PURPOSE: To improve the operability by changing procedures of boot priority based on input or non-input of a specific key at the time of executing a set-up program.

CONSTITUTION: At the time of setting up a system, it is judged whether the specific key is inputted from a keyboard 9 or not, and boot processing procedures stored in a memory 15 are changed based on the result of judgment. As the result, the boot priority is momently changed at the time of set-up. Thus, menu setting for operator's troublesome boot priority change is omitted, and the boot priority is easily changed at the time of setting up the system, and the convenience of use is improved.