PURPOSE: To constitute the computer system which can support an under progressing keyboard type by adding a mechanism which dynamically change scan codes, of keys to a keyboard controller.

CONSTITUTION: The keyboard controller 12 receives a scan code switching command sent by a CPU 10, and a key number following it and a scan code corresponding to the key number through an input/output port, and the contents of a table memory stored with scan codes are updated on the basis of the number of a key switch as a key. When the key switch is pressed thereafter, a changed scan code (which may consist of plural bytes) corresponding to the pressed key switch is taken out of the scan code table memory and the contents are reported to the CPU 10.