O'Rear planned to be a physical education teacher, but later ended up graduating from the University of Texas at El Paso with a bachelor's degree in mathematics.
In 1966, TRW in Redondo Beach hired O'Rear to work on Air Force spy satellite programs.
Later in the 1970s, O'Rear and a friend from his TRW days founded a company called Texametrics that made automated machinery for the manufacturing of polyurethane bottle caps.
Work then began as soon as the first prototype of the IBM PC was received in Thanksgiving of 1980, and O'Rear was assigned both project lead and sole programmer.
Despite difficulties with both hardware and software (and some communication delays with IBM), O'Rear produced PC DOS v1.0 in August 1981.