The Uniform Code Council in the US, along with the international article numbering authority, EAN International, allocate blocks of unique 12 or 13-digit numbers to member companies through a national numbering authority. In Britain this is the Article Number Association. These numbers are shown as bar codes, and all of the information about a product is held on a database. The numbers have no meaning, not even the country of origin of the product, and are often allocated in strict numerical order to identify each different product. The bar codes are then printed to international standards so that they can be scanned successfully and decoded throughout the world.
Some retail stores operate internal systems that use eight-digit bar codes.
The bar codes begin with either 0 or 2, and are not unique. Your previous correspondent who wrote concerning supermarket bar codes tells only part of the story. It is hard to summarise bar code specification in a few words, but here goes . . . The supermarket bar code is called an EAN bar code. This European Article Numbering association code has been adopted almost worldwide.