Information About UPC Bar Codes
that when a UPC bar code is scanned at a store the correct price and product description will be pulled up from the store's computer system. So you can not just make up your own UPC bar code numbers. All UPC numbers must be assigned by one central agency.
Every retail product in North America, with the exception of books and pharmaceuticals, uses the UPC bar code system. Books use the Bookland (EAN-13) bar code system. Pharmaceuticals use the Pharmacode, also known as Pharmaceutical Binary Code. Note that mass market paperback books may have a Bookland and a UPC bar code on them to reduce scanning problems at retail stores. (Many retail stores can not scan Bookland bar codes.)
A UPC bar code must printed on every retail product sold in North America. The size of the bar code can vary from a maximum size of 1.5 inches wide by 1 inch in height down to a minimum of 1 inch in width by 1/4 inch in height. Also note that you need a minimum of 1/8 inch of clear space all around the bar code in order for a bar code scanner to properly recognize the bar code.
A UPC code is just an easy way for a computer to quickly look up the price of a product. The UPC code is used as an index into a data base to retrieve product information. Every unique product needs its own unique UPC code. UPC codes are only used in North America and are always 12 digits long. (11 digits plus a 1 digit checksum)
A UPC bar code is nothing more than an 11 digit number that is used to identify one specific product. For example, a 5 ounce bottle of hot sauce would have one UPC number and a 10 ounce bottle of the same hot sauce would have a different UPC number. They both contain the same product, but have different prices so they must have different UPC codes. Along the same lines, a 5 ounce bottle of medium hot sauce would have a different UPC number from a 5 ounce bottle of spicy hot sauce- since they are different items for the purpose of inventory in a store.
If you look at the example UPC bar code above you will notice that it actually has 12 digits in it. Where did the extra number come from? The last digit in this bar code, (7), is an extra digit called a checksum. The checksum character in a UPC bar code is calculated based on the first 11 digits and added to the end of the bar code. Every bar code scanner performs the same checksum calculation when it reads your bar code. It compares the result of its calculation to the checksum number it just read. If the two match, then the bar code has been read correctly. If they don't match an error has occurred and the bar code has not been correctly scanned.
Every product's UPC bar code is unique and will not be found on any other product anywhere in the world. Just like no two credit card numbers are the same, no two product UPC codes are ever the same. This ensures