hello
A UPC symbol is a series of thick and thin lines stamped on packages, readable by laser scanners. Some may refer to this area as a bar code. 'UPC' stands for Universal Product Code: a standardized means of identifying the manufacturer and the specific description of the product. A UPC symbol allows different retailers to keep track of the products they receive from the same manufacturers and vendors. Every manufacturer is identified by the first five numbers scanned on the UPC symbol, and the specific product is identified by the next set of numbers. A special number called a 'check code' is added to thwart the use of a counterfeit UPC symbol. Even if a hacker discovered the codes for the manufacturer and the product, the secret check code number must match precisely.
thanks