PURPOSE: To control a data area by setting an area whose reading and writing are performed on a device side automatically when the capacity of a memory is extended optionally.
CONSTITUTION: A processor 1 executes a control program in a main memory 4. The processor 1 reads information on the connection of an extension memory 5 from a connector through a bus 6 by the system generating program in the head of the control program. If the extension memory 5 is not connected, the processor 1 allows a data area 4b in the memory 4 other than a preset program area 4a to be read and written. When the extension memory 5 is connected, the data area 4b of the main memory 4 and the whole area of the extension memory 5 are permitted to be read and written. Thus, a readable and writable area is set according to the capacity of the memory and then prescribed processing is performed.
TANAKA KUNIO
TAKEGAHARA TAKASHI
