The Universal Product Code (UPC) bar code version A is a fixed length (12 characters) bar code scheme designed to uniquely identify a product and its manufacturer. The first digit in a UPC-A symbol is the number system digit, the next ten digits are data characters, and the last digit is the checksum. This is the standard bar code scheme for items of sale to the public. Note that supplementals are not supported.

A UPC-A bar code consists of the following elements:

• Left guard pattern
• Number system digit (encoded in odd parity)
• Manufacturer's code (encoded in odd parity)
• Center guard pattern
• Product code (encoded in even parity)
• Check digit (encoded in even parity)
• Right guard pattern

UPC-A uses a different coding scheme for the first half of a symbol (number system digit and manufacturer's code) and the second half of a symbol (product code and check digit). The left half uses the odd parity encodation digits and the right half uses the even parity encodation digits.

An example of a UPC-A bar code is shown here.