PURPOSE: To provide the titled system with a static auxiliary storage device to transfer a program or data from an ordinary auxiliary storage device to the static auxiliary storage device at the initialization of the computer and access the statis auxiliary storage device at the execution of operation.

CONSTITUTION: An arithmetic controller 1 and a main storage device 2 are connected each other through a high speed bus 11 and a static auxiliary storage device 21 consisting of a semiconductor bulk memory is connected to the bus 11 through an interface 20. In addition an ordinary auxiliary storage device 23 is also conneted to the bus 11 through an iterface 22. The auxiliary storage device 23 is constituted by a magnetic drum unit or a magnetic disc unit. On the ther hand, an I/O bus 10 is connected to the aritmetic controller 1. A peripheral device 9 and a process I/O unit 4 are connected to the I/O bus 10 through an I/O interface 8 and a process I/O interface 3 respectively and the process I/O unit 4 is connected to a power generation plant 7 through a detector 5 and an actuator 6.