Peter Seibel - Coders at Work - Reflections on the craft of programming

Seibel:You’ve mostly worked in research and it seems you’ve had a lot of latitude to work on what you like, but did it change when it become a job? Did it take any of the fun out of it?

Thompson:No. It’s always been fun, and mostly because I just selected what I wanted to do. And even when it was a job, back in college, there were tons and tons of jobs available. It seemed to me that there were tons of people who were doing something, whatever it is, and they needed some little programming task done on the side to aid them. So they were perfect for me. They were little tiny jobs that I could get into, get in and out in days and pick and choose which one I wanted to take.

I think my first one was a humanities professor cataloging Homer’s work. And he had The Iliad and The Odyssey on cards. He wanted word frequencies and counts—essentially statistical analysis of these two works. And that was fun. It was text processing, which just wasn’t done by computers in those days. So that was my first odd job.

Seibel:In a 1999 interview you talked about how you had told your son he should go into biology instead of computers because you thought computers were played out. That was almost ten years ago. How do you feel about that now?

Thompson:I feel the same. Nothing much new has happened in computers that you couldn’t have predicted. The last significant thing, I think, was the Internet, and that was certainly in place in ’99. Everything has expanded—the speed of individual computers is still expanding exponentially, but what’s different?

Seibel:Reading the history of Unix, it seems like you guys basically invented an operating system because you wanted a way to play with this computer. So in order to do what today might be a very basic thing, such as write a game or something on a computer, well, you had to write a whole operating system. You needed to write compilers and build a lot of infrastructure to be able to do anything. I’m sure all of that was fun for its own sake. But I wonder if maybe the complexity of modern programming that we talked about before, with all these layers that fit together, is that just the modern equivalent of, “Well, first step is you have to build your own operating system”? At least you don’t have to do that anymore.

Thompson:But it’s worse than that. The operating system is not only given; it’s mandatory. If you interview somebody coming out of computer science right now, they don’t understand the underlying computing at all. It’s really, really scary how abstract they are from what a computer is or even the theory of computing. They just don’t understand it.

Seibel:I was thinking about your advice to your son to go into biology instead of computing. Isn’t there something about programming—the intellectual fun of defining a process that can be enacted for you by these magical machines—that’s the same whether you’re operating very close to the hardware at a very abstract level?

Thompson:It’s addictive. But you wouldn’t want to tell your kid to go into crack. And I think it’s changed. It might just be my aging, but it seems like when you’re just building another layer on top of another layer on top of another layer, you don’t really get the benefit of writing, say, a DFA. I think by necessity algorithms—new algorithms are just getting more complex over time. A new algorithm to do something is based on 50 other little algorithms. Back when I was a kid you were doing these little algorithms and they were fun. You could understand them without it being an accounting job where you divide it up into cases and this case is solved by this algorithm that you read about but you don’t really know and on and on. So it’s different. I really believe it’s different and most of it is because the whole thing is layered over time and we’re dealing with layers. It might be that I’m too much of a curmudgeon to understand layers.

Planning to be a math teacher but needing to pay off her student loans, in 1957 Fran Allen took what she intended to be a temporary job as a programmer at IBM Research. Her first assignment: teach resistive IBM scientists the newly invented language Fortran.

Instead of returning to teaching, Allen stayed at IBM for 45 years and worked on a series of compiler projects, including the compilers for the STRETCH-HARVEST machine and the ambitious but never-built ACS-1 supercomputer as well as her own PTRAN project, which developed techniques for automatic parallelization of Fortran programs and developed the Static Single Assignment intermediate representation, which is now widely used in both static and just-in-time compilers.

In 2002 Allen was awarded the Turing Award for her “pioneering contributions to the theory and practice of optimizing compiler techniques,” becoming the first female recipient in the 40-year history of the prize. She was also the first woman to be named an IBM Fellow, IBM’s top technical honor. She is also a fellow of the IEEE and the Association for Computing Machinery and a member of the National Academy of Engineering, the American Academy of Arts and Sciences, and the American Philosophical Society.

Over her career, Allen has observed the changing role of women in computing, from her earliest days when women were specifically recruited by companies like IBM for the new and ill-defined job of “programmer,” to later decades when the field became largely male-dominated.

In our conversation she talks about what that transition was like as well as why it is important to increase the diversity in the field and how C has grievously wounded the study of computer science.

Seibel:How did you get involved in programming? I know you started out planning to be a math teacher but took a job at IBM in order to pay your student loans.

Allen:To be a fully certified teacher in New York state required a master’s degree. I had an undergraduate degree in mathematics, a minor in physics, and had taught for two years. Then I went to the University of Michigan and focused very much on mathematics. At the University of Michigan, in order to get a master’s degree, one had to take two courses outside one’s field, so I took a course on computing. Computer science didn’t exist then, in 1957. It was ten years later that it started to emerge seriously. But they had a couple of courses in the engineering school.

Seibel:What did they teach you?

Allen:They had an IBM 650 machine, which was quite a different machine than what we’re used to today, and the students learned to program that machine. That involved not only learning all about the machine itself and coding in, essentially, assembly language but also running your programs on the machine. It was a really hands-on experience.

Seibel:So you would punch your deck, take it to the machine yourself, and feed it through yourself?

Allen:Right. And then go and fix it. It was a drum machine—the drum was constantly spinning and that’s where your instructions were. So the way one got it to run fast involved spacing the placement of the instructions on the drum so as it turned the next instruction would be in the right place.

Seibel:Then the IBM recruiters came around. What was it about working at IBM that appealed to you?

Allen:Well, I just needed a job. I had this debt and the recruiter came on campus and it was in the right geographical area, back in New York state. So I filled out an application and really didn’t realize much about what group I was interviewing with, the fact that it was IBM Research. I was kind of clueless about that.