What is a barcode?

A standard barcode is typically composed of a series of black lines (also called bars) and white gaps, each with varied widths. Numbers, letters and other characters can be represented by combining the widths of bars and spaces into elements. Barcodes are typically generated by a barcode maker and printed by a label printer onto barcode labels. A barcode scanner is typically used to read the information stored in a barcode. The scanner provides a light source which is absorbed by the black bars and reflected back to a sensor by the white spaces. As the bars vary in width, the length of the electrical signal generated by the scanner can be visualised as a wave form. The patterns in the wave form can be decoded by the barcode reader’s decoder. The data is then typically passed to a computer in a computer format such as ASCII. There are now many devices that can decode barcodes varying from the traditional handheld barcode scanner and computer scanners to mobile phones. The data stored in the barcode is then processed by barcode software on a computer or a barcode system. Both Tesco and Amazon provide phone applications that can be used to read data stored in a barcode.

There are many types of barcodes that are used to represent different types of data. Some barcodes only contain numeric data, others alphanumeric. Some allow many characters to be stored while others store just a few. An example of a standard barcode is EAN 13 (the European Article Number barcode) which has been renamed the International Article Number. This type of barcode is used world-wide for marking retail goods. The first two or three letters of an EAN 13 comprise of a country code representing where the product is registered, the next nine or ten digits contain data about the product and the final digit is used as a checksum to ensure the data has been transmitted correctly. An alternative barcode used mainly in US and Canada retail stores is the UPC code (Universal Product Code). Many types of barcodes have been superseded but are still in use by some industries.

Barcodes were first used to label rail road cars. They did not become commercially successful until adopted by supermarkets for labelling products in checkout systems. Despite recent competition from Radio Frequency Identification tags barcodes remain the cheapest method of identifying products and commodities and are likely to remain in use for some time to come.