Who Invented Modern Programming Languages?

Today, it can be difficult for many of us to imagine what our lives would be like without computers. One the many innovators we can thank for contributing to modern programming languages that have made computer programs more reliable, more secure and easier for us to use is National Inventors Hall of Fame^® Inductee Barbara Liskov.

A Pioneering Path

Born in Los Angeles in 1939, Liskov grew up in San Francisco. From a young age, she was interested in mathematics and science, and she decided to major in math and minor in physics when she enrolled at the University of California, Berkeley. One of only a few women in the math program at the time, Liskov earned her bachelor’s degree in 1961.

Following her graduation, Liskov joined Mitre Corp., where she was introduced to the growing field of computer programming. “I discovered the work was very interesting and I was good at it,” she recalled.

After spending a year at Mitre, Liskov took on work at Harvard University, where she maintained a program used in a language translation research project. In 1963, she enrolled at Stanford University and joined the university’s graduate program in computer science. There, she worked with professor John McCarthy on applying artificial intelligence (AI) for a program to play chess. “My thesis was finding heuristics as a way to tackle the problem of end games,” Liskov explained in an interview with the National Inventors Hall of Fame. “And McCarthy was one of the early giants in the field.”

Liskov graduated from Stanford in 1968, becoming one of the first American women to earn a doctorate in the field. When she did not receive good offers for faculty positions, she returned to Mitre and accepted a research position in computer design and operating systems – a role that involved doing research for the government.

At Mitre, Liskov created the “Venus Computer,” using a technique called microprograming, to support the construction of complex software. This led to the development of the Venus operating system, a multiprogramming system allowing several people to use the same small computer at the same time.

Following her work on the Venus system, around 1970, Liskov was tasked with looking into the software crisis. This was a series of software challenges related to writing useful, efficient programs during the early days of computer science. “This got me into the field of program methodology, which is where people were looking for solutions,” Liskov said. “That was my last project at Mitre, and in the middle of this project, I was invited to apply to [the Massachusetts Institute of Technology].”

In 1972, Liskov joined MIT as a professor and researcher. At the time, there were nearly 1,000 faculty members. ”Only 10 were women,” Liskov said. “I was the first woman in computer science and the second in my department.”

A Lasting Impact

Liskov was determined to develop more reliable computer systems. In her efforts to achieve this, she created an approach called data abstraction. Basically, data abstraction provides access while hiding details that could make access more challenging. With this approach, she showed how software could be made easier to construct, modify and maintain by focusing on data rather than process.

Laying the foundation for future programming languages, Liskov led the design and application of CLU (short for “cluster”). CLU is an object-oriented programming language that uses data abstraction to organize code into modules.

Expanding on the principles of CLU, Liskov also led the development of the Argus language, which allowed developers to write programs containing components running on different computers and made it easier to manage complex, distributed systems.

Liskov approached each programming challenge as a mathematical problem, applying principles of logic. “One advantage to being in the field so early was that great problems were sitting there,” Liskov said. “All you had to do was jump on them.”

Today, every major programming language, including Ada, Java, C++ and C#, is built on the foundation of CLU. These languages are widely used for computers, smartphones, the internet, and a wide range of financial, medical, consumer and business applications.

Since her retirement, Liskov has continued to research and innovate through work focusing on programming languages, program methodology, distributed computing and developing reliable storage systems.

Liskov’s many honors include a lifetime achievement award from the Society of Women Engineers, the A.M. Turing Award from the Association of Computing Machinery and the IEEE Computer Society's Computer Pioneer Award.

Reflecting on her work, Liskov said, “I was paying attention to what I was good at and what I enjoyed. Both properties are important if you’re going to have a happy and successful career.”

See Her Story

To watch Liskov tell her story in her own words, watch this new video created by the National Inventors Hall of Fame in partnership with the United States Patent and Trademark Office. It offers an inspiring look into her life and work.

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