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The Universal Product Code is a numerical only code. This code contains ten digits that may be of odd or even
parity that totals 20 unique patterns. (12 Numeric Digits) The two six digit halves are surrounded by left, center and
right guard patterns. The left half uses the odd parity encodations of digits, and the right half uses the even parity
encodations. The first digit of a UPC Version A code represents the number system. It indicates what type of
product the symbol is indicating. The next five digits comprise a code identifying the product’s manufacturer, and
the next five digits represent the product code. The final digit is a check digit whose value is mathematically based
on all of the other numbers coded in the symbol. A weighting scheme is used in its calculation, so that the check
digit also protects against transportation errors if the data is manually entered. A UPC Version A symbol is
arranged into two halves. Center guard bars separate the first and last six digits. Two left guard bars and two right
guard bars then enclose the two symbol halves. The various guard bars can be thought of as start and stop
patterns. The actual data is encoded as two bars and two spaces in a character that is seven modules wide. This
is called a 7,2 code that has 20 unique patterns.
