To enable a user to select the utilizing style of a backup battery.

Concerning portable information equipment provided with a main battery 11 and a backup battery 12, when it is detected that the remaining capacity of the main battery 11 is less than a prescribed level, either a mode 1 for holding contents in a RAM 3 or a mode 2 not to hold them is selected by the backup battery 12 and when it is detected by checking the terminal voltage of the main battery 11 detected by an A/D converter 13 that the remaining capacity of the main battery 11 gets the level less than a prescribed one, an alarm message is displayed on a liquid crystal display(LCD) 6. At the same time, corresponding to any selected one of modes 1 and 2, the contents in the memory are held while controlling the supply of power to the RAM 3 through a power source control circuit 10.