Code 11

{{Short description|Barcode symbology}}

Image:code11 barcode.png

Code 11 is a barcode symbology developed by Intermec in 1977, and it is used primarily in telecommunications. The symbol can encode any length string consisting of the digits 0–9 and the dash character (-). A twelfth code represents the start/stop character, commonly printed as "*". One or two modulo-11 check digit(s) can be included.

It is a discrete, binary symbology where each digit consists of three bars and two spaces; a single narrow space separates consecutive symbols. The width of a digit is not fixed; three digits (0, 9 and -) have one wide element, while the others have two wide elements.

The valid codes have one wide bar, and may have one additional wide element (bar or space).

class="wikitable sortable" |+ Code 11 digits ! Character !Widths	Barcode
0 |00001 |101011
1 |10001 |1101011
2 |01001 |1001011
3 |11000 |1100101
4 |00101 |1011011
5 |10100 |1101101
6 |01100 |1001101
7 |00011 |1010011
8 |10010 |1101001
9 |10000 |110101
- |00100 |101101
Stop/Start |00110 |1011001

class="wikitable" style="text-align:center" |+ Code 11 decoding !rowspan=2| Wide element	colspan=3| Wide bar
Left || Middle || Right
Left bar | 9 || 5 || 1
Left space | 3 || 6 || 2
Middle bar | 5 || - || 4
Right space | 8 || * || 7
Right bar | 1 || 4 || 0

The decode table has 15 entries because the symbols with two wide bars (1, 4 and 5) are listed twice.

Assuming narrow elements are one unit wide and wide elements are two units, the average digit is 7.8 units. This is better than codes with a larger repertoire like Codabar (10 units) or Code 39 (11 units), but not quite as good as interleaved 2 of 5 (7 units). The non-binary symbology Code 128 uses 5.5 units per digit (11 units per digit pair).