Code 39

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A Code 39 Barcode Label
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A Code 39 Barcode Label

Code 39 (also known as "USS Code 39", "Code 3/9", "Code 3 of 9", "USD-3", "Alpha39") is a barcode symbology that can encode uppercase letters (A through Z), digits (0 through 9) and a handful of special characters like the $ sign. The barcode itself does not contain a check digit (in contrast to—for instance—Code 128), but it can be considered self-checking by some, 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.

Code 39 is called so because it originally consisted of 39 characters (now 43). Code 39 has the alias Code 3 of 9 because there are 9 light and dark bars in each code, and 3 of these bars are wide. 3 "wide" of 9 "bars".

The width ratio between narrow and wide can be chosen between 1:2 and 1:3.

Contents

[edit] 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 3 of 9 specification:


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


Code Details
Char Format1 Format2
* NwNnWnWnN bWbwBwBwb
- NwNnNnWnW bWbwbwBwB
$ NwNwNwNnN bWbWbWbwb
% NnNwNwNwN bwbWbWbWb
(space) NwWnNnWnN bWBwbwBwb
. WwNnNnWnN BWbwbwBwb
/ NwNwNnNwN bWbWbwbWb
+ NwNnNwNwN bWbwbWbWb
0 NnNwWnWnN bwbWBwBwb
1 WnNwNnNnW BwbWbwbwB
2 NnWwNnNnW bwBWbwbwB
3 WnWwNnNnN BwBWbwbwb
4 NnNwWnNnW bwbWBwbwB
5 WnNwWnNnN BwbWBwbwb
6 NnWwWnNnN bwBWBwbwb
7 NnNwNnWnW bwbWbwBwB
8 WnNwNnWnN BwbWbwBwb
9 NnWwNnWnN bwBWbwBwb
A WnNnNwNnW BwbwbWbwB
B NnWnNwNnW bwBwbWbwB
C WnWnNwNnN BwBwbWbwb
D NnNnWwNnW bwbwBWbwB
E WnNnWwNnN BwbwBWbwb
F NnWnWwNnN bwBwBWbwb
G NnNnNwWnW bwbwbWBwB
H WnNnNwWnN BwbwbWBwb
I NnWnNwWnN bwBwbWBwb
J NnNnWwWnN bwbwBWBwb
K WnNnNnNwW BwbwbwbWB
L NnWnNnNwW bwBwbwbWB
M WnWnNnNwN BwBwbwbWb
N NnNnWnNwW bwbwBwbWB
O WnNnWnNwN BwbwBwbWb
P NnWnWnNwN bwBwBwbWb
Q NnNnNnWwW bwbwbwBWB
R WnNnNnWwN BwbwbwBWb
S NnWnNnWwN bwBwbwBWb
T NnNnWnWwN bwbwBwBWb
U WwNnNnNnW BWbwbwbwB
V NwWnNnNnW bWBwbwbwB
W WwWnNnNnN BWBwbwbwb
X NwNnWnNnW bWbwBwbwB
Y WwNnWnNnN BWbwBwbwb
Z NwWnWnNnN 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: "*A*". [bWbwBwBwb]w[BwbwbWbwB]w[bWbwBwBwb]
Make sure that the thin spaces are there! The bar code will not read at all without it!

[edit] Code 39 mod 43

Code 39 is sometimes, though rarely, 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 43.
  • The remainder is the value of the checksum character to be appended.

This can be expressed in Visual Basic as:

Const charSet As String = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-. $/+%"
Function Mod43(C39 As String) As String
  For i = 1 To Len(C39)
    total = InStr(charSet, Mid(C39, i, 1)) - 1 + total
  Next i
  Mod43 = C39 & Mid$(charSet, (total Mod 43 + 1), 1)
End Function

[edit] Full Ascii Code 39

Code 39 is restricted to 44 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 ESQ %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

[edit] External links

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