check digit (checksum character)

A check digit, also known as a checksum character, is the number located on the far right side of a bar code. The purpose of a check digit is to verify that the information on the barcode has been entered correctly. The barcode reader's decoder calculates the checksum by performing a series of mathematical operations on the digits that precede the check digit, and comparing the result of the calculation to the value of the check digit. Typically, if the check digit matches the result of the calculation, the reader emits a signal (such as a beep) to acknowledge that the results match, and the scan has been successful.