Barcode
A barcode is an optical machine-readable representation of data, which shows certain data on certain products.linear or 1D barcodes comes as the parallel lines. There are also squares, dots, hexagons and other geometric patterns within images termed 2D . barcode readers are used to read the barcode. Barcodes”especially the UPC”have slowly become an essential part of every product. some examples of its use are:
-grocery store, department store, and mass merchandiser
- shop floor control applications
-On patient identification wrist bands
-Document Management tools etc.

Symbologies
The mapping between messages and barcodes is called a symbology. The different technical specifications in a symbology is:
-encoding of the single digits/characters into bars and space
-start and stop markers into bars and space,
-computation of a checksum.

UPC bar codes
UPC(Universal Product Code) bar codes were originally created to help grocery stores. The last digit of the UPC code is called a check digit which helps the scanner determine if it scanned the right number. It is done through a specific algorithm. If the check digit it calculates is different from the check digit it reads, then the code is rescanned.

advantages of barcode
-Fast-selling items can be identified quickly
-Slow-selling items can be identified thus preventing a build up of unwanted stock.
-Items may be repriced on the shelf
-a Unique Identifying Number (UID) can be assigned by the manufacturer to every packet
-A relational database can be created to relate the UID to information such as order number, items packed, qty etc


for more details, refer these links:
http://en.wikipediawiki/Barcode
http://electronics.howstuffworksgadgets/...ts/upc.htm

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