Composite bar codes
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c Product Code: The product code is a unique code assigned by the manufacturer. Unlike
the manufacturer code, which must be assigned by the UCC, the manufacturer is free to
assign product codes to each of their products without consulting any other organization.
Note: The product code is usually printed below the bar code.
d Check Digit: The check digit is an additional digit used to verify that a bar code has been
scanned correctly. Since a scan can produce incorrect data due to inconsistent scanning
speed, print imperfections, or a host of other problems, it is useful to verify that the rest of
the data in the bar code has been correctly interpreted. The check digit is calculated
based on the rest of the digits of the bar code. Normally, if the check digit is the same as
the value of the check digit based on the data that has been scanned, then there is a high
level of confidence that the bar code was scanned correctly.
Note: The check digit is usually printed to the right of the bar code.
2 UPC-E (including +2 and +5 variants)
UPC-E is a variation of UPC-A which allows for a more compact bar code by eliminating extra
zeros. Since the resulting UPC-E bar code is about half the size as an UPC-A bar code,
UPC-E is generally used on products with very small packaging where a full UPC-A bar code
cannot reasonably fit.
A UPC-E code contains the following:
• Left-hand guard bars, or start sentinel, encoded as 101
• Six data characters, encoded from the parity table above
• Right-hand guard bars, encoded as 010101 (a center-guard bar pattern with a trailing
bar)
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