PURPOSE: To provide a resuming function for surely reproducing a former state at high speed at the time of restarting work.

CONSTITUTION: When a resuming switch 7 is pressed at the time of ending the work, a resuming controller 8 complets processing thus for, afterwards, preserves the contents of a main storage device 1 in a hard disk device 2 by using a system managing device 9 and further turns off the other power sources while turning on the power source of the main memory by controlling a power unit 3. On the other hand, when the switch 7 is pressed at the time of restarting the work, the resuming controller 8 discriminates whether information inside the main storage device 1 is lost or not depending on whether the OFF of the main memory power source is detected by a main memory power source OFF detector 6 or not and when the information is not lost, original processing is immediately restarted according to the information inside the main storage device 1 or when the information is lost, the original processing is restarted after the contents in the main storage device 1 are restored by transferring the preserved contents in the hard disk device 2 to the main storage device 1 while using the system managing device 9.