| Code128 Structure (From left to right) |
|---|
| A start character |
| Message encoded |
| Check character |
| Stop Character |
| Termination bar (bar+space+bar) |
Code 128 is of variable length and encodes a full 128 ASCII character set. Each character is represented by 11 modules that can be one of four bar widths. Also, the encoding should not exceed 232 characters (including the starting and ending codes).
Among all the common linear symbologies, Code 128 is the most flexible. It supports both alpha and numeric characters easily, has the highest number of characters per inch, and is of variable length. Code 128 is usually the best choice when implementing a new symbology.
Check code is optional. Refer to the Code 128 code table to calculate it.
In an open system, the minimum value of the X dimension is 7.5 mils, and the minimum bar height is 15 percent of the symbol length or 0.25 inches, whichever is greater. The starting and trailing quiet zones are at least 0.25 inches wide.