Codabar

Codabar is a linear barcode symbology developed in 1972 by Pitney Bowes Corp. ([1]). 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

Although Codabar has not been registered for US federal trademark status, its hyphenated variant Code-a-bar is a registered trademark^[1].

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 the creation of 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^[2].

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^[3].

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^[4].

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 comprises 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 0.0065 inches, allowing 11 characters per inch to be encoded. Logical 0s and 1s are represented by narrow and wide elements respectively^[5].

Char.	Pattern	Bars	Spaces
0	lll l	0001	001
1	lll l	0010	001
2	ll ll	0001	010
3	l lll	1000	100
4	lll l	0100	001
5	lll l	1000	001
6	l lll	0001	100
7	l lll	0010	100
8	l lll	0100	100
9	ll ll	1000	010
-	ll ll	0010	010
$	ll ll	0100	010
:	llll	1011	000
/	llll	1101	000
.	llll	1110	000
+	llll	0111	000
A or T	ll l l	0100	011
B or N	l l ll	0001	110
C or *	ll l l	0001	011
D or E	ll l l	0010	011

References

1. ^ http://uspto.gov
2. ^ http://mdn.morovia.com/manuals/bax3/shared.bartech.php#Symbology.Codabar
3. ^ http://www.makebarcode.com/specs/codabar.html
4. ^ http://aimglobal.org/aimstore/linearsymbologies.asp (Dead Link)
5. ^ http://www.barcodeman.com/info/codabar.php

External links

• EAN MediaWiki extension, a MediaWiki extension, visualizing Codabar/Code39/EAN-13/EAN-8/UPC-A barcodes by specifying only the numbers/symbols in the wiki-text.
• Free Online Codabar generator.