1D BARCODES (one-dimensional or linear)
for a relatively small number of characters (up to a maximum of 25 characters). If the number of characters is too large, the reader must be removed very far from the bar code when scanning, so that the scanner beam completely covers the barcode. If the distance is too large, the resolution of the scanner is no longer sufficient. 1D and 2D scanners can be used to read 1D codes.
- Code 128 Code 128 offers a great deal of information and is now replacing Code 39 more and more. All characters between ASCII 0 and ASCII 127 can be represented with a high information density. Shift characters at the beginning of the code or before a block (character set A, B and C) allow the use of the same symbols for several characters. E.g. In code 128 character set C, only the digits from 0 to 9 can be encoded. Because of this limitation, a barcode (module) always contains two digits, whereas normally only one character can be encoded. A purely numeric code 128 therefore requires considerably less space than an alphanumerically encoded code 128. If no other factors are involved, code 128 is the first choice for the new introduction of bar code technology.
- Code 39 is an older alphanumeric code, which in the standard version contains the characters A Z, digits 0 9 and the special characters $% / + .- and is easy to manufacture because of its large pressure tolerances. Start and stop signs are indicated by a *. Because of the start / stop characters, a code 39, which is used without a check digit, is not as uncertain as a code 2 of 5 interleaved without check digit, but a use of the check digit is recommended. The extended version of Code 39 allows the encoding of lowercase characters, but has a smaller information density.
- Code 93 is a further development of Code 39 and is more similar to Code128. With alphanumeric coding, code 93 reaches the highest level of linear barcodes, but has almost no meaning in Europe.
- Codabar provides a limited alphanumeric character set, originally developed for retail, but quickly replaced by EAN and Code128.
- Code 2 of 5 interleaved is a very compact bar code. However, the range of characters includes only the digits 0-9. However, it is an uncertain code, which requires an increased error rate, especially if this code is used without a check digit and without a length fixation. This code should therefore be used only if a barcode of a different type with the required number of characters can not be accommodated on a given small area.
2D BARCODES (one-dimensional)
are suitable for larger amounts of information (more than 25 characters). The information is encoded in the form of (white and black) dots in the area. A distinction is made between stacked codes, matrix codes, point codes and some other special forms. The term "two-dimensional barcode" should be avoided since the subword "bar" stands for the bars of the classic one-dimensional code. 2D codes, except for stacked barcodes such as the PDF417, do not contain bars. A 2D scanner is required to read 2D codes. The most common are stacked codes and matrix codes. If a 2D scanner is available, real matrix codes are the first choice.
- Codablock was developed between 1990 and 1994 in Germany as a stacked variant from the standard bar codes Code 39 and Code 128. Each line is indicated by a line number and contains a certain number of characters. Finally, a checksum follows.
- Code 49 is a stacked code with 3 error correction procedures and therefore meets increased security requirements against other identification procedures.
- The PDF417 ( "Portable Data File") can contain max. 2000 characters and provides 10 error correction levels. The ratio of data content to size is much worse compared to DataMatrix. PDF417 can also be read by laser scanners that can not detect matrix codes, but not particularly efficiently.
- The QR Code (Quick Response Code) is widely used. Many smartphones with built-in camera can read this code. There are 4 error correction stages. Up to 4000 alphanumeric characters can be encoded. Larger data sets can be divided into up to 16 individual codes. The Micro-QR code can hold up to 35 digits.
- DataMatrix is currently gaining in importance, e.g. As an electronic stamp and as a part marking in the aerospace industry and in medical technology.
- The MaxiCode was developed by UPS in 1989 to identify, track and sort packages. Unlike other 2D codes, it has a hexagonal structure.
- The Aztec Code is used by the german railway (Deutsche Bahn), the Austrian and Swiss Federal Railways for online and mobile tickets. The US government uses this code to store biometric data on entry and exit.