PURPOSE: To enable continuous utilization of a portable computer without preparing many substitutive battries at a place where commercial power is not available can not be obtained.

CONSTITUTION: Energy is stored in a spiral spring or the like as a mechanical form and the mechanical energy is transduced into electric energy and supplied to a semiconductor circuit element such as a CPU 110. A means 90 for detecting/warning an energy accumulation lost state such as the full released state of the spiral spring is connected and when a user winds up the spiral spring or the like in accordance with the warning, the computer can be continuously used. Since the CPU 110 is reset by detecting the full release of the spiral sping and the reset state of the CPU 110 is released by detecting the full winding of the spiral spring, the CPU 110 can be prevented from generating an unstable operation and the computer can surely be used.