Another barcoding scheme is called "39" or "3 of 9", and is in widespread use. Unlike
UPC,
39 is
alphanumeric. A bar of this code
represents a
string of characters. The first and last
characters are always the "START/STOP" character. This allows the code to be scanned in either direction. The code is called 3 of 9 because in each character, 3 elements of the character are wide, while the rest are narrow. For example, here is the start/stop code:
#...#.###.###.#
Note that the start character has 9 elements, either black (#) or white (.). There is one wide white
element, and two wide blacks, totaling 3. Wide elements are three units wide, while narrow elements are one
unit wide. Characters are separated by one narrow white element.Characters which may be represented by code 39:
space, START/STOP, ~, $, %, *, +, Numbers, and uppercase letters.