Almost everything that we buy at a store now has a bar code on it. The patterns of black and white lines on a bar code are like a message written in a secret code. To decode the message we need special equipment. When we go through a checkout at a store the cashier uses a bar code reader to check the price of everything we buy. The bar code reader decodes the data on a bar code. Bar code readers scan the bar codes and send the information to a computer. The computer then tells the cashier what the price is. Some scanners use a laser thatis able to read the pattern of white and black lines on the bar code.