Codabar normally only encodes the numbers 0-9, but some variants allow :-$.+/., symbols too. It can be reliably reproduced by almost any printer and is widely used for keeping track of items.
It consists of black bars and white bars in two widths: the wide bars are three times the width of the narrow bars.
Pairs of A, B, C or D characters may be used as 'start' and 'stop' characters.
Some organizations have standardized their bar-codes: for example, specifying that every bar-code should contain 13 characters plus a check character.