Codabar is a linear barcode symbology developed in 1972 by Pitney Bowes Corp. (http://other.lookstrike.com/barcode/demo/html/codabar.php). It is also known as Codeabar, Ames Code, NW-7, Monarch, Code 2 of 7, Rationalized Codabar, ANSI/AIM BC3-1995 or USD-4.

Library Book Barcode

It was designed to be accurately read even when printed on dot-matrix printers for multi-part forms such as FedEx airbills and blood bank forms, where variants are still in use as of 2007. Although newer symbologies hold more information in a smaller space, Codabar has a large installed base in libraries. It is even possible to print Codabar codes using typewriter-like impact printers, which allows to create a large number of codes with subsequent numbers without having to use any digital equipment. After each printed code, the printer's stamp is mechanically turned to the next number, as for example in mechanical mile counters.

Check Digit

Because Codabar is self-checking, most standards do not define a check digit.

The variants of Codabar in commercial and public use will sometimes define a proprietary check digit.

For instance in an all-numeric string, the check digit algorithm might double the odd digits, take modulo 9, sum the results with the even digits, and represent the total in modulo 10. (http://www.makebarcode.com/specs/codabar.html)

Encoding

Depending on the particular specification, for example the Association for Automatic Identification and Mobility's Uniform Symbol Specification, the body of a Codabar string may only encode the numerals 0 through 9. Some variants allow the symbols dollar, dash, plus sign, colon, slash, and dot. (http://aimglobal.org/aimstore/linearsymbologies.asp)

The alphabet characters A, B, C, D, and in some specifications, E, N, asterisk, and T are used in matching pairs to mark the beginning and end of the barcode. They do not appear in the body of a Codabar string.

Each character is comprised of 7 binary identifiers (4 bars and 3 spaces). Each identifier or element is made up of a certain multiple of constant-width modules. Different specifications allow for different width modules, the smallest being 0.065 inches, allowing 11 characters per inch to be encoded. Logical 0s and 1s are represented by narrow and wide elements respectively. (http://www.barcodeman.com/info/codabar.php)

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