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Related terms
Barcode characters: a number of bars and a space.
Article: bar code in the low reflectivity of the light part, usually black.
Empty: The portion of the bar code that has a high reflectance to light, usually white.
Blank area: To ensure the normal bar code reading and bar code at both ends to retain the same color with the empty area
Start character: In the bar code starting position, that a special bar code bar code characters.
Terminator: At the end of the bar code, a special bar code character indicating the end of the bar code.
Parity: A bar code character used to verify the accuracy of a barcode. It is generated according to a certain rule of character according to the character information represented by the barcode, usually before the terminator.
Unit: Bar code symbol in the same width of a color range. A unit consists of one or more modules. Module: The basic unit of the bar code.

Three nine yards
Is a bar code introduced by Intermec in 1975. It can represent numbers, English letters and "-", ".", "/", "+", "%", "$", "" ( Space) and "*" are 44 symbols, where "*" is used only as an initiator and a terminator.
Three nine codes and a simple coding rules, low bit error rate, can represent the number of characters and so on, so in various fields has a very wide range of applications. China has also developed a corresponding national standard (GB12908-91).
There are only two types of cell widths - wide and narrow. Wide unit This is a narrow unit of 1 to 3 times the general multi-choice 2 times, 2.5 times or 3 times. Three nine yards of each bar code character consists of nine units, of which there are three wide units, the rest is a narrow unit, so called three nine yards.

Commodity bar code (EAN, UPC code)
Business is the first application of bar code technology in the field. In commercial automation systems, the bar code is the key commodity.
In the national standard GB / T 12904, a barcode for commodity is defined as a modular combination of bar codes used to identify internationally accepted commodity codes.
In 1970 the United States Supermarket Committee developed the Universal Commodity Code UPC code, the United States Uniform Code Committee (UCC) and in 1973 established the UPC bar code system, and the full realization of the code system standardization. UPC bar code successfully applied in the field of commercial circulation, the bar code application and popularization has played a great role in promoting.
The successful use of UPC codes has led to the creation of the European Encoding System (EAN). To 1981, EAN has developed into an international organization, and EAN code and UPC code compatible.
The EAN / UPC code, as a consumer unit code, is used to uniquely identify a commodity on a global scale.
There are two versions of EAN - Standard and Short. Standard Edition that 13-bit number, also known as EAN13 code, shortened version of that 8-digit, also known as EAN8. The last bit of both barcodes is the parity bit, which is calculated from the previous 12 or 7 digits. Two versions of the encoding can refer to GB GB-12094-1998.
EAN code consists of prefix code, vendor identification code, commodity item code and check code. Prefix code is the international EAN organization logo members of the organization code, China is 690,691 and 692; manufacturer code is EAN coding organization in the EAN assigned prefix code based on the code assigned to the manufacturer; commodity item code from the manufacturer to code; Check Code In order to verify the correctness of the code. In the preparation of commodity item code, manufacturers must abide by the basic principles of commodity codes: the same commodity items must be the preparation of the same commodity item code; for different commodity items must be prepared for different commodity item code. To ensure that commodity items and their identification code one to one correspondence, that is, a commodity project only one code, a code only identifies a commodity item. Such as the sound of Jianlibao beverage bar code for the 6901010101098, of which 690 on behalf of China's EAN organization, 1010 on behalf of Guangdong Jianlibao company, 10109 is the canned drinks commodity code. This encoding to ensure that no matter when and where, 6901010101098 on the only species of goods.
In addition, books and journals as a special commodity also uses the EAN13 that ISBN and ISSN. Prefix 977 is used for ISSN ISSN, book number ISBN with 978 for the prefix, the country is assigned to use the beginning of the ISBN number 7, so our publishers published books on the bar code all 9787 at the beginning.

CODE 93 code
Code 93 has the same character set as Code 39, but its density is higher than 39, so in the case of insufficient area, you can use 93 yards instead of 39 yards.
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CODEBAR code
CodeBar is a widely used bar code in the field of medicine and books. Its character set is from 0 to 910 digits, "ABCD" four letters and "$ -: /.+" six special characters, among them "ABCD" only As an initiator and terminator, and can be any combination.

CODE 128 yards
Code 128 code can be represented from ASCII 0 to ASCII 127 a total of 128 characters, so that 128 yards. Code 128 and Code 39
Code has a lot of similarity, are widely used in enterprise internal management, production processes, logistics control system. The difference is that Code 128 can represent more characters than Code 39, with a higher density per unit length. Code 128 can be selected when the unit length can not be used to encode or encode characters beyond Code 39 limits. So Code 128 is more spiritual than Code 39.

MATRIX 25 code
Matrix 25 codes can only represent numbers 0 to 9.

INTERLEAVED 25 yd
Interleaved 25 code is a kind of bar and empty information that bar code, interleaved 25 code has two unit width, each bar code character consists of five units, of which two wide units, three narrow units. In an interleaved 25-yard symbol, the number of characters that make up the bar code symbol is even. When the number of characters is an odd number, the complement of 0 should be made even to the left. Bar code characters from left to right, with odd-numbered position of the characters, even-bit characters with empty said.
The interleaved 25-character set consists of the digits 0 to 9.

PDF417 two-dimensional bar code
(The PDF417 bar code contains the following red text content, error correction level 3)
One-dimensional bar code indicates the amount of data is limited, and does not have the error correction function, and two-dimensional bar code to make up for this deficiency. Two-dimensional bar code has just developed in recent years, is being applied to a variety of areas. One of the small blocks of lithography we see on the Pentium processor housing is the Data Matrix 2D Barcode.
PDF417 two-dimensional bar code is a stacked two-dimensional bar code, is currently the most widely used. PDF417 bar code is invented by the US company SYMBOL, PDF (Portable Data File) means "portable data files." Each bar code composed of bar code by the four and four empty 17 modules, it is called PDF417 bar code.
PDF417 bar code can represent digital, alphabetic or binary data, also can express Chinese character. A PDF417 bar code can hold up to 1850 characters or 1108 bytes of binary data, if only that number can accommodate 2710 numbers. PDF417 of the error correction capability is divided into 9, the higher the level, the stronger the ability to correct. Because of this error correction function, so that the defaced 417 bar code can also be read correctly. China has developed a national standard of PDF417 code.
PDF417 bar code need to have 417 decoding function of the bar code reader to identify, the current reader has thousands of yuan of products.
PDF417 bar code biggest advantage lies in its huge data capacity and strong error correction capability.

QR code Two-dimensional bar code
(The bar code contains the following red text content, error correction level M)
QR code is developed by Denso Corporation in September 1994, a matrix of two-dimensional code symbol, which in addition to a one-dimensional bar code and other two-dimensional bar code with the information capacity, high reliability, can represent Chinese characters and graphs Such as a variety of text information, security, security and other advantages, but also has the following main features:

* Each symbol represents 100 characters of information.

Ultra-high-speed reading:
QR Code from the English name of the Quick Response Code can be seen that the characteristics of ultra-high-speed reading QR Code code is different from the four 17 bar code, Data Matrix and other two-dimensional code of the main features. As the QR code is read by the CCD, the information in the entire QR code symbol is read by the position detection pattern of the QR code symbol and is realized by hardware. Therefore, the information reading process takes a short time, With ultra-high-speed reading characteristics. With the CCD two-dimensional bar code reading device, 30 characters of QR code symbols can be read every second, and only three symbols can be read for the four 17-bar code symbols with the same data information. Martix matrix code, can only read 2 to 3 symbols per second. QR Code code features ultra-fast reading is that it can be widely used in industrial automation production line management and other fields.

All-round reading:
QR Code has a full range of (360 °) reading characteristics, which is QR Code code is better than row row type two-dimensional bar code, such as the four one seven bar code another main feature, because the four one seven bar code is one-dimensional bar code symbol Row height of the truncation to achieve, therefore, it is difficult to achieve a full range of reading, the reading azimuth is only ± 10 °.
Can effectively represent Chinese characters, Japanese characters:
As the QR code with a specific data compression mode that Chinese characters and Japanese characters, it can only use 13bit to represent a Chinese character, and four one seven bar code, Data Martix and other two-dimensional code does not have a specific Chinese character representation mode, so only byte The 16-bit (2-byte) character is used to represent a Chinese character. Therefore, the QR Code is 20% more efficient than other two-dimensional barcodes in representing Chinese characters.

Encoded character set:
1, the number of digital data (0 to 9);
2, alphanumeric data (numbers 0-9; uppercase letters A to Z; 9 other characters: space, $,%, *, +, -,., /, :);
3, 8-bit byte data;
4, Japanese characters;
5, Chinese characters (GB 2312 corresponding to the Chinese characters and non-Chinese characters).

QR Code The basic characteristics of code symbols

QR Code can efficiently represent Chinese characters, the same content, the size is less than the same density PDF417 bar code. Currently most of the bar code printers on the market support QR code bar code, the proprietary Chinese character model is more suitable for our application. Therefore, QR code in China has a good prospect.