All barcode labels have are uniqueness. The same kind of specifications products should correspond to the same product codes. The same kind but different specifications product correspond to the different codes. According to the different nature of product, such as: weight, packing, specifications, smell, color，shape and so on. Barcode can give products the different commodity code.

Early barcode labels pattern is not what it is now, like miniature archery target, so at that time, barcode labels 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.They also having a high efficiency, reading a barcode by machine is very fast, which is equivalent to 40 characters per second, this greatly improves the efficiency of data management.

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.

As white object can reflect the various wavelengths of visible light, the black object can absorbs various wavelengths of various wavelengths, when the light source send out light, reflected on the barcode, the light incident into the barcode scanner’s photoelectric conversion device, and according the different strength of the reflected light signal, barcode can be converted into a corresponding electrical signal.

Barcode is flexible and practical. Barcode symbol can manually input by keyboard, can also use related equipment to build a recognition system to automated identification, and also can be linked to entire system to achieve the automated management.