PURPOSE: To shorten a time until program loading is completed by inputting the loading start address of a program and program length, initializing a main memory device at every initializing unit byte, and performing the program loading from an initialized memory area.

CONSTITUTION: An input means 1 to input the loading start address of the program and the program length from an auxiliary memory device 6, an initializing means 2 to initialize the main memory device 5 at every initializing unit byte, and a readout means 3 to start up readout by initialization completion unit bytes from the auxiliary memory device 6 to the initialized memory area are provided. Also, a program loading completion judging means 4 to judge whether or not the readout by program length from the auxiliary memory device 6 is executed is provided. In such a way, it is possible to shorten the time required for the program loading by performing initialization from the loading start address of the program and loading the program from an area whose initialization is completed.