Code 39

A Code 39 Barcode Label

"WIKIPEDIA" encoded in Code 39

Code 39 (also known as Alpha39, Code 3 of 9, Code 3/9, Type 39, USS Code 39, or USD-3) is a variable length, discrete barcode symbology.

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). An additional character (denoted '*') is used for both start and stop delimiters. Each character is composed of nine elements: five bars and four spaces. Three of the nine elements in each character are wide (binary value 1), and six elements are narrow (binary value 0). The width ratio between narrow and wide can be chosen between 1:2 and 1:3.

The barcode itself does not contain a check digit (in contrast to—for instance—Code 128), but it can be considered self-checking on the grounds that a single erroneously interpreted bar cannot generate another valid character. Possibly the most serious drawback of Code 39 is its low data density: It requires more space to encode data in Code 39 than, for example, in Code 128. This means that very small goods cannot be labeled with a Code 39 based barcode. However, Code 39 is still widely used and can be decoded with virtually any barcode reader. One advantage of Code 39 is that since there is no need to generate a check digit, it can easily be integrated into existing printing system by adding a barcode font to the system or printer and then printing the raw data in that font.

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.^[1] Punctuation characters were later added that deviated from this pattern, expanding the character set to 43 characters. Code 39 was later standardised as ANSI MH 10.8 M-1983 and MIL-STD-1189.^[2] MIL-STD-1189 has been cancelled and replaced by ANSI/AIM BC1/1995, Uniform Symbology Specification - Code 39.^[3]

Encoding

The * character presented below is not a true encodable character, but is the start and stop symbol for Code 39. The asymmetry of the symbol allows the reader to determine the direction of the barcode being scanned. This code is traditionally mapped to the * character in barcode fonts and will often appear with the human-readable representation alongside the barcode.

These tables outline the Code 39 specification:

Code 39 Characters

Legend
Format1	Format2	Desc
W	B	Wide - Black
N	b	Narrow - Black
w	W	Wide - White
n	w	Narrow - White

(Note, Format1 and Format2 are just two different ways of describing the same underlying encoding, not two variants of Code 39.)

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Code Details
Char nr for checksum	Char	Format1	Format2
0	0	NnNwWnWnN	bwbWBwBwb
1	1	WnNwNnNnW	BwbWbwbwB
2	2	NnWwNnNnW	bwBWbwbwB
3	3	WnWwNnNnN	BwBWbwbwb
4	4	NnNwWnNnW	bwbWBwbwB
5	5	WnNwWnNnN	BwbWBwbwb
6	6	NnWwWnNnN	bwBWBwbwb
7	7	NnNwNnWnW	bwbWbwBwB
8	8	WnNwNnWnN	BwbWbwBwb
9	9	NnWwNnWnN	bwBWbwBwb
10	A	WnNnNwNnW	BwbwbWbwB
11	B	NnWnNwNnW	bwBwbWbwB
12	C	WnWnNwNnN	BwBwbWbwb
13	D	NnNnWwNnW	bwbwBWbwB
14	E	WnNnWwNnN	BwbwBWbwb
15	F	NnWnWwNnN	bwBwBWbwb
16	G	NnNnNwWnW	bwbwbWBwB
17	H	WnNnNwWnN	BwbwbWBwb
18	I	NnWnNwWnN	bwBwbWBwb
19	J	NnNnWwWnN	bwbwBWBwb
20	K	WnNnNnNwW	BwbwbwbWB
21	L	NnWnNnNwW	bwBwbwbWB
22	M	WnWnNnNwN	BwBwbwbWb
23	N	NnNnWnNwW	bwbwBwbWB
24	O	WnNnWnNwN	BwbwBwbWb
25	P	NnWnWnNwN	bwBwBwbWb
26	Q	NnNnNnWwW	bwbwbwBWB
27	R	WnNnNnWwN	BwbwbwBWb
28	S	NnWnNnWwN	bwBwbwBWb
29	T	NnNnWnWwN	bwbwBwBWb
30	U	WwNnNnNnW	BWbwbwbwB
31	V	NwWnNnNnW	bWBwbwbwB
32	W	WwWnNnNnN	BWBwbwbwb
33	X	NwNnWnNnW	bWbwBwbwB
34	Y	WwNnWnNnN	BWbwBwbwb
35	Z	NwWnWnNnN	bWBwBwbwb
36	-	NwNnNnWnW	bWbwbwBwB
37	.	WwNnNnWnN	BWbwbwBwb
38	(space)	NwWnNnWnN	bWBwbwBwb
39	$	NwNwNwNnN	bWbWbWbwb
40	/	NwNwNnNwN	bWbWbwbWb
41	+	NwNnNwNwN	bWbwbWbWb
42	%	NnNwNwNwN	bwbWbWbWb
	*	NwNnWnWnN	bWbwBwBwb

Please Note: In between each character (the start and stop characters included) there is a thin space (shown as w below). For example, if you wanted a Code 39 barcode composed of the letter "A", you would need the following to be encoded (using Format 2 as described above): "*A*". [bWbwBwBwb]w[BwbwbWbwB]w[bWbwBwBwb]
The code will not be read without these spaces. Barcode fonts invariably include this space within the glyph for the character.

Code 39 mod 43

Code 39 is sometimes used with an optional modulo 43 check digit. Using it requires this feature to be enabled in the barcode reader. The code with check digit is referred to as Code 39 mod 43.

Here is how to do the checksum calculation:

• Take the value (0 through 42) of each character in the barcode excluding start and stop codes.
• Sum the values.
• Divide the result by 43.
• The remainder is the value of the checksum character to be appended.

Full ASCII Code 39

Code 39 is restricted to 43 characters. In Full ASCII Code 39 Symbols 0-9, A-Z, "." ,and "-" are the same as their representations in Code 39. Lower case letters, additional punctuation characters and control characters are represented by sequences of two characters of Code 39.

Code Details

Nr

Character

Encoding

Nr

Character

Encoding

Nr

Character

Encoding

Nr

Character

Encoding

0

NUL

%U

32

[space]

[space]

64

@

%V

96

`

%W

1

SOH

$A

33

!

/A

65

A

A

97

a

+A

2

STX

$B

34

"

/B

66

B

B

98

b

+B

3

ETX

$C

35

#

/C

67

C

C

99

c

+C

4

EOT

$D

36

$

/D

68

D

D

100

d

+D

5

ENQ

$E

37

%

/E

69

E

E

101

e

+E

6

ACK

$F

38

&

/F

70

F

F

102

f

+F

7

BEL

$G

39

'

/G

71

G

G

103

g

+G

8

BS

$H

40

(

/H

72

H

H

104

h

+H

9

HT

$I

41

)

/I

73

I

I

105

i

+I

10

LF

$J

42

*

/J

74

J

J

106

j

+J

11

VT

$K

43

+

/K

75

K

K

107

k

+K

12

FF

$L

44

,

/L

76

L

L

108

l

+L

13

CR

$M

45

-

-

77

M

M

109

m

+M

14

SO

$N

46

.

.

78

N

N

110

n

+N

15

SI

$O

47

/

/O

79

O

O

111

o

+O

16

DLE

$P

48

0

0

80

P

P

112

p

+P

17

DC1

$Q

49

1

1

81

Q

Q

113

q

+Q

18

DC2

$R

50

2

2

82

R

R

114

r

+R

19

DC3

$S

51

3

3

83

S

S

115

s

+S

20

DC4

$T

52

4

4

84

T

T

116

t

+T

21

NAK

$U

53

5

5

85

U

U

117

u

+U

22

SYN

$V

54

6

6

86

V

V

118

v

+V

23

ETB

$W

55

7

7

87

W

W

119

w

+W

24

CAN

$X

56

8

8

88

X

X

120

x

+X

25

EM

$Y

57

9

9

89

Y

Y

121

y

+Y

26

SUB

$Z

58

:

/Z

90

Z

Z

122

z

+Z

27

ESC

%A

59

;

%F

91

[

%K

123

{

%P

28

FS

%B

60

<

%G

92

\

%L

124

|

%Q

29

GS

%C

61

=

%H

93

]

%M

125

}

%R

30

RS

%D

62

>

%I

94

^

%N

126

~

%S

31

US

%E

63

?

%J

95

_

%O

127

DEL

%T, %X, %Y, %Z

References

1. ^ Allais, D. C. (2006) (PDF). AIDC Memoirs. http://aidc100.org/files/Allais-_David_Memoirs.pdf. 
2. ^ "MIL-STD-1189 Standard Department of Defense Barcode Symbology". 1989-08-10. https://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=36123. Retrieved 2010-07-22. 
3. ^ "AIM/BC1 Uniform Symbology Specification". 1997-06-19. http://www.dscp.dla.mil/subs/support/specs/crds/milstan.asp. Retrieved 2011-04-06.