Version A encodes a twelve-digit number. The first number encoded is the number system character, the next ten digits are the data characters, and the last digit is the check character.
The number system character is printed in human readable form to the left of the UPC symbol. Seven of the ten possible numbers have been assigned. For more information on the UPC-A barcode, view the following tutorial: UPC-EAN Check Digit
Version E allows zeros to be removed from the data to be encoded, resulting in a shorter tag. The encodation of the data characters is different than Version A.