UPC
(Unified Product Code) can only represent numbers. There are five versions: A, B, C, D, and E. Version A - 12 digits. Version E - 7 digits. The last digit is the check digit. The size is 1.5" wide and 1" high, and the background must be clear. It is mainly used in the United States and Canada, and is used in industry, medicine, warehouses and other sectors. When UPC is decoded as twelve digits, the definition is as follows: first digit = numerical identification (as established by the UCC (Uniform Code Committee)). Digits 2-6 = manufacturer's identification number (including the first digit). 7-11 = unique manufacturer product code 12th digit = check digit (used for error detection)
Code 3 of 9
Can represent letters, numbers and other symbols* **43 characters: A -Z, 0 - 9, -.$/+%, the length of the pace barcode is variable, usually "*" is used as the starting and ending character for the check code, and the code density is between 3 - 9.4 characters per inch, the blank area is 10 times that of the narrow strip, used in industry, books, and ticket automation management.
Code 128
Represents high-density data. The string length is variable and the symbol contains a check code. There are three different versions: A, B, and C. Each of them can use 128 characters. In the three string sets A, B, or C, they are used for industry, warehouse, retail and wholesale.
Interleaved
2-of-5 (I2 of 5) can only represent numbers 0-9, variable length, continuous barcode, all bars and spaces represent codes, first The first number starts with a bar, and the second number consists of an empty space. The blank area is 10 times wider than the narrow bar. It is used in commodity wholesale, warehouses, airports, production/packaging identification, and industry. The barcode reading rate is high and can be applied to fixed The scanner scans reliably and has the highest density of any 1D barcode.
Codabar
(Cudabar code) can represent numbers 0 - 9, characters $, +, -, and a, b which can only be used as start/terminator , c d four characters, variable length, no check digit, used in material management, libraries, blood stations and current airport parcel delivery, the blank area is 10 wider than the narrow bar, non-continuous barcode, each character represents It’s 4 bars and 3 empty. Codabar also known as NW 7, NW 7 is the name in Japan.
PDF417
(QR code)
A barcode composed of multiple lines does not need to be connected to a database and can store a large amount of data. It is used in: hospitals, Driver's license, material management, and cargo transportation. When the barcode is damaged to a certain extent, error correction can enable the barcode to be correctly decoded. PDF417 is a product developed by Symbol Technology Company in 1990. It is a multi-line, continuous, variable-length symbolic identifier that contains a large amount of data. Each barcode has 3-90 lines, and each line has a start part, data part, and end part. Its character set includes all 128 characters, and the maximum data content is 1850 characters.
1) Introduction to PDF417
The PDF417 code was invented by Dr. Wang Yinjing (sound), a Chinese in the United States. PDF is the abbreviation of the three words Portable Data File in English, which means "portable data file". Because each symbol character that makes up a barcode is composed of 4 bars and 4 spaces, if the narrowest bar or space that makes up the barcode is called a module, then the total number of modules of the above 4 bars and 4 spaces is one. It is set as 17, so it is called 417 code or PDF417 code.
2) Characteristics of PDF417
1. Large information capacity: In addition to letters, numbers, and ASCII characters, the PDF417 code can also express binary numbers.
In order to make the encoding more compact and increase the information density, PDF417 has three formats when encoding:
* Extended alphanumeric compression format can accommodate 1850 characters;
* Binary/ASCII format Can hold 1108 bytes;
* Number compressed format can hold 2710 numbers.
2. Error correction capability
One-dimensional barcodes usually have a verification function to prevent misreading. Once the barcode is defaced, it will be rejected. The two-dimensional barcode can not only prevent errors, but also correct them. Even if the barcode is partially damaged, the correct information can be restored.
3. The printing requirements are not high
Ordinary printing equipment can print, and faxes can also be read.
4． Can be read with a variety of reading devices
PDF417 codes can be read with laser readers with rasters, linear and area scanning image readers.
5. The size is adjustable to adapt to different printing spaces
6. The disclosure of code system has formed an international standard, and China has also formulated a national standard of 417 codes.
3) Error correction function of PDF417
The error correction function of 2D barcode is achieved by repeatedly representing part of the information (redundancy). For example, in the PDF417 code, in addition to the information of this line, a certain line also contains information that reflects characters (error correction codes) in other positions. In this way, even if part of the barcode is damaged, its information can be restored through the error correction code that exists elsewhere.
The error correction ability of PDF417 is divided into 0~8***9 levels according to the number of error correction code words. See Figure 4. The higher the level, the more correction code words and the stronger the correction ability. Barcode Also bigger. When the correction level is 8, the barcode can be read correctly even if it is 50% stained.
4) Several deformations of PDF417
PDF417 also has several deformed coding forms:
* PDF417 truncation code
In relatively "clean" environments where the likelihood of barcode damage is small, the line indicator on the right can be omitted and the terminators reduced.
* PDF417 microcode
Further reduced PDF code.
* Macro PDF417 code
When the file content is too long to be represented by one PDF417 code, a macro PDF417 code containing multiple (1~99999) barcode blocks can be used. express.
Take PDF417 code as an example to introduce the features and characteristics of two-dimensional barcodes.
Advantages of two-dimensional barcodes
As can be seen from the above introduction, two-dimensional barcodes have obvious advantages compared with one-dimensional barcodes, which can be summarized in the following aspects:
1) Larger data capacity
2) Beyond the limitations of alphanumeric characters
3) The relative size of barcodes is small
4) Resistant to damage
Composite barcode
This is a new type of code system that consists of two barcode symbols that are very close to each other and contains interrelated data. Usually one of them is a linear symbol and the other is a stacked or array symbol.
It should be used when different information is required at different points in the life cycle of the target object, or when space is limited.
At present, its mainstream application is UCC.EAN composite barcode, which mainly meets applications such as the pharmaceutical industry that need to contain product identification and additional information (such as batch number, expiration date). These symbols consist of a standard one-dimensional code of the UCC.EAN system class (such as EAN-13 or UPC-A or UCC.EAN 128) and a two-dimensional stacked code.
Since the International Article Numbering Association (EAN) promulgated a new composite code standard in 1999, EAN and the UCC (Uniform Code Committee) have jointly established four composite code application research groups to study Specific technologies and application pilot issues for applying composite codes in commercial and logistics systems. In August 1999, EAN and UCC jointly announced the joint development of application standards for composite codes in supply chain management, and planned to publish the first batch of application standards in January 2000.
These standards will include application standards for composite codes on bulk (randomly weighed) items, non-retail food, medical and health supplies and electronic components, as well as application standards for logistics management barcodes. As a new coding system, the composite code maintains the integrity and compatibility of the international article coding system.
Bar code is by far the most economical and practical automatic identification technology. Barcode technology has the following advantages
A. Fast input speed: Compared with keyboard input, barcode input is 5 times faster and can achieve "instant data input".
B． High reliability: the error rate of keyboard input data is one in three hundred, the error rate of using optical character recognition technology is one in ten thousand, and the error rate of using bar code technology is less than one in a million.
C. Large amount of information collected: Traditional one-dimensional barcodes can collect information of dozens of characters at a time, while two-dimensional barcodes can carry information of thousands of characters and have certain automatic error correction capabilities.
D. Flexible and practical: Barcode identification can be used alone as a means of identification, or it can be formed into a system with related identification equipment to achieve automatic identification, and it can also be connected with other control equipment to achieve automated management.
In addition, barcode labels are easy to produce and have no special requirements for equipment and materials. The identification equipment is easy to operate and does not require special training, and the equipment is relatively cheap.
E. The cost is very low. In the retail industry, because barcodes are printed on product packaging, the cost is almost zero.