Abstract: A circuit for initializing a digital computer. Whenever an operator turns on a power supply for the digital computer or activates a console switch, the circuit transmits overriding address signals. These signals divert the digital computer from a normal initializing routine to a routine provided by the initializing circuit. The routine in the initializing circuit includes digital computer instruction sequences for performing preliminary diagnostic operations and for transferring instructions to a main memory from preselected peripherals. When the routine is complete, the computer is prepared to process other programs and to operate with other peripherals.