There is nothing mysterious about barcodes. A barcode is simply a representation of a group of letters and numbers that are designed to be read by a computer, not a person. A barcode is always used as part of a large system. For example, in retail applications the barcode is scanned at the checkout counter. The terminal at the checkout counter is connected to a computer that reads the barcode, compares it to the stored product number, and sends the price information to the terminal. In more involved systems, the computer calculates inventory and can even automatically reorder merchandise. Many different forms of barcodes exist. UPC-A, which is used in supermarkets and drug stores and is familiar to most consumers, is always a 12-digit code. It looks like this.

The first number indicates the type of product, digits 2 through 6 are assigned to a specific company, and digits 7 through 11 are unique for each product the company produces. The last digit is a check digit to make sure that the barcode has been produced accurately. Another popular barcode is called Code 128.

The code can contain both numbers and letters and can be unlimited in length. It is often used on shipping container labels and where a great deal of information must be captured. The major concern when producing a barcode is legibility. If the barcode cannot be read properly, the entire system, of which it is a part, fails. In fact, retailers often charge suppliers large penalties if the barcode on their product cannot be scanned easily. The four elements needed to produce bar codes are a printer, software, labels and ribbons