Bar codes have been around for a long time. Bar codes have originated from Morse code. Like the length of the tone determines the character, similarly in bar codes visual lines of varying thickness represent different characters and numbers. Not just lines they can be in circles, squares and triangles, hexagonal and any other shape that can be coded to be read by the scanner. The barcode scanner reads this bar code by the degree of absorption by the dark bands and the software analyzes the width of the line to give the corresponding character.
These have been extensively used in shopping markets, shipments, copy proofing, and other places where a large number of things need to be scanned rapidly. Bar codes have evolved from black and white lines to multicolored squares and triangles that cannot be read by a laser but a camera. From simple one dimensional bar codes to complex 2 dimensional barcodes have been introduced that can store more information.
Smart phones with high definition cameras are being infused with bar code reading functionality that gives real time info by just facing your phone camera towards this bar code. This is being used in magazines, televisions, newspapers and other places where a lot of information needs to be supplied. Companies such as Microsoft and Google have come out with operating system specific Bar codes readers, which can read out information from their specific bar codes.
Microsoft has a triangular multicolored barcode that requires sophisticated algorithms to decode. It has been used to connect digital content to printed content. The use of mobile phones as a credit card has led to the use of phones to pay for the item whose bar code is being analyzed. It is getting at a point where you do not have to give out any information at the place where you are going to get your merchandise, by just remotely paying and ending the transaction.