Abstract: The POS system has at least one POS terminal (101) and a store controller (121) connected to the POS terminal. The POS terminal has a program storage device (107), a program updating device (106), a program executing device (106), a goods information storage device (107) and a goods information updating device (106). The program storage device and the goods information storage device serve to store data in a non-volatile storage device. When the POS terminal (101) is started up, the program updating device and the goods information updating device operate to compare the data stored in the non-volatile storage device (107) and the data stored in the store controller (121).