Clarence Ellis

Quick Facts

Born: 11th May 1943

Died: 17th May 2014

Nationality: American

Occupation: Computer Scientist and Emeritus Professor of Computer Science and Cognitive Science at the University of Colorado at Boulder

Known for: Being the first African American to obtain a PhD in computer science.

Childhood and Education

Clarence Ellis was born in Chicago, Illinois in a poor family. He wasn’t very popular at school and tended to keep to himself. At the age of 15 he got a nightshift job at a local computer company to financially help his family. In theory, he was employed as a computer operator, in practice he did the job of a security guard and was expected to watch over the computers but not touch them. As he had a lot of free time on the job, he studied the computers manuals, effectively becoming a self-taught expert, without even touching the machines. One day, he helped the company out of an emergency. They worked on an urgent project but ran out of punch cards. Clarence was the only one who knew how to recycle used punch cards. This was his first experience with computers and the turning point in his life. 

During his time at high school, Clarence attended summer school programs at local universities. His family could not afford for him to attend college, but fortunately Clarence managed to secure a scholarship and was able to start at Beloit College in 1960. He struggled at first, but thanks to his determination and hard work, he graduated in 1964. In 1969, he was awarded a PhD in computer science from University of Illinois. The title of his thesis was Probabilistic Languages and Automata.  


Ellis worked in both business and academic environment and on a diverse range of problems. From 1969 to 1972 Clarence Ellis worked at Bells Labs. After that he became an assistant professor at the University of Colorado Boulder, where his main focus was on operating systems research. The other places he worked at included IBM, Xerox PARC, Stanford University and Massachusetts Institute of Technology. He published over 100 papers and several books. He also worked as a guest lecturer at various points of his career, both in the United States and internationally in France, Ghana and Taiwan. In 1992 he returned to the University of Colorado Boulder, becoming an emeritus professor there in 2009. He also spent some time at Ashesi University in Ghana where he combined his interests in computer science and civil rights and worked on developing computer systems to simulate alternative forms of government for developing countries. He made notable contribution to developing “point and click” concept of clicking on the icons instead of typing codes, which is now used in Windows operating system. 


  • Clarence Ellis was a passionate civil rights activist. 
  • He was nicknamed “Skip”.