debugger

noun

1. A computer program that helps the user to test and debug other programs, by enabling their step-by-step execution controlled by the user, setting of breakpoints, and monitoring values of variables.

   “6. Memorandum PDP-23, ID Invisible Debugger, August 20, 1964.”

   “Invisible Debugger, commonly referred to as ID, a utility program in the PDP-1 time sharing system written to aid in the debugging of other programs. An advanced ID has been written (April, 1966) to allow all operations to be carried out either directly on drum fields or on running cores.”