Featuring recorded lectures from the Harvard School of Engineering and Applied Sciences course Computer Science 20, this course covers widely applicable mathematical tools for computer science, including topics from logic, set theory, combinatorics, number theory, probability theory, and graph theory. It includes practice in reasoning formally and proving theorems. Students meet twice a week via web conference to solve problems collaboratively. 

Meet The Author

Harry R. Lewis

Harry R. Lewis

Gordon McKay Professor of Computer Science, Harvard University

Harry Lewis is the Gordon McKay Professor of Computer Science at Harvard University, a position he has held since 1981. He received his undergraduate degree from Harvard College in 1968, and his PhD in applied mathematics from Harvard University in 1974. In between his two degrees, he served for two years as a commissioned officer of the United States Public Health Service, and spent a year in Europe as a traveling fellow of Harvard. He joined the Harvard faculty in the fall of 1974

Lewis is the author of several books and numerous articles on computer science. He served as the dean of Harvard College from 1995 to 2003, where he oversaw the undergraduate experience from residential life and academic advising to intercultural and race relations. In 2006 he published Excellence Without A Soul, a book about higher education. He served as dean of Harvard's School of Engineering and Applied Sciences in the spring of 2015.

Lewis lives in Brookline and worries constantly about the Red Sox.


  • PhD Harvard University
Deborah Abel

Deborah Abel

Software Developer, Ab Initio

AB, Harvard University

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