"UPC" stands for Universal Product Code. UPC Codes are unique for each item and are widely used in retail stores in the United States for tracking merchandise from the time shipments are received to the time an item is sold. UPC codes can be typed in or scanned when items are received from manufacturers or sold to customers, to effectively add them to or remove them from inventory.

The Universal Product Code is a unique code for each item manufactured and sold by a retail store, which a store or distributor usually includes in a data base which also has the item description, manufacturer, supplier, last price paid, quantity ordered, quantity on hand, retail price and other information associated with the product.

The UPC code system was developed in the United States in 1973 by George J. Laurer, an IBM Engineer, along with the collective contributions of a group of grocery industry trade associations which formed the Uniform Grocery Product Code Council, consulting firm McKinsey & Company, and Ilhan Bilgutay who created the arrangement of bars of varying widths. UPC data structures are a component of Global Trade Item Numbers. All of these data structures follow the global GS1 standards.

An International alternate code is the European Article Number (EAN) standard which is a superset of the original 12-digit Universal Product Code (UPC) system developed in North America, adding an extra digit to the beginning so that there would be plenty of numbers for the entire world. The EAN-13 barcode is defined by the standards organization GS1. It is also called a Japanese Article Number (JAN) in Japan. UPC, EAN, and JAN numbers are collectively called Global Trade Item Numbers (GTIN), though they can be expressed in different types of barcodes. Since most scanners and registers worldwide can read both equally, most manufacturers in North America still use UPC.

Components of the UPC Code

A standard UPC code consists of a six digit manufacturer identification number, followed by a five digit item number and a check digit:

• The GS1 US, formerly the Uniform Code Council (UCC), issues the manufacturer a six digit manufacturer identification number. Each manufacturer pays a fee each year for the permission to use the UPC system. (The prefix 0 is reserved for UPC, the 13 digit EAN codes begin with a system code other than 0 which indicates the country the manufacturer is registered in and distinguish it from a UPC)
• A person employed by the manufacturer, called the UPC coordinator, is responsible for assigning five digit item numbers to products, making sure the same code is not used on more than one product.
• The last digit of the UPC code is called a check digit. This digit lets the scanner determine if it scanned the number correctly or not.

Determining the Check Digit

The check digit is calculated from the other 11 digits. As an example, using the code 63938200039 from "The Teenager's Guide to the Real World," the check digit is calculated by:

1. Add together the value of all of the digits in odd positions (digits 1, 3, 5, 7, 9 and 11).
   6 + 9 + 8 + 0 + 0 + 9 = 32
2. Multiply that number by 3.
   32 * 3 = 96
3. Add together the value of all of the digits in even positions (digits 2, 4, 6, 8 and 10).
   3 + 3 + 2 + 0 + 3 = 11
4. Add this sum to the value in step 2.
   96 + 11 = 107
5. Take the number in Step 4. To create the check digit, determine the number that, when added to the number in step 4, is a multiple of 10.
   107 + 3 = 110

In this example, the check digit is therefore 3.