2D Barcode
Linear Barcode
Codabar is a self-checking and binary level linear barcode symbology with no checksum digit appended. It is also known as Codeabar, Ames Code, NW-7 (means Narrow and Wide), Monarch, Code 2 of 7, Rationalized Codabar, ANSI/AIM BC3-1995 or USD-4. Codabar was designed by Pitney Bowes, Inc in 1972. It was originally used in retail system for labeling before the National Retail Merchants Association (NRMA) chose another barcode as standard. Codabar is widely used in libraries, package delivery system and photo labs. binary level barcodes. Codabar could be accurately read even when printed on dot-matrix printers for multi-part forms.
Structure of Codabar
Each group of 7 binary identifiers represents one character of Codabar. 2 or 3 of the 7 elements will be wide ones and the rest of them will be narrow.

Codabar may have many start and stop characters. It starts with one of four possible start characters a, b, c, or d (should be lower case letters).

A narrow, inter-character space which used to separtaes each character. Usually width of the inter-character space is equal to the width of the narrow space.

The data of the message with a narrow inter-character space between each character.
One of four possible stop characters a, b, c, or d (should be lower case letters).
Encoding Data of Codabar
Character set of Codabar contains of the 16 letters plus an additional 4 start/stop characters with variable length. The character density is about 5 chars each centimeter. The character set including:
  • Ten numeric digits from 0 to 9
  • Sixt special symbols: arithmetic operations (+-*/), colon (:), dollar symbol ($)
  • Four letters a, b, c and d.
  • In some specifications, E, N, asterisk, and T are used in matching pairs in start and stop characters.
Size of Codebar
Since many combination may emplyed of 7 binary identifiers, Codabar does not have fixed width of wide and narrow elements. Usually the highest module resolution printed on Codabar is 0.0065 in.(0.17mm). The information density at this module resolution level is 11 characters per inch. Symbol magnification in 25% increments is recommeneded when information density is lower. For example, information density of 9 characters per inch is recommeneded of module resolution of 0.0081 in.(0.21mm).
Checksum Digit of Codabar
Codabar is a discrete, self-checking symbology. Based on Codabar standard, checksum digit is not required. Implementer could still adopt the checksum digit to raise the level of digits security. Many libraries employs the method which totally 14 digits. Including 13 digits plus a checksum digit. For example:
  • Type of digits is represented by digit 1.
  • Institution is represented by 2 to 5 digits followed.
  • Individual patron or item is represented by 6 digits followed.
  • The last Digit 14 is the checksum digit.