I actually worked at a retail store for many years. When we implemented our bar code readers it was to read UPC codes of products. Our computer system would recognize the UPC and be able to then give the price we had assigned to the product. Each product has a unique UPC.
The bar code reader is used to read printed bar codes. It allows an attached computer to identify a product or item on which a bar code it printed and, most importantly, price that item to automate and speed checkout in a store or market.
Input - the reader is reading the bar code and putting the information into the computer
a scanner, or gun.
Bar code reader
your head
Different bar code readers can be installed using Google's Play Store. The store offers a wide range of bar code scanners such as "Bar code Scanner from ZXing Team or Google's own implementation of a qr/bar code reader : Google Goggles.
There's an app for that
bar code reader
There are several companies that make hand held bar code readers. You can even get an app for your smart phone that will read bar codes. A major manufacturer of bar code reader is Motorola (they bought "Symbol" the leading bar code reader company a while back). Look at: http://www.motorola.com/Business/US-EN/Business+Product+and+Services/Bar+Code+Scanning
Barcode Reader Because im guessing my answer
There are numerous advantages to the use of a bar code. The primary two are speed and accuracy. A bar code reader can decipher the code in just thousandths of a second and transmit it with near perfect accuracy - much better than humans can.
Bar-code scanner & Credit/debit card reader.