Code 39
Code 39 is a barcode symbology developed by Intermec in 1969. It is widely used in numerous industries, including libraries and pharmaceuticals. Code 39 is a discrete (the bar(s) encoding one character are contained in a space of specified width) symbology with two different bar widths, a start sequence on its left end and a stop sequence on its right end.
Code 39 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). 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 gets it's name because there are 9 white and black bars in each code, and 3 of these bars are wide. 3 "wide" of 9 "bars".
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 |
| - | 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 |
