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Barbara Liskov Gives Computer Science and Life Lessons

Watch a video of the lecture here.

In spring 1968, Barbara Liskov became one of the first women in the United States to receive a PhD in computer science.

Forty-three years later, she received an honorary doctorate at Northwestern’s 153rd commencement on June 17 for providing the basis for virtually every software program underpinning today’s society.

How did she become so successful? By following one interesting computing problem to another, collaborating with other great minds, and creating a work/life balance, she said during her McCormick Dean’s Seminar Series talk on June 16. Speaking to a packed room of faculty and students, Liskov offered a glimpse into her journey as a computer science pioneer.

The journey began when, after receiving her PhD, she began working for the Mitre Corporation, where she designed both a new computer architecture that used microprogramming.

It was a victory for Liskov, but it begged one question: “Is this actually good for anything?” To answer that, Liskov created a new sort of operating system – ”It was a hot research topic then,” she said – that managed software complexity and supported five or six concurrent users on a small computer.

But after her successes in industry, Liskov made what would turn out to be a key career move: She became a professor at MIT.

“You have the freedom to work on whatever you want to work on,” she said. And that freedom suited her well: She went on to design and implement programming languages like CLU and Argus, and she developed a definition of subtyping that became known as the Liskov Substitution Principle.  She became a member of the National Academy of Engineering and a fellow of the American Academy of Arts and Sciences, and she received the 2008 Turing Award from the ACM – one of the highest honors in the computer science field.

During her talk she offered a list of key papers that influenced her and the early development of computer science (including, “Goto Statement Considered Harmful, a letter by professor Edsger Dijkstra in the March 1968 Communications of the ACM, which advocated structured programming) and urged students to look back and consider the history and development of the computer science field.

She also offered a few life lessons. Early on, she learned to work hard during the day, then come home at a decent hour and leave her work at work. That allowed her to have a family and gave her mind the break it needed.

“The downtime was really useful,” she said. By letting her subconscious take over during the night, a solution would often come to her during the drive into work the next day.

When she began working with graduate student Steve Zilles in 1973, they would meet for daily lunches looking out on a courtyard, discuss what they had found, then return to their work that afternoon. That allowed them to work and think separately before seeing how their findings fit together.

“It was a very effective method of doing research,” she said.

The ultimate professional validation of her work came when she won the Turing Award in 2008 for her work in the design of programming languages and software methodology that led to the development of object-oriented programming. After the award was announced, her husband came across a comment on a website that asked why Liskov was getting an award for something everyone already knew. Her discoveries had become so ingrained in the field that they now seemed as though they had always been there.

Liskov continues to do research; she leads the program methodology group in the Computer Science and Artificial Intelligence Laboratory at MIT and continues to do work in data abstraction.

“There is a ton of work to be done,” she said. “Computer science is a great field.”