When he was leaving high school, Corneil was told by his English teacher that doing a degree in mathematics and physics was a bad idea, and that the best he could hope for was to go to a technical college. His interest in computer science began when, as an undergraduate student at Queens College, he heard that a computer was purchased by the London Life insurance company in London, Ontario, where his father worked. As a freshman, he took a summer job operating the UNIVAC Mark II at the company. One of his main responsibilities was to operate a printer. An opportunity for a programming job with the company sponsoring his college scholarship appeared soon after. It was a chance that Corneil jumped at after being denied a similar position at London Life. There was an initial mix-up at his job as his overseer thought that he knew how to program the UNIVAC Mark II, and so he would easily transition to doing the same for the company's newly acquired IBM 1401 machine. However, Corneil did not have the assumed programming background. Thus, in the two-week window that Corneil had been given to learn how to grasp programming the IBM 1401, he learned how to write code from scratch by relying heavily on the instruction manual. This experience pushed him further on his way as did a number of projects he worked on in that position later on. Corneil went on to earn a bachelor's degree in mathematics and physics from Queen's University in 1964. Initially he had planned to do his graduate studies before becoming a high school teacher, but his acceptance into the brand new graduate program in computer science at the University of Toronto changed that. At the University of Toronto, Corneil earned a master's degree and then in 1968 a doctorate in computer science under the supervision of Calvin Gotlieb. It was during this time that Corneil became interested in graph theory. He and Gotlieb eventually became good friends. After postdoctoral studies at the Eindhoven University of Technology, Corneil returned to Toronto as a faculty member in 1970. Before his retirement in 2010, Corneil held many positions at the University of Toronto, including Department Chair of the Computer Science department, Director of Research Initiatives of the Faculty of Arts and Science, and Acting Vice President of Research and International Relations. During his time as a professor, he was also a visiting professor at universities such as the University of British Columbia, Simon Fraser University, the Université de Grenoble and the Université de Montpellier.
Work
Corneil did his research in algorithmic graph theory and graph theory in general. He has overseen 49 theses and published over 100 papers on his own or with co-authors. These papers include: As a professor emeritus, Corneil still does research and is also an editor of several publications such as Ars Combinatoria and SIAM Monographs on Discrete Mathematics and Applications.