With a temporary operating unit being operating, a user provides a boot timing using a boot timing instructing unit. This causes a CPU to compute a boot preparation timing based on the boot timing, and store the boot timing and boot preparation timing to a boot timing memory. At this time, a timer begins a time-keeping operation. After that, the user turns off the power to the temporary operating unit. A boot preparation instructing unit determines whether or not the time being measured by the timer coincides with the boot preparation timing stored in the boot timing memory. When the time measured by the timer coincides with the boot preparation timing stored in the boot timing memory, the boot preparation instructing unit provides the CPU with a boot preparation instruction. This turns on the power to the temporary operating unit, and the CPU performs a boot preparation.