The bar code you see on most retail products in the United States and Canada is called UPC-A, which stands for universal product code. The number consists of 12 digits. According to the geek camel, the first number indicates which category the product belongs to; For example, the number 3 represents health-related items, while the number 2 is used for some weighing products, such as meat.
The next five numbers will tell you which company made the product (that is, if you happen to remember a long list of UPC identification numbers of manufacturers). There is usually a space between this number and the next five-digit block, which corresponds to a specific product.
The last bit is the so-called parity bit, which is used by the computer to verify whether all other numbers in the code have been scanned or entered correctly. The parity bit is calculated according to a formula that uses all the numbers listed before it. To simplify this process, suppose you are dealing with a three-digit number; The last digit is the parity bit, which can be found by taking the difference between the first two digits. For example, if these numbers are 4 and 3, then your parity bit is 1. If the cashier accidentally enters 42 1 instead of 43 1, the system will realize that the parity bit does not match the formula and will give some kind of error alarm.
Of course, UPC-A barcode is not the only barcode that exists. According to BizFluent, UPC-E barcodes are used for commodities that are too small to accommodate the lengthy 12-digit barcode, which combines category, manufacturer and product information into six digits. The EAN- 13 barcodes used all over the world contain the same information as UPC-A barcodes, but they also contain numbers corresponding to the countries where barcodes are registered. Books, mails, music scores, etc. There are also different types of bar codes.