David J. Bradley (born 4 January 1949) is one of the twelve engineers who worked on the original IBM PC, developing the computer's ROM BIOS code. Bradley is credited for implementing the "Control-Alt-Delete" (Ctrl-Alt-Del) key combination that was used to reboot the computer. Bradley joined IBM in 1975 after earning his doctorate in electrical engineering from Purdue University with a dissertation on computer architectures. Education Bachelors, Electrical Engineering, University of Dayton (Ohio), 1971. Master of Science, Electrical Engineering, Purdue University, 1972. PhD, Electrical Engineering, Purdue University, 1975. Control-Alt-Delete According to Bradley, Control-Alt-Delete was not intended to be used by end users, originally—it was meant to be used by people writing programs or documentation, so that they could reboot their computers without powering them down. This was useful since after a computer was powered down, it was necessary to wait a few seconds before powering it up again to avoid potential damage to the power supply and hard drive. Since software developers and technical writers would need to restart a computer many times, this key combination was a big time-saver. David Bradley and Mel Hallerman chose this key combination because it is practically impossible to accidentally press this combination of keys on a standard original IBM PC keyboard. However, the key combination was described in IBM's technical reference documentation and thereby revealed to the general public. At the 20th anniversary of the IBM PC on August 8, 2001 at The Tech Museum, while on a panel with Bill Gates, Bradley said, "I have to share the credit. I may have invented it [Control-Alt-Delete], but I think Bill made it famous." Multiple-key reboot had been introduced by Exidy, Inc., in 1978, for its Sorcerer Z80 computer. It provided two Reset buttons, which must be pressed simultaneously to achieve reboot. In March 1980, the multiple-key reboot concept had been introduced for the Apple II by Videx in its VideoTerm display card add-on, requiring Control-Reset, rather than Reset alone, to reboot the machine. The innovation was noted and well received at the time. Other accomplishments Bradley is the author of Assembly Language Programming for the IBM Personal Computer (Simon & Schuster, , January 1984), also released in French as Assembleur sur IBM PC (Dunod, ), Russian ("Radio" Publishing House, Moscow), and Bulgarian ("Technica" Publishing house, 1989). Bradley holds seven U.S. patents. Bradley has been adjunct professor of electrical and computer engineering at Florida Atlantic