PURPOSE: To automatically delete unrequired records without increasing record length even when a record deletion period is set in the record.

CONSTITUTION: At the time of adjusting a PLU file 17-1, when the contents of a sales amount field inside the merchandise record are not updated for a prescribed period, a CPU 11 sets the record deletion period at the sales amount field. Also, the CPU 11 discriminates whether or not the record deletion period elapsed when the record deletion period is set at the sales amount field. As a result, when the record deletion period elapsed, the corresponding record to which the record deletion period is set is explained from the PLU file 17-1.