Code 39

• Code 39 (or Code 3 of 9) differs from most of the other popular bar code symbologies in that it is alphanumeric.
• The Code 39 specification defines 43 characters, consisting of uppercase letters (A through Z), numeric digits (0 through 9) and a number of special characters (-, ., $, /, +, %, and space).
• It is the standard bar code used by the United States Department of Defense, and is also used by the Health Industry Bar Code Council.

Encoding the symbol

• The number "1" represents a "dark" or "bar" section of the bar code whereas a "0" represents a "light" or "space" section of the bar code.
• Thus the numbers 1101 represents a double-wide bar (11), followed by a single-wide space (0), followed by a single-wide bar (1).

Structure of a Code 39 barcode

• A Code 39 bar code has the following structure:
• A start character - the asterisk (*) character.
• Any number of characters encoded from the table below.
• An optional checksum digit calculated as described above and encoded from the table below.
• A stop character, which is a second asterisk character.

Code 39 Encoding table

• Below table note that the "Width Encoding" column is expressed as "N" for narrow and "W" for wide.
• The "Barcode Encoding" column represents how the bar code will actually be encoded as described above in "Encoding the symbol."
• Keep in mind that each character begins and ends with a bar, thus the "bar code encoding" always starts and ends with a "1".

Check Value	ASCII Char	Width Encoding	Barcode Encoding	Check Value	ASCII Char	Width Encoding	Barcode Encoding
0	0	NNNWWNWNN	101001101101	22	M	WNWNNNNWN	110110101001
1	1	WNNWNNNNW	110100101011	23	N	NNNNWNNWW	101011010011
2	2	NNWWNNNNW	101100101011	24	O	WNNNWNNWN	110101101001
3	3	WNWWNNNNN	110110010101	25	P	NNWNWNNWN	101101101001
4	4	NNNWWNNNW	101001101011	26	Q	NNNNNNWWW	101010110011
5	5	WNNWWNNNN	110100110101	27	R	WNNNNNWWN	110101011001
6	6	NNWWWNNNN	101100110101	28	S	NNWNNNWWN	101101011001
7	7	NNNWNNWNW	101001011011	29	T	NNNNWNWWN	101011011001
8	8	WNNWNNWNN	110100101101	30	U	WWNNNNNNW	110010101011
9	9	NNWWNNWNN	101100101101	31	V	NWWNNNNNW	100110101011
10	A	NNWWNNWNN	110101001011	32	W	WWWNNNNNN	110011010101
11	B	NNWNNWNNW	101101001011	33	X	NWNNWNNNW	100101101011
12	C	WNWNNWNNN	110110100101	34	Y	WWNNWNNNN	110010110101
13	D	NNNNWWNNW	101011001011	35	Z	NWWNWNNNN	100110110101
14	E	WNNNWWNNN	110101100101	36	-	NWNNNNWNW	100101011011
15	F	NNWNWWNNN	101101100101	37	.	WWNNNNWNN	110010101101
16	G	NNNNNWWNW	101010011011	38	SPACE	NWWNNNWNN	100110101101
17	H	WNNNNWWNN	110101001101	39	$	NWNWNWNNN	100100100101
18	I	NNWNNWWNN	101101001101	40	/	NWNWNNNWN	100100101001
19	J	NNNNWWWNN	101011001101	41	+	NWNNNWNWN	100101001001
20	K	WNNNNNNWW	110101010011	42	%	NNNWNWNWN	101001001001
21	L	NNWNNNNWW	101101010011	n/a	*	NWNNWNWNN	100101101101

History

• Code 39 was developed by Dr. David Allais and Ray Stevens of Intermec in 1974.
• Their original design included two wide bars and one wide space in each character, resulting in 40 possible characters.
• Setting aside one of these characters as a start and stop pattern left 39 characters, which was the origin of the name Code 39.