PURPOSE: To easily display a storage content by reading out and displaying data from a memory device setting the fact that power supply from a solar battery to a processor is started as a start-up condition.

CONSTITUTION: The identification name of the data, etc., is stored in the memory 3 of a memory card 7. When light is projected on the solar battery 1, power is supplied to a display device 4, the memory 3, and a data processor 2, respectively by the electromotive force of the battery. The processor 2 reads out identification information corresponding to the identification name, etc., from the area of the memory 3 setting the start of the power supply from the solar battery 1 to the processor 2 as the start-up condition, and displays it on the display device 4.