A barcode symbol appears as alternating black vertical bars with white spaces. The numbers at the bottom of the symbol (called the human readable) represents the data encoded in the symbol. The numbers are made “machine readable” (able to be read by the bar code scanner) by representing the numbers by groups of different thickness bars and spaces. Special sets of bars provide start and stop signals to tell a scanner where it is reading within the code.
In the case of Universal Product Code or U.P.C. (the barcode you see on all of your grocery items) the data encoded in the bars and spaces is put together in a very specific way. There are three elements to this “data string”; a company prefix, an item reference and a check digit. The company prefix (called a U.P.C. Company Prefix when being used to build a U.P.C.) is assigned to your company by GS1 US - each company prefix is unique, completely different and is associated with a brand owner as this helps ensure your product’s bar code is not confused with another company’s product.
The next element is called an item reference, and it is a number assigned by your company. When you combine your U.P.C. Company Prefix and your item reference, it will always total 11 digits. The item reference number can be 1 digit or up to 5 digits, depending upon the number of digits in your U.P.C. Company Prefix. These 11 digits are then used to calculate a data check digit, the 12th and last digit encoded into your U.P.C. bar code. The data check digit is there to ensure data accuracy.
U.S. organizations that need a U.P.C. can have a U.P.C. Company Prefix assigned by contacting GS1 US and joining Partner Connections. As a benefit of membership, you will also receive access to the Data Driver™ tool which helps you create and manage your barcodes, so each product is given a globally unique number. Data Driver automates the process of printing barcode labels and ensures your barcode will meet the required quality and accuracy requirements of your retailer.