Check digit: none
Use: General purpose / Medical/ Shipping and distribution / Transportation
(used by U.S. blood banks, photo labs, and on FedEx airbills)
Length: Variable length (any length)
Supported characters: 0 - 9, '-', '$', ':', '/', '.', '+'
Class: Alphanumeric Symbology
Special notes: Encoded message (string) must start and end with one of the start/stop characters ('A', 'B', 'C', D')

Codabar is a discrete, self-checking symbology that may encode 16 different characters, plus an additional 4 start/stop characters (A, B, C, D). It was developed in 1972 by Pitney Bowes, Inc.
Since Codabar is self-checking, there is no established checksum digit.