POS SYSTEM

PROBLEM TO BE SOLVED: To eliminate the waiting time of a customer kept in a transaction mode and also to attain the effective use of the memory capacity where the characteristic of transaction data, etc., are reflected by notifying the replacement of storage media when the remaining idle capacity of a storage medium is smaller than the largest data length of a transaction data history. SOLUTION: A storage medium replacement decision device 14 receives the input data via a data input means 15, measures the data length in every transaction, and updates the targest data length memory 17, based on the measured data length. An idle capacity count means 19 measures the remaining idle capacity of a storage medium, based on the remaining idle capacity information received from an auxiliary storage 12. A medium replacement decision means 20 compares the remaining idle capacity with the data length of the memory 17. When the idle capacity is smaller than the data length, the warning is given to a medium replacement warning device 13 for the replacement of media. Then the replacement of media is carried out before a transaction is started. Thus a transaction task is never interrupted and the waiting time of customers can be eliminated.