Guide to Barcode Symbologies

Code 128


Example of Code 128 A

Code 128 A

Example of Code 128 B

Code 128 B

Example of Code 128 C

Code 128 C


A high density, alpha numeric symbology that is used extensively internationally. Out of the linear bar codes. Code 128 probably the easiest of all formats to read and has high message integrity.

Code 128 – variable length, encodes between 20 – 30 characters, dependant on the amount of data to be stored. Full 128 ASCII characters (the complete, US 101 keyboard and many ASCII functions like tab and return) are available, the numeric data encodes at almost double-density when compared with Code 2 of 5. Another feature of Code 128 is that where you require a considerable amount of numeric data in a small space, code 128 is ideal.

Although Code 128 is able to encode the 128 delimited characters, really the character set actually contains 102 characters. The Code 128 really has three sets with 102 characters which are used to give the complete 128 characters. Shown below is a summary of the character sets:

  • Code A: Uses the full ASCII character set, less the lowercase letters (26 in total).
  • Code B: Uses the full ASCII character set, less the control characters (26 in total).
  • Code C: Numeric character set that stores numbers with double the density, each barcode character represents two digits between 00 – 99.
  • Auto: The option switches through code A, B or C within the stored message providing a compact bar code with the given character set. Any (slight) overhead cost that occurs whiles switching inbetween codes, is usually vastly outweighed by space savings.