PURPOSE: To detect an error at the time or partial update or data in a record recorded in a peripheral storage device.

CONSTITUTION: An updated record 306 is read out of the peripheral storage device 203 and held at a data holding part 202, an unupdated part in this record is outputted to a signal line 304, and a check code which is part of this part is outputted from a signal line 303. An input data holding part 200 inputs update data 301, generates a check code for the check code 303 and updated data, and also outputs the updated data to a signal line 302. A write data check code addition part 201 generates write data 305 from the updated data 302 and unupdated part 304 and also generates a check code for the part corresponding to the part that the input data holding part 200 generates the check code for from the write data 305; and the check code is compared with the check code generated by the input data holding part 200 to confirm normal operation.