Commodity bar codes are composed of a group of black and white or color stripes with different thicknesses, which are used to represent commodity codes. It consists of bar code symbols, character codes and blank areas. 1. Overview of barcode. Bar code was first put forward by N.T.Woodland of America in 1949. In recent years, with the popularization of computer application, the application of bar code has been greatly developed. Barcode can indicate the country of production, manufacturer, product name, date of production, book classification number, starting and ending place, category and date of mail, so it has been widely used in many fields such as commodity circulation, book management, post and telecommunications management, banking system and so on. Barcodes are composed of bars and spaces with different widths and reflectivity according to certain coding rules (coding system). A graphic identifier used to represent a set of numeric or alphabetic information. That is, bar code is a set of parallel lines with different thicknesses, and the spacing is arranged according to certain rules. Common bar codes are composed of black bars (referred to as bars) and white bars (referred to as spaces) with great differences in reflectivity. It consists of barcode scanner, amplification and shaping circuit, decoding interface circuit and computer system. 3. The principle of barcode scanner recognizing barcodes. Because objects with different colors reflect different wavelengths of visible light, white objects can reflect various wavelengths of visible light, while black objects absorb various wavelengths of visible light. Therefore, when the light emitted by the light source of barcode scanner shines on black and white barcodes through the diaphragm and the convex lens 1, the reflected light is focused by the convex lens 2 and irradiated on the photoelectric converter in barcode scanner, so the photoelectric converter receives reflected light signals with different intensities corresponding to white bars and black bars and converts them into them. The widths of white bars and black bars are different, and the duration of corresponding electrical signals is also different. However, the electrical signals corresponding to the bars and spaces of bar codes output by photoelectric converters are generally only about 10mV. Can not be used directly, the electrical signal output by photoelectric converter should be sent to amplifier for amplification. The amplified electrical signal is still analog. In order to avoid false signals caused by defects and stains in bar codes, a shaping circuit should be added after the amplification circuit to convert analog signals into digital electrical signals so that the computer system can accurately interpret it. The pulse digital signal of the shaping circuit is converted into digital and character information by the decoder. It can identify the coding system and scanning direction of bar code symbols by identifying the start and end characters. The number of stripes and spaces can be determined by measuring the number of pulse digital electrical signals 0 and 1, and the width of stripes and spaces can be determined by measuring the duration of signals 0 and 1. In this way, the number of bar code symbols, the number of spaces, the corresponding width and the code system used can be obtained. According to the coding rules corresponding to the coding system, barcode scanner can convert bar code symbols into corresponding digital and text information, and send them to the computer system for data processing and management through the interface circuit. Completed the whole process of bar code reading. EAN- 13 general commodity bar code generally consists of prefix, manufacturer code, commodity code and check code. The prefix code in commodity bar code is used to identify the country or region, and the code is given in ean international. For example, 00-09 stands for the United States and Canada. 45-49 stands for Japan. 690-692 stands for Chinese mainland, 47 1 stands for Taiwan Province Province and 489 stands for Hong Kong Special Administrative Region. The empowerment of manufacturers' codes is organized by article codes in various countries or regions, while in China, the National Article Coding Center gives manufacturers' codes. Commodity codes are codes used to identify commodities, and the right to assign codes is exercised by the product manufacturers themselves. Manufacturers themselves decide which Arabic numerals to use for their products according to the prescribed conditions. At last, the 1 parity code is used to check the correctness of the L- 12 digital code from the left in the barcode. Full text: Commodity barcode refers to a sign composed of a group of regularly arranged bars, spaces and their corresponding characters, which is used to express certain commodity information. Among them, the bar is dark and empty, which is a reading device used to scan and read bar codes. Its corresponding characters consist of a group of Arabic numerals for people to read directly or input data to the computer through the keyboard. This set of spaces and corresponding characters represent the same information. Bar code technology was born with the development and application of computer and information technology. It is a new technology integrating coding, printing, identification, data acquisition and processing. Using bar code scanning is the general trend of future market circulation. In order to make goods circulate freely and widely in the world, enterprises must abide by the relevant provisions of commodity bar codes whether designing, manufacturing, applying for registration or using commodity bar codes. At present, ENA barcode, UPC barcode, 25 barcode, cross barcode, Kudba barcode, Sanjiu barcode and 128 barcode are commonly used in the world, among which EAN barcode is the most commonly used commodity. EAN commodity bar code, also known as general commodity bar code, is formulated by ean international and is widely used in the world. It is the most widely used commodity bar code in the world. At present, this commodity bar code is being used in China. EAN commodity bar codes are divided into EAN- 13 (standard version) and EAN-8 (abbreviated version). EAN- 13 general commodity bar code generally consists of prefix, manufacturer code, commodity code and check code. The prefix code in commodity bar code is used to identify the country or region, and the code is given in ean international. For example, 00-09 stands for the United States and Canada. 45-49 stands for Japan. 690-692 stands for Chinese mainland, 47 1 stands for Taiwan Province Province and 489 stands for Hong Kong Special Administrative Region. The empowerment of manufacturers' codes is organized by article codes in various countries or regions, while in China, the National Article Coding Center gives manufacturers' codes. Commodity codes are codes used to identify commodities, and the right to assign codes is exercised by the product manufacturers themselves. Manufacturers themselves decide which Arabic numerals to use for their products according to the prescribed conditions. At last, the 1 parity code is used to check the correctness of the L- 12 digital code from the left in the barcode. The coding of commodity bar codes follows the principle of uniqueness, so as to ensure that commodity bar codes will not be repeated in the global scope, that is, a commodity item can only have one code, or a code can only identify one commodity item. Commodities with different specifications, different packages, different varieties, different prices and different colors can only use different commodity codes. The standard size of commodity bar code is 37.29mmx26.26mm, and the magnification is 0.8-2.0. When the printing area allows, the barcode with magnification of 1.0 should be selected to meet the reading requirements. The smaller the magnification, the higher the printing accuracy. When the printing accuracy can not meet the requirements, it is easy to read the bar code. Because the identification of bar code is realized by the color contrast between bar code and blank bar code, generally speaking, as long as the color can meet the requirements of contrast (PCS value), light color can be used as blank color, such as white, orange and yellow, and dark color as bar, such as black, dark green and dark brown. The best color scheme is black stripes and white spaces. According to the practical experience of bar code detection, red, gold and light yellow should not be used as bar code colors, and transparent and gold should not be used as blank colors. EAN-8 commodity bar code refers to the 8-digit commodity bar code used for identification, which consists of 7-digit commodity item code and 1 digit check code. The birth of commodity bar code greatly facilitates the circulation of commodities, and modern society cannot do without commodity bar code. According to statistics, at present, there are 500,000 kinds of products in China that use the international commodity bar code. After China's entry into the WTO, enterprises will surely win more space for activities on the international stage. To keep up with international practice and meet the needs of international trade, enterprises should not mistreat commodity bar codes. The barcode prefix code of EAM members in the United States and Canada 00-09 Israel 729 Denmark 57 (in-store code) 20-29 Venezuela 759 Norway 70 Japan 45-49 Uruguay 773 Switzerland 76 Belgium/Luxembourg 54 Bolivia 773 Spain 84 Finland 64 Chile 780 Austria 90-9 1 Sweden 73 Ecuador 786 New Zealand 94 Italy 80-83 Cuba 850 Slovenia 383 Netherlands 87 Czech 859 Germany Malaysia 893 Sri Lanka 479 Russia 460-469 Vietnam 977 Hong Kong 489 Estonia 474 Mexico 750 Cyprus 529 Lithuania 477 Colombia 770 Malta 535 Philippines 480 Peru 775 Portugal 560 Greece 520 Argentina 779 Poland 590 Macedonia 53 1 Paraguay 780. S 609 Iceland 569 Slovakia 858 Albania 6 13 Romania 594 Yugoslavia 860 Chinese mainland 690-692 South Africa 600-60 1 Thailand 885 France 30-37 Morocco 61India 890 Britain 50 Turkey 6 19.