop a UNIX tool "pack" which
was eventually combined with tools created at Bell Labs called huff
and unhuff and distributed as a standard UNIX command. He and others
from his college were invited to spend periods of time at Bell Labs to
work with the unix researchers there. (See for example, pg. 57)
Describing how research UNIX and its adoption at academic
institutions has served to develop computer science, Doug Comer
writes:
The use of UNIX as a basis for operating systems research
has produced three highly desirable consequences. First, the
availability of a common system allowed researchers to
reproduce and verify each others' experiments. Such
verification is the essence of science. Second, having a
solid base of systems software made it possible for
experimenters to build on the work of others and to tackle
significant ideas without wasting time developing all the
pieces from scratch. Such a basis is prerequisite to
productive research. Third, the use of a single system as
both a research vehicle and a conventional source of
computing allowed researchers to move results from the
laboratory to the production environment quickly. Such quick
transition is mandatory of state-of-the-art computing."
(Comer, p. 44)
Not only did research UNIX serve the academic community, but the
contributions of the academic community were incorporated into
research UNIX. An example, is the work by Babaoglu and Porker at UC
Berkeley of designing a virtual memory version of UNIX for the VAX
computer which was later optimized by Bill Joy and incorporated into a
release of UNIX. (Ibid.)
Academic contributions which were incorporated into research UNIX
included the vi editor which was created by Bill Joy at University of
California at Berkeley. Describing this phenomena Comer writes:
"Many universities contributed to UNIX. At the University of
Toronto, the department acquired a 200-dt-per-inch
printer/plotter and built software that used the printer to
simulate a phototypesetter. At Yale University, students and
computer scientists modified the UNIX shell. At Purdue
University, the Electrical Engineering Department made
major improvements in performance, producing a version of
UNIX that supported a larger number of users. Purdue also
developed one of the first UNIX computer networks. At the
University of California at Berkeley, students developed a
new shell and dozens of smaller utilities. By the late
1970s, when Bell Labs released Version 7 UNIX, it was clear
that the system solved the computing problems of many
departments, and that it incorporated many of the ideas that
had arisen in universities. The end result was a
strengthened system. A tide of ideas had started a new
cycle, flowing from academia to an industrial laboratory,
back to academia, and finally moving on to a growing number
of commercial sites." (Comer, p. 43)
In the process of using UNIX within Bell Labs, bugs would be
discovered and reported to the programmers, or new applications would
be created by the departments using the programs for their own tasks.
The research labs would need to provide maintenance and updating of
software as well as getting the bug reports to the programmer and
sending out fixes.
To automate this maintenance work, Mike Lesk, one of the Bell
Labs computer researchers, proposed an automated maintenance system
that would make it possible to have the research computer call up the
computers in the departments and automatically deliver updated
software and test that it worked on the remote computer.
As part of the automated maintenance system, Lesk created a UNIX
program called UUCP (UNIX to UNIX copy) which made it possible to use
a phone or hard wired connection to have one computer poll another
computer and deliver the software.
Describing the considerations by Bell Labs at this time, Vyssotky
explains, (from Vyssotsky, pg. 64)" In 1976, there were those three
versions of UNIX. The Change Control Process on all three of those
versions was such that, at any moment in time, the people who were
programming could tell what changes had gotten in and what changes
were scheduled to go in. However, it was still a little hard for the
users to tell what they were getting. It wasn't until 1978 that we had
anything that I would consider to be a reasonable configuration
management process of UNIX. That was the point at which we finally
realized we had something which, like it or not, was a major product.
So we said, `Given that it is a major product, there can be no horsing
around.' We could no longer regard it as something in the underbrush.
We had to regularize our arrangements. We set up a process for
configuration management and we focused the thing in the direction of
a coherent system." (Vyssorsky, pg. 64-68)
But he emphasizes, "Perhaps, the most important one was that UNIX
was being used as the operating system basis for a bunch of operations
support systems in the Bell Operating Companies and we could not
afford to let those support systems go down. We put configuration
management and all of the associated paraphernalia in place about
1978. (Ibid., pg. 68)
Lions says about the freezing, "Much of the development of UNIX
in Bell Laboratories occurred before 1978. After Edition 7, many of
the original group went off to do other things. At the same time, UNIX
was becoming important within the Bell System, which gave rise to a
support group whose charter was to develop a polished and stable
version of UNIX. This group was less interested in innovation than in
stabilizing the system. Universities have simply picked up the slack.
(Lions, pg. 56)
Meanwhile, academic UNIX users had to do their own software
maintenance. Lions describes how a community of academic unix users
grew up who were willing to help each other.
"One very positive effect, however" writes Lions, "is that the
number of universities using UNIX and the lack of any formal support
forced us to band together into AUUG. (Australian unix users group
-ed) The connections we have thereby made have created and cemented
bonds between people in the different departments. UNIX has been a
very unifying influence for computer science within Australia. This
cannot be overestimated."(Ibid., pg. 57)
UUCP made such exchanges easier. It was included with the Version
7 UNIX, which was made available to the academic community outside of
Bell Labs. UUCP made it possible for UNIX users to communicate with
each other even when they were at spatially distant locations.
Using UUCP, the UNIX community was able to pioneer still another
advance, Usenet News. "Though large institutions have been able to
avail themselves of communications networks such as ARPANET, the UNIX
community has made inexpensive electronic communication available to
all of its members via Usenet," writes Stoneback, "A community that
already had so much in common," he explains, "was strengthened and
enhanced by the ability to move software easily among locations and to
maintain a reasonable electronic mail system. The cost of this network
has been borne at least in part by private industry, thus mitigating
expenses for the users themselves. The Usenet network stands today as
a clear sign that the UNIX community is solidly in place. It now
includes numerous corporate members providing universities on the
network with the added advantage of pooling academic researchers,
industrial developers, industrial researchers and regular users.
Combined with a functional, cheap electronic communication system,
Usenet offers the academic community unique advantages." (Stoneback,
p. 26)
"The network," he points out, "is the direct result of a community
that supports its members and in turn is nurtured by the ones it
serves. The community is a reasonably democratic one, reasonably open
to new ideas, resonably open to change, and reasonably generous with
its benefits."(Ibid.)
Thus by 1980, a survey conducted by the Computer Science Research
Network (CSNET) of academic institutions to find out what computer
system they used, found that "over 90 percent of all departments were
served by one or more UNIX systems." (Comer, pg. 42)
Explaining the surprising popularity that UNIX achieved despite
its grassroots distribution system, McIlroy writes, "Therein lies the
genius of Unix, which, without a sales force, and without the support
of hardware makers, was enthusiastically adopted around the world ..."
("Unix on My Mind")
"Unix," he emphasizes, "was the distilled essence of operating
systems, designed solely to be useful. Not to be marketable. Not to be
compatible. Not to be an appendage to a particular kind of hardware.
Moreover a computer running Unix was to be useful as a computer, not
just a `platform' for canned `solutions'. It was to be programmable -
cumulatively programmable. The actions of program builders were to be
no different in kind from the actions of users; anything a user could
do a program could do too...."
(Ibid.)
Describing the environment that gave birth to these advances,
McIlroy writes,
"Open systems! Our systems! How well those who were there
remember the pipe-festooned garret where Unix took form. The
excitement of creation drew people to work there amidst the
whine of the computer's cooling fans, even though almost the
same computer access could be had from one's office or from
home. Those raw quarters saw a procession of memorable
events. The advent of software pipes precipitated a day-long
orgy of one-liners...as people reveled in the power of
functional composition in the large, which is even today
unavailable to users of other systems. In another memorable
event, the unarticulated notion of software tools, which had
been bolstered by pipes, was finally brought home by the
liberation of the pattern matching program grep from within
the editor."
(Ibid.)
He continues:
"A parade of visitors came to marvel at the system and to
copy it. The makers of our 1972 model phototypesetter
goggled when they saw the paper tape input replaced by wires
straight from a computer. On-line PicturePhone[r] service
caught attention. Synthetic speech was initiated by a
memorable `Come here, Watson' event when words typed in a
remote office range out clearly in the lab: `It sounds
better over the telephone.' The computer's readings and
misreadings became a constant crowd pleaser. There was
great, if somewhat conspiratorial, excitement over a
stealthy version of the C compiler that would recognize and
silently bug the Unix login program and would propagate the
ability through future generations of the compiler
itself....No trace of the bug appeared in source code."
(Ibid.)
And UUCP and then Usenet News made this the experimental research
environment available for those not at Bell Labs, or with access to
the experimental Arpanet. "Eager to distribute his software quickly
and painlessly, Mike invented uucp, thereby begetting a whole global
network," McIlroy writes. (from "A Research UNIX Reader: Annotated
Excerpts from the Programmer's Manual, 1971-1986" by M. D. McIlroy,
Computing Science Technical Report No. 139, AT&T Bell Laboratories,
June 1987, p. 3.
Summarizing the relationship between Bell Labs and the academic
community in developing UNIX, Comer concludes:
"UNIX was not invented by hackers who were fooling
around, nor did it take shape in a vacuum. It grew from
strong academic roots and it has both nurtured and taken
nourishment from academia throughout its development. The
primary contributors to UNIX were highly educated
mathematicians and computer scientists employed by what many
people feel is the world's premier industrial research
center, Bell Laboratories. Although they were knowledgeable
and experienced in their own right, these developers
maintained professional contacts with researchers in
academia, leading to an exchange of ideas that proved
beneficial for both sides. Understanding the symbiotic
relationship between UNIX and the academic community means
understanding the background of the system's inventors and
the history of interactions between universities and Bell
Laboratories." (Comer, p. 34, 42)
Describing this fertilization, Dennis Ritchie wrote, "... Unix
enjoyed an unusually long gestation period. During much of this time
(say 1969-1979) the system was effectively under the control of its
designers and being used by them. It took time to develop all the
ideas and software, but even though the system was still being
developed people were using it, both inside Bell Labs, and outside
under license. Thus, we managed to keep the central ideas in hand,
while accumulating a base of enthusiastic, technically competent users
who contributed ideas and programs in a calm, communicative, and
noncompetitive environment. Some outside contributions were
substantial, for example, those from the University at Berkeley."
("Reflections on Software," August 1984, vol 27, No. 8, p. 75)
John Lions, reviewing his experience as part of the UNIX
community, concludes, "We have made a large number of contacts and
exchanged a great deal of information around the world through this
UNIX connection. Possibly that is the nicest thing about UNIX: it is
not so much that the system itself is friendly but that the people who
use it are. "(Lions, p. 57)
It is a rare and wonderful event in the development of human
society when a scientific and technological breakthrough is made which
will certainly affect the future course of social contributions wer
substantial, for example, those from the development and which becomes
known when its midwives are still alive to tell us about it. UNIX, the
product of researcher at Bell Labs, the then regulated AT&T system,
and academic computer science, and a valuable invention for computer
science, for computer education and for the education of the next
generation of computer scientists and engineers, is such an event.
Ronda Hauben Amateur Computerist
ro...@umcc.umich.edu or ae...@yfn.ysu.edu