PURPOSE: To unnecessitate the input of an ID code from an outside in the case of personal identification at a personal computer.

CONSTITUTION: A keyboard keying detection part 1 recognizes and codes a depressed key. The ID code is built in a ROM 4 beforehand. An ID code generation part 2 reads the ID code from the ROM 4. When the keyboard is connected, a keyboard control part 3 reports the ID code read through the ID code generation part 2 and the key coded by the keyboard keying detection part 1 to the personal computer.