PURPOSE: To easily deal with the composition of inputs by allocating the pre scribed area of a RAM provided on the bus of a microcomputer to output signals from the keys of a keyboard composed of the plural keys.

CONSTITUTION: The prescribed area of the RAM provided on the bus of a microcomputer 14 is allocated to the output signals from the keys of the keyboard composed of the plural keys. Namely, since a key scan unit 12 is provided out of the microcomputer 14 and the prescribed area of the RAM is allocated to the output signals from the keys of the keyboard, a software program for key scan is unnecessitated. Thus, it is not necessary to conventionally prepare the software for key scan, the amount of the program is more reduced, and the composition of inputs, namely, the key inputs, remote control inputs and home bus inputs of the microcomputer can be easily dealt with. Further, an interface part to be used by a user can be unified.