The Universal Product Code (UPC)is a convenient label that identifies each item in a store through a series of easy-to-understand numbers.
Since a cashier has to scan the UPC to charge $1.99 for a box of cereal, it might seem like the UPC is associated with the price of an item, that all of those numbers add up to a code that equals $1.99 at the register. Actually, the UPC has nothing to do with a specific price. The UPC actually identifies the item itself. When the UPC is scanned at the register, the store's central computer recognizes the item and sends the current price back to the register. This way, when a price changes, workers don't have to mark every single product, they just have to change the number in the central computer.
NUMBERS
Each number in the UPC is significant. Let's look at the UPC 6 52156 00018 4 as an example.
The first number is the number system character. It helps the computer know what kind of UPC it is dealing with. If the number is 0, 6 or 7, it's a standard UPC. If it's a 2, then the item is priced by weight, such as meat or produce. If the number is a 3, then the product is from the pharmacy. A 4 is reserved for stores so that they can make up their own UPC codes for things like gift certificates that are only sold in their stores. If the first number is 5, then the UPC comes from a coupon.
The next block of five numbers, along with the number system characters, is the manufacturer identification number. Each manufacturer is assigned its own number.
The second block of five numbers is the item number. Every single product must have a different item number. Assigning these numbers is a complicated job because not only does each brand need a different number, but each size and packaging variation. So a 12 oz. can, 20 oz. bottle, 2-liter bottle, 12 pack and 24 pack of the same particular type of cola must all have different item numbers.
The final number is the check digit. It's a final test to make sure the UPC has scanned properly. First, consider the first 11 digits of the UPC and add the numbers in odd positions (1st, 3rd, etc.). Multiply that number by 3. Remember that number. Then, add the numbers in even positions. Add this result to the first number you figured out. The check digit is the number that you would need to add to your final result to end up with a multiple of 10.
Most UPCs contain 12 digits. However, you will also see UPCs with fewer numbers. These smaller numbers come from manufacturers with several zeros in their identification numbers. If there are four zeroes in a row in a UPC, they can be dropped, resulting in an 8-digit UPC.
BARS
The actual bar codes that cashiers scan at the register are a translation of the numbered code. The black bars and white spaces can be one, two, three or four spaces thick. Each number is represented by a certain pattern, with each number representing the thickness of the spaces and bars above it. For instance, a zero is represented as 3-2-1-1 and a six as 1-1-1-4. A pattern of bar, space, bar, each one space thick, will always appear at the beginning, middle and end of a UPC.
They may perform a complicated job, but when they're broken down, UPCs are actually quite simple and understandable. So the next time you go shopping, take a moment to think about the UPCs that make checkout so convenient.
