Complex sentence: Mitchell began working with computers in 1962 while a student at the University of Waterloo where he and three other undergraduates developed the first WATFOR compiler, a fast FORTRAN compiler for the IBM System/360 family of computers.
Split into simpler sentences: Mitchell began working with computers in 1962 while a student at the University of Waterloo. He and three other undergraduates developed a fast compiler for the Fortran programming language on the IBM System/360 family of computers.