Commodity coding refers to the process of identifying commodities with a set of Arabic numerals, which are called codes. Commodity code and commodity bar code are two different concepts. Commodity codes are digital information representing commodities, and commodity bar codes are symbols representing these information. In the work of commodity bar code, in order to make commodity bar code symbols, the commodity should be digitally coded first. The codes of commodity bar codes are compiled according to the uniform rules stipulated by EAN, and are divided into standard version and abbreviated version. Commodity barcodes have the following principles: 1. Uniqueness refers to the one-to-one correspondence between a commodity item and its identification code, that is, a commodity item has only one code, and a code only identifies the same commodity item. Once the commodity item code is determined, it will never change. Even if the production and supply of the commodity stop, the code shall not be allocated to other commodity items for a period of time (3 years in some countries). 2. Meaningless code means that the code number itself and its position do not represent any specific information of the commodity. In EAN and UPC systems, commodity coding is only a means to identify commodities, not a means to classify commodities. Meaningless makes commodity coding have the advantages of simplicity, flexibility, reliability, full use of code capacity and strong vitality. This coding method is especially suitable for larger commodity systems.