"A barcode is an optical representation of data that is printed as a machine-readable pattern. Product barcodes, such as the UPC and EAN codes (see Figure 1.0) that are common in retail, are printed either directly on a product, a product label, the retail shelf or the product’s packaging.
Widely used linear barcodes, such as the UPC and EAN product codes, are comprised of a sequence of vertical lines and spaces designed to be read by a barcode reader programmed to extract (or ‘decode’) the data that the barcode pattern contains for direct input into a Point of Sale (POS) register without the need for human keyed entry.
Barcodes were first used to automate the tracking of railroad cars, but were then widely adopted for consumer products when they were first used to automate supermarket checkout systems to reduce the error associated with manual keying at checkout and to automate inventory management."
