Spatula Systems - Nick Johnson's Barcode Specifications

Extrapolated Barcode Specs

Compiled by Nick Johnson.

Code 3 of 9

By far, these are the most heinous barcodes out there, mostly because of the large number of characters that can be represented with Code 39. Built into the coding scheme are all the digits and capital letters as well as the control characters *, $, /, +, and %, and space, hyphen, and period. Additional characters can be produced by combining control characters with data characters if the reader is to be operating in full ASCII mode (otherwise the characters are interpreted literally).

Each character is made up of 5 bars and 4 spaces. 3 of these 9 elements will be wide (this is where the code gets its name) and 6 narrow. The result is a character of consistant width as in EAN above. Each character is also assigned a numeric value to be used for calculating the checksum. Here are the wide and narrow vaules for the 43 characters:

Char Value B1 S1 B2 S2 B3 S3 B4 S4 B5
1 1 W N N W N N N N W
2 2 N N W W N N N N W
3 3 W N W W N N N N N
4 4 N N N W W N N N W
5 5 W N N W W N N N N
6 6 N N W W W N N N N
7 7 N N N W N N W N W
8 8 W N N W N N W N N
9 9 N N W W N N W N N
0 0 N N N W W N W N N
A 10 W N N N N W N N W
B 11 N N W N N W N N W
C 12 W N W N N W N N N
D 13 N N N N W W N N W
E 14 W N N N W W N N N
F 15 N N W N W W N N N
G 16 N N N N N W W N W
H 17 W N N N N W W N N
I 18 N N W N N W W N N
J 19 N N N N W W W N N
K 20 W N N N N N N W W
L 21 N N W N N N N W W
M 22 W N W N N N N W N
N 23 N N N N W N N W W
O 24 W N N N W N N W N
P 25 N N W N W N N W N
Q 26 N N N N N N W W W
R 27 W N N N N N W W N
S 28 N N W N N N W W N
T 29 N N N N W N W W N
U 30 W W N N N N N N W
V 31 N W W N N N N N W
W 32 W W W N N N N N N
X 33 N W N N W N N N W
Y 34 W W N N W N N N N
Z 35 N W W N W N N N N
- 36 N W N N N N W N W
. 37 W W N N N N W N N
38 N W W N N N W N N
* (none) N W N N W N W N N
$ 39 N W N W N W N N N
/ 40 N W N W N N N W N
+ 41 N W N N N W N W N
% 42 N N N W N W N W N

Char	Value	B1	S1	B2	S2	B3	S3	B4	S4	B5
1	1	W	N	N	W	N	N	N	N	W
2	2	N	N	W	W	N	N	N	N	W
3	3	W	N	W	W	N	N	N	N	N
4	4	N	N	N	W	W	N	N	N	W
5	5	W	N	N	W	W	N	N	N	N
6	6	N	N	W	W	W	N	N	N	N
7	7	N	N	N	W	N	N	W	N	W
8	8	W	N	N	W	N	N	W	N	N
9	9	N	N	W	W	N	N	W	N	N
0	0	N	N	N	W	W	N	W	N	N
A	10	W	N	N	N	N	W	N	N	W
B	11	N	N	W	N	N	W	N	N	W
C	12	W	N	W	N	N	W	N	N	N
D	13	N	N	N	N	W	W	N	N	W
E	14	W	N	N	N	W	W	N	N	N
F	15	N	N	W	N	W	W	N	N	N
G	16	N	N	N	N	N	W	W	N	W
H	17	W	N	N	N	N	W	W	N	N
I	18	N	N	W	N	N	W	W	N	N
J	19	N	N	N	N	W	W	W	N	N
K	20	W	N	N	N	N	N	N	W	W
L	21	N	N	W	N	N	N	N	W	W
M	22	W	N	W	N	N	N	N	W	N
N	23	N	N	N	N	W	N	N	W	W
O	24	W	N	N	N	W	N	N	W	N
P	25	N	N	W	N	W	N	N	W	N
Q	26	N	N	N	N	N	N	W	W	W
R	27	W	N	N	N	N	N	W	W	N
S	28	N	N	W	N	N	N	W	W	N
T	29	N	N	N	N	W	N	W	W	N
U	30	W	W	N	N	N	N	N	N	W
V	31	N	W	W	N	N	N	N	N	W
W	32	W	W	W	N	N	N	N	N	N
X	33	N	W	N	N	W	N	N	N	W
Y	34	W	W	N	N	W	N	N	N	N
Z	35	N	W	W	N	W	N	N	N	N
-	36	N	W	N	N	N	N	W	N	W
.	37	W	W	N	N	N	N	W	N	N
	38	N	W	W	N	N	N	W	N	N
*	(none)	N	W	N	N	W	N	W	N	N
$	39	N	W	N	W	N	W	N	N	N
/	40	N	W	N	W	N	N	N	W	N
+	41	N	W	N	N	N	W	N	W	N
%	42	N	N	N	W	N	W	N	W	N

W=wide, N=narrow

You can grab a copy of the translation table here.

To calculate the check digit, add the values of all the digits and take the modulus 43 of that sum. So if the sum was 178, the digit would be 6.

The checksum is rarely used because the code inherently checks itself; anything that doesn't match the 3 of 9 format is discarded as a bad scan.

All Code39 barcodes begin and end with the * control character and should not exceed 32 characters, including the start and stop characters as well as the check character. The wide to narrow ratio should be between 2.25:1 and 3:1. Also, the Characters per inch should be between 2.3 and 9.4, with 4.7 being fairly typical. This means having 75.2 X-dimensions per inch. The X-dimension is the fundamental element that the narrow bars, spaces, and often the intercharacter gap are based on.

Codabar	Code 2 of 5	Code 3 of 9	Interleaved 2 of 5
Postnet	UPC	Code 128	Code 16k


Mon Feb 8 22:51:33 PST 2010		barcode/code39.src
Updated: Thu Aug 18 2005 9:31.35		Viewed: never