PURPOSE: To easily change the assignment of addresses without increasing the hardware quantity by storing previously the address identification information for identification of each peripheral equipment.

CONSTITUTION: The address identification information is previously stored in an address identification information storage part AM 4 serving as a part of a storage 1 so that the addresses included in the peripheral equipments 2-1 - 2-n are identified for each of these peripheral equipments. Then the storage contents of the AM 4 are read out when an address is designated by an address designation signal Sa given from a control part 3. Thus the selection signals Sc1 - Scn are produced and a peripheral equipment to which an address is designated can be correctly selected. Then it is possible to instantaneously cope with the change of specifications without changing the hardware constitution as long as the contents (combination of bits) of the address identification information stored in the AM 4 are previously changed in response to the change of the address assigning areas if caused by the change of specifications of the memory extended in a peripheral equipment.