David was born and raised in Terre Haute, Indiana, the son of Arthur and Norma Lolli Rennels. After graduating from Rose Hulman Institute, of Technology, summa cum laude(1964), he then moved to California, earning a master's degree at California Institute of Technology(1965) and a PhD from UCLA(1973). He was a 1st LT in the US Army during the Vietnam War(1966-1968.) He was a computer scientist and a UCLA professor emeritus. He and ‪Algirdas Avižienis‬ designed the STAR(self testing and repairing) computer hardware for long term space craft at JPL/CalTech. He was vice chair of undergraduate affairs in the computer science department at UCLA. David was employed by the Jet Propulsion Laboratory/Caltech, and UCLA. He is survived by his son, Marc Rennels, his sister, Kay Bolinger, and his niece, Ashley Luebke.