Modern supermarkets and stores utilise electronic cash registers more often than not. Each purchasable item has a bar code printed on the packaging. This bar code information can be read by a laser scanner, which transfers it to a computer controlled till. As well as the computer supplying the detail and price of that particular good, it can also total the bill. All of this information is fed to the till which can then print out a receipt. The computer has the additional benefit of being able to record the sale for stock keeping purposes.
Common bar codes are European Article Numbers (EAN), based on a figure with 13 numbers and the Universal Product Code (UPC), based on a number with 12 digits. Each digit is depicted by a row of parallel straight lines and white spaces. The laser scanner converts the information into binary digit signals and then sends the results to the computer.
The laser scans the bar code with a beam of light transmitted from one end of the code to the other. This laser is sensitive enough to read the code from either left to right, or right to left. The bar codes are generally black on a white background, but the laser can operate on any dark colour, with the background being any pale colour.
The bar code gives the manufacturer information on the goods and the size of the package. As a safety measure, a security code is included to prevent any alterations being made or a scanner misread.
