PURPOSE: To discriminate an abnormal display with easiness to see through simple constitution, by discriminating and displaying the occurrence of the overflow and underflow of information on a unit price, weight, price, etc., stored in a memory part.

CONSTITUTION: On every transaction, a balance digital value from weight register 3, a digital set unit price from unit-price setting part 7 via unit-price register 8, etc., a digital price from arithmetic part 4, etc., are stored in memory part 6. On the basis of its memory contents, arithmetic part 4 discriminates the overflow that the memory information exceeds the number of display digits and the underflow that the display is minus, and if either one is occurring, display contents set by symbol setting part 9 drive display fields 11W13 of display part 10 via display change-over part 5. Consequently, display segments 14b, 14d, etc., of display fields 11W13 display OF for the overflow and UF for the underflow. Therefore, the simple constitution provides the abnormal display easy-to-see, which is discriminated without being missed.