given to objects to which supply of clock and power are controlled a device management table 150 is provided corresponding to each hardware device to which the device number 142 is allocated as shown in fig7 b these hardware devices are classified into two groups in view of power consumption control the first group comprises lsis such as the dmac 4 the vram 6 and fdc 10 which require power supply for holding internal chip states and whose power consumption can be considerably reduced by stopping the supply of clock and devices such as the fdd 11 bl 9 and mu 15 the power consumption of which can be reduced merely by turning off the power supply the field of clock stop flag 151 and power supply stop flag 152 control these devices respective flags represent whether or not the clock or the power source may be turned off when the hardware is not used the values 34 0 34 and 34 1 34 represents 34 no permission 34 and 34 permission 34 respectively on the other hand the second group comprises devices such as the cpu 1 and peripheral lsis the clock or the power source of which may be turned off immediately if the hardware device is not used devices such as the fdd 11 which may consume a lot of power upon reactivation if it is frequently turned off and devices such as the lcdc 7 lcd 8 and bl 9 the clock or the power source should be turned off after confirming that they will not be used for a given period time the reason for this being.