Barcode is constitute by plurality of black bars and blank, the width of black bars are different, and these bars arranged in encoding rules for expression a group of information, graphics and identifier. It usually appear in our lives asbarcode labels.

The barcode labels are having a high reliability. The accuracy of reading a barcode is far more than manual records, 15000 characters just appear one error. Barcode has greater flexibility, the identification device and the relative position of the labels’ strip has the degree of freedom is much greater than the OCR( Optical Character Recognition). A barcode usually expression the information only by one-dimensional, on the same barcode, the information represented is continuous and the same, so even if the label has some shortcomings, you can still enter the correct information from the normal part.

May be barcode labels seems very simple just like many black lines printed on a paper, but the recognition principle of barcode is not simple. The barcode need to be complied according to certain rules so that can be change into meaningful information. In order to get the information, it is need two steeps, scanning and decoding.

Early barcode pattern is not what it is now, like miniature archery target, so at that time, called "bulls eye" code. Target’s concentric circles are plotted by the circular bar and empty circular. In principle the "bulls eye" code is very similar with later barcode, process and commodity economy is not yet capable of printing out this code.

10 years later, Joe Woodland a IBM's engineers, became the founder of the North American Uniform UPC code. Later Gilad Feiyiseer (Girard Fessel) is represented by several inventors in 1959 drew a patent describes the numbers 0-9 in each number composed by the seven-segment parallel bars. But this code is difficult to read by machine. However, this vision is indeed promoted barcode labels generation later development, soon E • F • Brinker (E • F • B rinker) applied for another patent, the patent barcode identification on the tram. The 1960s Sylvester Wo Niya(Sylvania) invention of a system, adopted by the North American rail system. These two can be said that the early application of barcode technology.