Overview  |  Anatomy of a Bar Code  |  Bar Code Symbologies
How to read a Bar Code  |  Terms & Abbreviations

Each digit of this twelve digit UPC bar code is divided into seven miniature pieces (modules) including two characters beyond the ten needed to encode the UPC. (See Symbologies for additional information on UPC bar codes.)

2.  Each piece is coded as either a black or dark module represented by a one (1) in binary code; or a white or light module represented by a zero (0).

3. Start with the first module (black) and write down a one; second module (white), write down a zero, third module, a one; for the fourth module, write down a zero and continue with all twelve digits.

4. To get the UPC code, match your list of zeros and ones with the UPC Key Code. Use the Left Code list until you get to the sixth digit, then use the Right Code list. (The mirror image coding permits bi-directional scanning.) You should have a list similar to the following:

Left guard pattern 101

1 0001101

2 0011001

3 0111101

4 0100011

5 0110001

Center guard bar pattern 0101

6 1010000

7 1000100

8 1001000

9 1110100

0 1110010

Modulus check digit 1001110 (5)

Right guard bar pattern 101