To lower the cost, to improve the start-up reliability, and to make the equipment small-sized by using an inexpensive and small storage medium like a ROM as an auxiliary storage medium for starting.

An environment file is provided on a ROM disk 6 and in a RAM area 4. When sector data are read out by disk access 1 at the time of starting, a sector data position managing function 2 checks whether or not the stored sector data of the environment file are being read out and when not, data are read out of the ROM disk 3 and returned to the disk access 1. When the sector data are being read out, it is judged through a specific key depression check 5 whether or not a specific key is pressed and when the specific key is not pressed, data are read out of the RAM area 4, but when the specific key is pressed, data are read out of the ROM disk 3 and returned to the disk access 1.