To reduce the size of the computer so that the memory capacity is still large by using an EEPROM, which stores data and functions as a work memory and a mass memory, for computer data as a NAND EEPROM or NOR EEPROM.

This computer includes main memories b1-bn and the work memory, and the main memories b1-bn which are generally disk memories are used to store all data and programs. There, the main memories b1-bn are composed of electrically erasable nonvolatile semiconductor memories EEPROM; and the semiconductor EEPROMs are used even as the work memory and a controller EE-S is assigned to semiconductor memories (NAND EEPROM) so as to control the input and output of data of ≥1 semiconductor memory EEPROM. Or the semiconductor memories EEPROMs are composed of NOR EEPROMs.