Seibel Peter. Coders at Work
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L Peter Deutsch
445
achievement was that he and a guy at SRI named Bob Boyer built a really
kick-ass theorem prover. And he built up a whole group around this piece
of software and built up these big libraries of theorems and lemmas about
particular domain areas.
So they had this thriving little group doing theorem proving, which was the
subject of my PhD thesis and which had always interested me. And they had
this amazing result on the arithmetic unit of the AMD CPU. So I thought,
“Hey, this is a group that has a lot of right characteristics: they’re doing
something that I’ve always been interested in; they’re run by a guy that I
know and like; their technology is Lisp-based. It’ll be really congenial to me.”
So, I went down there and gave a talk about how, if at all, could theorem
proving have helped improve the reliability of Ghostscript? By that time, we
had a big history in the bug tracker for Ghostscript. So I picked 20 bugs,
more or less at random, and I looked at each one and I said, “OK, for
theorem-proving technology to have been helpful in finding or preventing
this problem, what would have had to happen? What else would have had
to be in place?”
The conclusion I came to is that theorem-proving technology probably
wouldn’t have helped a whole lot because in the few places where it could
have, formalizing what it was that the software was supposed to do
would’ve been a Herculean job.
That’s the reason why theorem-proving technology basically has—in my
opinion—failed as a practical technology for improving software reliability.
It’s just too damn hard to formalize the properties that you want to
establish.
So I gave this talk and it was pretty well received. I talked with a couple of
the graduate students, talked with J. a little bit, and then I went away. I
thought to myself, “The checklist items all look pretty good. But I’m just not
excited about this.”
I was kind of flailing around. I’ve sung in a chorus for years. In the summer
of 2003 we were on a tour where we actually sang six concerts in old
churches in Italy. My partner was with me on that trip and we decided to
stay in Europe for two or three weeks afterwards.
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L Peter Deutsch
446
We went to Vienna and did the things you do in Vienna. The old Hapsburg
Palace has now been divided—part of it—into ten different little specialized
museums. I saw in the guidebook that there was a Museum of Old Musical
Instruments.
I went to this museum, and it’s in this long hall of high-ceilinged old salons.
And it starts with, I don’t know whether they’re Neolithic, but very old
musical instruments, and it progresses through. Of course, most of their
musical instruments are from the last couple of centuries in Western
Europe. I didn’t actually make it all the way through; I was like one or two
salons from the end and I was standing there and here was a piano that had
belonged to Leopold Mozart. And the piano that Brahms used for practicing.
And the piano that Haydn had in his house.
And I had this little epiphany that the reason that I was having trouble
finding another software project to get excited about was not that I was
having trouble finding a project. It was that I wasn’t excited about software
anymore. As crazy as it may seem now, a lot of my motivation for going into
software in the first place was that I thought you could actually make the
world a better place by doing it. I don’t believe that anymore. Not really.
Not in the same way.
This little lightning flash happened and all of a sudden I had the feeling that
the way—well, not the way to change the world for the better, but the way
to contribute something to the world that might last more than a few years
was to do music. That was the moment when I decided that I was going to
take a deep breath and walk away from what I’d been doing for 50 years.
Seibel: But you do still program.
Deutsch: I can’t help myself—I can’t keep myself from wanting to do things
in ways that I think are fun and interesting. I’ve done a bunch of little
software projects of one sort or another over time, but only two that I’ve
paid ongoing attention to over the last several years.
One has been spam-filtering technology for my mail server. I wouldn’t say it
was fun but it had a certain amount of interest to it. Based on the logs that I
look at every now and then, the filter is actually picking up—depending on
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L Peter Deutsch
447
who’s ahead in the arms race at any given moment—somewhere between
80 and 95 percent of the incoming spam.
The other substantial piece of software that I keep coming back to is a
musical-score editor. And the reason that I do that is that I have done a fair
amount of investigation of what’s available out there. I used Finale at a
friend’s house a few times. It sucks. The quality of that system is so bad I
can’t even tell you. I got a copy of Sibelius. I actually got a Mac laptop
primarily so that I could run Sibelius. And discovered that the way that they
did the user interface, it is the next thing to unusable if you don’t have a
Num Lock key. Mac laptops do not have a Num Lock key. And there were
some other things about the user interface that I didn’t like. So, I decided to
roll my own.
I’ve been through four different architectures and I finally got one that I like
pretty well. But it’s been kind of an interesting learning experience. That’s
an interactive application that’s large and complex enough that these system
issues do come up, these issues of interfaces.
After having gone through four different architectures I wound up with an
architecture for the rendering side of the program—which I think is by far
the hardest part—based on equational programming. You define variable
values in terms of equations then you let the implementation decide when
to evaluate them.Turns out that’s not too hard to do in Python. It’s been
done at least two other times that I know of. I like the way I do it because it
has the least boilerplate.
So yeah, so I still do a moderate amount of programming and I still have fun
with it. But it’s not for anybody and if I don’t do programming for weeks at a
time, that’s OK. When that was what I did professionally, I always wanted
to be in the middle of a project. Now, what I want to always be in the
middle of is at least one or two compositions.
Seibel: You said before that you thought you could make the world a
better place with software. How did you think that was going to happen?
Deutsch: Part of it had nothing to do with software per se; it’s just that
seeing anything around me that’s being done badly has always offended me
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L Peter Deutsch
448
mightily, so I thought I could do better. That’s the way kids think. It all
seems rather dreamlike now.
Certainly at the time that I started programming, and even up into the
1980s, computer technology was really associated with the corporate
world. And my personal politics were quite anticorporate. The kind of
computing that I’ve always worked on has been what today we would call
personal computing, interactive computing. I think part of my motivation
was the thought that if you could get computer power into the hands of a
lot of people, that it might provide some counterweight to corporate
power.
I never in my wildest dreams would have predicted the evolution of the
Internet. And I never would’ve predicted the degree to which corporate
influence over the Internet has changed its character over time. I would’ve
thought that the Internet was inherently uncontrollable, and I no longer
think that. China shows that you can do it pretty effectively.
And I think there’s a good chance that if Microsoft plays its cards right, they
will have a lock on the Internet. I’m sure they would love to, but I think they
might be smart enough to see the path from where they are to having what
effectively is control of essentially all the software that gets used on the
Internet.
So I’m not really much of an optimist about the future of computing. To be
perfectly honest, that’s one of the reasons why it wasn’t hard for me to get
out. I mean, I saw a world that was completely dominated by an unethical
monopolist, and I didn’t see much of a place for me in it.
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C H A P T E R
12
Ken Thompson
Ken Thompson is the original bearded Unix hacker. He has spent a career
working on whatever he finds interesting, which has, at various times, included
analog computing, systems programming, regular expressions, and computer
chess.
Hired as a researcher at Bell Labs to work on the MULTICS project, after Bell
Labs pulled out of MULTICS, Thompson went on, with Dennis Ritchie, to invent
Unix, an endeavor for which he fully expected to be fired. He also invented the B
programming language, the precursor to Dennis Ritchie’s C.
Later he got interested in computer chess, building Belle, the first special-purpose
chess computer and the strongest computerized chess player of its time. He also
helped expand chess endgame tablebases to cover all four- and five-piece
endgames.
When working on Bell Lab’s Plan 9 operating system, he devised the now
ubiquitous UTF-8 Unicode encoding.
In 1983, Thompson and Ritchie received the Turing Award for their “development
of generic operating systems theory and specifically for the implementation of the
Unix operating system.” He was also awarded the National Medal of Technology
and the Institute of Electrical and Electronics Engineers Tsutomu Kanai Award,
both for his work on Unix.
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In this interview he talked about his early love of electronics, a rather unorthodox
academic career that had him teaching courses while he was still a student, and
why modern programming scares him.
Seibel: How did you learn to program?
Thompson: I was always fascinated with logic and even in grade school I’d
work on arithmetic problems in binary, stuff like that. Just because I was
fascinated.
Seibel: Did you turn them in that way?
Thompson: No, no. But I worked out the algorithms for adding in
different bases, what carry means, and what each column means and things
like that. Then I had a little calculator, a decimal calculator. It was like a
decimal abacus. Instead of one and two it had a slide from zero to nine. It
had a subtract one from a previous column down and an add one from the
previous column up. So you’d put a stylus in, like a four, and run it up and
hook over if you want to carry. And I built some binary stuff based on that
and how that generalized to n-ary.
Seibel: Where did you even get that notion of binary arithmetic?
Thompson: In the class at the time I actually started doing this, they
introduced binary.
Seibel: Were you a victim of the “new math?”
Thompson: No, no. I was victim of bad math. I moved every year or so
and I was in some really, really horrible schools and then some good
schools. So I would have to do two years of work in one year and then I’d
be off a year. I was just loafing through math, so I had a horrible math
primary education. And this one class they just described binary arithmetic. I
took that and extended it to any base and played with that. So that’s kind of
where I got started.
Seibel: And that was in grade school?
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Ken Thompson
451
Thompson: Yeah, seventh grade. Then around senior year in high school,
somewhere around in that time, I was into electronics a lot, building radios
and amplifiers and oscillators and theremins. And I got hooked on analog
computing. It was really marvelous. Electronics was my passion during all
that time. I went into double E at Berkeley, and there I saw real digital
computers for the first time in my junior year.
Seibel: And so what year would that have been?
Thompson: I went to junior semester early, so it was three semesters in. I
started school in September ’60, so it would be the fall or spring of ’62.
They had an analog computer which I had a great time with. And they had a
G15, a drum computer. They had one lab class on it and then it was open.
Anybody could play with it, but no one did, so it was free. And I used it
essentially exclusively. I wrote programs on it, on my own, to scale an
analog computer—analog computing is almost all scaling.
Seibel: Scaling in the sense of?
Thompson: Time scaling and amplitude scaling. Basically what you do is
you build it to do a function. You put some input in and then you get a
function of that input out and you concatenate these things with feedback.
And at every point in this process you can’t go too high or you’ll clip.
Likewise there’s time scaling—you halve the frequency at different places or
double the frequency in different places. And when you do that, a bunch of
the linear scaling changes also. So if you have a simple job that doesn’t need
scaling, analog is really great. But as soon as you need scaling it becomes
very, very complex. And so I wrote digital computer programs to scale the
analog computer setups. Without computing the actual wave forms, you
compute the amplitude and frequency of the wave form at every point. And
then it tells you when you’re out of range for whatever operation you’re
doing at that time.
Seibel: And the programs on the digital computer were written in assembly
or Fortran?
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Ken Thompson
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Thompson: They were assembly mostly. There was an interpreted
language that turned out to be too slow. That’s why I was forced to go to
assembly and actually learn what the computer was.
Seibel: So load in your program, hit the run button, and away you go. Was
it using punch cards?
Thompson: No, no. It was a Flexowriter, which is like a Teletype and
paper tape. And you’d store it on paper tape and talk to it on the
Flexowriter.
Seibel: Did they actually teach you assembly in that lab?
Thompson: Nah.
Seibel: What was your next exposure to programming?
Thompson: This G15 had an interpreter called Intercom 501. And the
double-E class would program it in Intercom. There was a graduate student
that I was friends with that wrote an interpreter for Intercom on the big
IBM machine, the big campuswide computing facility. I got a listing of that
and on vacation, Christmas or something, I read it and just dissected it. I
didn’t know the language it was written in. which happened to be NELIAC.
And it was just a marvelously written program. And I learned programming,
NELIAC, Intercom, and how to interpret something—everything—from
that. I just sat and I read it for probably the entire vacation, a week. And
then came back and asked him questions about it, nagging little bugs kinds of
things. After that I knew how to program and I was pretty good at it. Then I
got jobs programming.
I was basically working my way through school, work-study and then odd
jobs. I was a research assistant—a grunt for a graduate student to get
programming done for his thesis. And I was a TA. I did programming for the
computer center. Part of the computer-center stuff was to sit in a little
booth and have people come in and say, “I only changed one thing.” “Well,
let’s look at that one thing and see what happened to you.”
Seibel: Did that hone your debugging skills or was it all just incredibly
stupid stuff?
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Ken Thompson
453
Thompson: It honed that type of debugging—you understood common
errors really well after that. Somebody who had spent days working on
their program would come in and you’d say, “Right there!”
Seibel: And your degree was in double E? Did they offer a computer-
science degree at that point?
Thompson: No, all over the United States at the time computer science
was trying to come out, and it was coming out in two ways. It was coming
out theoretically through math, or practically through double E. In Berkeley,
computer science at that point was almost exclusively inside of electrical
engineering. Math was trying, but they just weren’t politically astute enough
to compete with these old grizzled guys.
Seibel: Berkeley obviously ended up being known for things like the
Berkeley Systems Lab—building things—as opposed to being renowned for
contributions to theory.
Thompson: Yes, absolutely. This is the genesis of either a theoretical
computer-science department, like Cornell, or the Berkeley kind of
computer science. It really gives the flavor to the place. So I spent one year
in graduate school there, not because I had any ambitions for anything. It’s
just because I had nothing else to do and I was having a good time.
Seibel: Immediately after college?
Thompson: Yeah. To be honest, I was working at the university and I
didn’t even apply for graduate school. One of the professors essentially
applied for me and told me I was in graduate school.
Seibel: Still in double E?
Thompson: Right. My senior year and my graduate year were just
immense fun. I didn’t do anything that I didn’t want to do. There were no
requirements, no nothing. To graduate I took a summer course in American
history or something, some requirement, to get a degree. But outside of
that, my senior year and my graduate year I taught about half of the courses
I took.
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The basic theory of computing was just coming out then. Shell sort came
out and no one could figure out why it was faster than n-squared sort. And
so everyone was doing tests on it and trying to figure out—it’s pretty easy
to see it sorts, but nobody knows why it’s fast. And they were taking the
asymptote and figuring out why it was n to the 1.3 or something like that.
And that’s just not a natural number. And from that—shell sort and the
intellectual attraction to shell sort and why it was fast—came all this speed
order of computing. And the first n log ns and divide and conquer and all
that struck. It was an amazing, exciting era.
I had friends, a bunch of these very junior professors—a math professor I
was real close to, and a double-E professor I was close to, and the graduate
student that I worked for, and others. They would invent a class for me, and
then I would teach the class.
Seibel: Were you officially taking the class or were you actually on the
books as teaching it?
Thompson: No, no, I wasn’t on the books as teaching it. They were all
double-E 199, which meant individual research or group research or
something. And they would invent a class and give it a title and then turn it
over to me. And there’d be three or four students there.
Seibel: Of which, officially, you were one.
Thompson: Yes.
Seibel: Did you like teaching?
Thompson: To an extent. I’ve gone back and taught twice. Taken a year
off and taught one year at Berkeley in ’75–‘76 and one year in Sydney in ’88.
It’s fun. I really, really enjoy it. I was doing research in the labs and I went to
Berkeley to teach and to learn the classes I was teaching from the bottom
up since I never had a computer-science education. A normal visiting
teacher teaches one class. I taught five classes. Some classes I taught twice
and I thought they were the best because the first year I was learning and
the second time I taught it I knew where it was going and I could present it
organized and be two steps ahead of the students. The third class was just
boring. I taught one class three times and it was just wrong. So I could never
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