Microprogram load unit

A microprogram load unit comprising a readable and writable microprogram memory within a central processor unit for storing microprogram, a relatively low speed, readable and writable, nonvolatile memory unit, and a readable and writable memory with battery backup. It is determined whether data of the readable and writable memory with backup has been lost or not when power is turned on. If data loss is not present, microprogram is read out of the readable and writable memory with backup and written into the microprogram memory. If data loss is present, microprogram is read out of the nonvolatile memory unit and is written into the microprogram memory.