My Career in Computer Science

By Barbara Liskov

Barbara Liskov

Barbara Liskov

When I was young, it was uncommon for women to have careers. After World War 2, there was pressure on women to stay at home. I have often wondered what led me to go in a different direction.

My parents expected me to go to college and to excel academically, but not to have a career. My father was concerned that I be able to support myself — if I had no husband to support me. What I would do in this case was never spelled out, but my impression was that I could be a teacher or a secretary. My father was a lawyer, but my having such a profession did not appear to be a possibilitity.

On the other hand, I was never told that certain things shouldn’t be done by women. It was O.K. for me to be interested in math and science. I think this “O.K.” enabled me to follow this interest in spite of the discouragement I sensed in high school. I just kept a low profile but took the courses that interested me.

This approach continued when I went to college at UC Berkeley. I started out in physics but quckly switched to math because I liked it better. I especially liked discrete math, the kind of math most closely related to computer science, but I knew nothing of computers at this point.

When I graduated from college, I applied to grad schools, and one funny incident occurred. I naively applied to Princeton since I knew it was highly rated in math. I got back a letter saying that they didn’t accept women (this was 1961). Although I was accepted elsewhere, I decided to get a job instead. I looked for one in math, but all I could find was boring work such as drawing graphs. However I was able to find an interesting job as a programmer. And that is how I got into computer science.

I worked at the Mitre Corporation for a year and then switched to Harvard, where I maintained a program to parse English sentences. Then I decided to return to graduate school because I wanted to learn at a faster pace than was possible in my job. So I enrolled at Stanford in the fall of 1963.

When I got to Stanford, computer science was still in its infancy. There wasn’t a department until 1965 and I was in the first group of students to take the qualifying exams. I did research in AI, working with John McCarthy, and my thesis was on a program to play chess endgames.

I received my PhD in 1968, but wasn’t able to find a good job as a professor. So I ended up back at Mitre, this time as a researcher. I wanted to move to the Boston area because the man who later became my husband lived there.

I stayed at Mitre for 4 years and working there turned out to be very good for me. I knew part way through grad school that I wanted to move from AI to systems. At Mitre I did research in computer architecture, operating systems, and programming methodology. Working a Mitre gave me the opportunity to focus on switching areas without having the pressures of being a faculty member. I think the switch would have been much more difficult otherwise.

I moved to MIT in 1972. By this point Title 9 had passed and universities were becoming interested in hiring women faculty. This was definitely true at MIT, under the guidance of its president, Jerry Weisner. My department (Electrical Engineering and Computer Science) was also looking actively under the leadership of Louis Smullin and Bob Fano. I was recruited based on my research at Mitre on the Venus operating system, which led to a prize paper at SOSP.

When I joined MIT I believe there were only 10 women faculty (out of 1000). I was the first woman faculty member in computer science, and the second in my department; the first was Millie Dresselhaus — a very distinguished person! Women faculty members were so rare that at the reception for new faculty, one of the senior people there introduced himself to my husband, whom he wanted to welcome to MIT. As an aside, I thought this was funny and I have found a sense of humor very useful over the years.

The switch to MIT came at a very good time for me because I had started to work on programming methodology at Mitre and by the time I got to MIT I knew the research direction I wanted to follow. MIT gave me the freedom to define my own research agenda and it gave me access to the wonderful students who have been so important to my success.

During the first year at MIT I invented the notion of data abstraction, and I subsequently worked with Steve Zilles, who had similar ideas, to develop the first definition of an abstract data type. In the second year I started to work on the CLU programming language. When CLU was finished in the late 70s, I moved into distributed systems. At that point the Arpa net existed and was being used for email, file transfer, and remote login. There was a dream that it would be possible to have distributed programs that ran on many computers connected by a network, but no one knew how to do this. I thought it looked like a very interesting research problem and so I moved research areas again.

Most of my work since then has been in distributed systems. However I continued to work in programming methodology for many years. I developed a course at MIT with the goal of teaching students how to develop big programs. Also in the mid-80s I invented what has come to be called the Liskov Substitution Principal, which is one of the key concepts that underlies object-oriented programming.

On a personal side, I married in 1970, and had a child (my son, Moses Liskov) in 1975 — when I was an untenured faculty member. I found it challenging but manageable to combine being a faculty member with raising a family. An important reason was that my husband was very supportive.

In addition to research I have tried to pay back, especially to MIT. In 2001 I became the head for computer science and worked in this position for 3 years. One important accomplishment was that I hired 5 outstanding women, bringing the number of women faculty in computer science from 4 to 9. (I hired a number of outstanding male faculty as well!) At the present time I serve MIT as Associate Provost for Faculty Equity. My charter is to help MIT as a whole increase diversity without affecting quality.

When I look back over my career, I am struck by how much fun I have had, and how creative the work is. I am always amused to discover that people think engineering isn’t fun and creative. How wrong they are! I hope that all of you Systers have as much fun in your careers as I have had in mine.

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