Fran Allen

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.

A few weeks later I got a call while I was interviewing for a faculty job at a teacher’s college in southern Illinois. I was really getting desperate—it was time to get a job and I didn’t have one. So I got that call while I was on the road and took the job, sight unseen, and got the papers to report at what turned out to be the research laboratory in Poughkeepsie.

So I went there and got started as a programmer. IBM was expanding rapidly into computing and there weren’t any computer-science courses, so they were hiring people from wherever they had found them.

Seibel: What kind of training did they give you?

Allen: Well, it was a kind of a learn-as-you-go, as I recall. There was an orientation to the company but I don’t recall there was any programming class per se, which is odd in retrospect. I suppose there were some classes, depending on what your background was. It was all very informal.

The first assignment I got, because I’d been a math teacher, was to teach the scientists and other programmers Fortran. I had joined in July of 1957 and Fortran had been issued as a product on April 15 that same year. And IBM Research—the group I was in—had an edict that by September all the programming had to be done in Fortran. That was the way to convince their own people, just as they were trying to get outside people to, to use it.

Seibel: So these were scientists within IBM, doing their own scientific computation?

Allen: Yes. The machine they had was the 704 machine and that’s what Fortran was originally designed for and optimized to. They were used to writing in assembly code right on the machine, doing the same thing I had done at the University of Michigan, running their own programs—scheduling some time and running the programs. They did not believe that it would be possible for any high-level language to do nearly as well as what they could do programming the machine itself.

Seibel: And that was the last time scientists adopted a new language, because they’re still using Fortran, right?

Allen: That’s right. Well, it was an unhappy class. But in the end, it was an amazing experience for all of us because Fortran was not only a language, but they had provided a compiler which was extremely advanced, and laid the foundations for the structure of compilers today.

Seibel: The next big project that you worked on, that I know about, was the Stretch computer. Did you work on anything in between this time and the Stretch project?

Allen: There were two projects that I was involved with between Fortran and the Stretch compiler. One of them was the Monitored Automatic Debugging system, which was down at the assembly level for the 704. I really enjoyed that.

It was a very early operating system. There were three of us who worked on it. We installed some buttons on the computer, because you could do that, at that time and one was a panic button. When the program appeared to loop one could just push the panic button. Then we wrote the debugger, and one of my tasks was to take the assembly-language program and produce the column binary—rotate the output of it. When you used a card reader the data was row-binary, which means each row contained the bits that were associated with the instruction, but on tape things were read differently, so it needed to be column-binary. I still have the program.

One of the things I remember really enjoying is reading the original program—and considering it very elegant. That captured me because it was quite a sophisticated program written by somebody who had been in the field a while—Roy Nutt. It was beautifully done.

Seibel: What makes a program beautiful?

Allen: That it is a simple straightforward solution to a problem; that has some intrinsic structure and obviousness about it that isn’t obvious from the problem itself. I picked up probably a habit from that of learning about programming and learning about a new language by taking an existing program and studying it.