1, according to the code system classification
1) UPC code
In 1973, the United States took the lead in the domestic commercial system in the application of the UPC code after the Canada also in the commercial system to adopt the UPC code. the UPC code is a length of a fixed length of the continuous numerical code system, the character set for the number 0 ~ 9. it uses four element widths Each bar or space is 1, 2, 3 or 4 times the width of the unit element.There are two types of IPC codes, UPC-A code and UPC-E code.
2) EAN code
In 1977, the European economic ****syndicate countries in accordance with the standard of UPC code to develop the European article code EAN code, compatible with UPC code, and both have the same symbol system.EAN code character numbering structure is the same as the UPC code, is also the length of the fixed, continuous type of numerical code system, and its character set is the number of digits 0 ~ 9. It uses four element widths, each bar or space is 1, 2, 3 or 4 times the width of the unit element.There are two types of EAN code, namely EAN-13 code and EAN-8 code.
3) Cross 25 code
Cross 25 code is a variable length continuous self-checking digital code system, its character set for the number 0 ~ 9. Using two element widths, each bar and empty is wide or narrow elements. The number of encoded characters is even, all the data in odd positions are encoded in bars, and the data in even positions are encoded in blanks. If coded for an odd number of data, a zero is prepended to the data to make the data an even number of digits.
4) 39 code
39 code is the first alphanumeric code system. 1974 by Intermec introduced. It is a discrete self-correcting alphanumeric code system with comparable length. Its character set for the number 0-9, 26 uppercase letters and 7 special characters (-,. , Space, /, %, ￥), **** 43 characters. Each character consists of 9 elements with 5 bars (2 wide bars, 3 narrow bars) and 4 blanks (1 wide blank, 3 narrow blanks), which is a discrete code.
5) Kudelbar code
Kudelbar code (Code Bar) appeared in 1972, is a variable length continuous self-checking digital code system. Its character set for the number 0-9 and six special characters (-,:, /,. , +, ￥), *** 16 characters. Commonly used in warehouses, blood banks and air courier packages.
6) 128 code
128 code appeared in 1981, is a variable length continuous type self-checking digital code system. It uses four element widths, each character consists of three bars and three blanks, *** 11 cell element width, also known as (11, 3) code. It consists of 106 different, the same bar code characters, each bar code character has three different meanings of the character set, respectively, A, B, C. It uses these three alternate character sets to encode 128 ASCII codes.
7) 93 code
93 code is a variable length continuous alphanumeric code system. Its character set becomes the numbers. 0-9, 26 uppercase letters and 7 special characters (-,. , Space, /, +, %, ￥) and 4 control characters. Each character consists of 3 bars and 3 hans, ***9 element width.
8) 49 code
49 code is a multi-line continuous type, variable length alphanumeric code system. Appeared in 1987, it is mainly used for symbols on small item labels. Multiple element widths are used. Its character set is the numbers 0-9, 26 uppercase letters and 7 special characters (-,. , Space, %, /, +, %, ￥), 3 function keys (F1, 陀, F3) and 3 transformation characters, ***49 characters.
9) Other code systems
In addition to the above code, there are other code systems, such as 25 code appeared in 1977, mainly used for electronic component labels; matrix 25 code is a deformation of the 11 code; Nixdorf code has been replaced by the EAN code Plessey code appeared in May 1971 is mainly used in libraries and so on.
2, according to the number of dimensions classification
1) ordinary one-dimensional bar code
Ordinary one-dimensional bar code since the introduction of the present, quickly gained popularity and widely used. However, because the information capacity of one-dimensional bar code is very small, such as commodities on the bar code can only accommodate 13 Arabic numerals, more information describing the commodity can only rely on the support of the database, leaving the pre-established database, the bar code has become a source of water, no wood, and thus the scope of application of the bar code is subject to certain limitations.
2) Two-dimensional barcode
In addition to the advantages of ordinary barcode, two-dimensional barcode also has the advantages of large information capacity, high reliability, strong confidentiality and anti-counterfeiting, easy to produce, low cost and so on. <BR> U.S. Symbol officially launched in 1991 named PDF417 two-dimensional bar code, referred to as PDF417 bar code, that is, "Portable Data File". FDF417 bar code is a high-density, high-information content of the Portable Data File is to realize the documents and cards, etc., large-capacity, high-reliability information. FDF417 barcode is a high-density, high-information content of portable data files, is the realization of documents and cards, such as large-capacity, high-reliability information automatically stored, carried and available for automatic machine-readable ideal means.
3) multi-dimensional bar code
Into the 1980s, people around how to improve the information density of bar code symbols, research work. Multi-dimensional bar code and container bar code has become the direction of research, exhibition and application. <BR> Information density is an important parameter to describe the bar code symbol according to, that is, the number of letters may be written in the unit length, usually recorded as: the number of letters/cm. the main factors affecting the information density is the bar, empty structure and the width of the narrow element system. <BR> 128 and 93 codes are the successful attempts to increase the density. 128 code city was recommended for application in 1981; while 93 code was put into use in 1982. Both codes have a symbol density nearly 30% higher than that of 39 codes. <BR> With the development of bar code technology and bar code three system of the kinds of increasing, bar code standardization appears more and more important. To this end, has developed a military standard 1189; cross 25 codes, 39 codes and Coda Bar code ANSI standard MH10.8M and so on. At the same time, some industries have also begun to establish industry standards to meet the needs of development. Since then, David Allier has developed the 49 code. This is a non-traditional barcode symbol, which has a higher density than the previous barcode symbols. Ted Williams GFI988 introduced the 16K code, which is similar in structure to the 49 code and is a relatively new code system for laser systems.