PURPOSE: To perform the initialization only with a volatile memory for the initialization of a memory device obtained from a combination of the volatile and nonvolatile memory modules, by transmitting an inhibition signal to the nonvolatile memory module to discontinue the writing and reading of data.

CONSTITUTION: An inhibition signal is transmitted to a control line 102 from a control module 10 prior to an initialization. Then nonvolatile memory modules 30 and 31 discontinue their reading/writing actions with said inhibition signal. The module 10 writes the zero value to memory modules 20, 21, 30 and 31 respectively while it is delivering the inhibition signal. In this case, however, the writing is actually carried out only to the modules 20 and 21. Thus the module 10 discontinue the generation of the inhibition signal after the initialization is through with the volatile module. As a result, a memory device containing both volatile and nonvolatile memories can have a smooth actuation in case the power is supplied again after the external power supply is stopped.