Codabar

Codabar is a self-checking symbology used primarily by libraries, blood banks, and photo labs. It is a discrete, variable-length, non-weighted barcode capable of encoding up to 16 different characters, along with 4 start/stop characters. These start/stop characters are typically the letters A, B, C, and D, although some implementations may use E, *, $, or +.

Codabar is a relatively old barcode symbology, developed in 1972 by Pitney Bowes. It is characterized by its wide inter-character gap and the use of only four different bar widths. This simplicity contributes to its relatively high read reliability, even with damaged or poorly printed barcodes.

While newer and more efficient barcode symbologies like Code 128 and Code 39 are available, Codabar remains in use due to its historical presence and the robustness of existing systems that utilize it. The symbology's ease of printing and reading has contributed to its longevity in specific applications.

Because Codabar is a discrete symbology, each character is independent of the characters adjacent to it. This characteristic simplifies decoding algorithms and makes it more tolerant of minor printing imperfections. The variable length nature of Codabar allows it to efficiently encode strings of various lengths.