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Example of a Code 128 barcode reading 12ab#!

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What is Code 128

Code 128 is a type of barcode that allows for the encoding of alphanumeric data of variable length with high density. It uses 106 different bar and space patterns, and each pattern can have one of three meanings depending on which of three character sets is employed.

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Technical specifications

There are special start characters that indicate which of the character sets is initially being used, and three special shift codes that allow for changing character sets inside a symbol. One character set encodes all upper case and ASCII control characters, another encodes all upper and lower case characters, and the third set encodes numeric digit pairs 00 through 99. This third character set effectively doubles the code density when printing numeric data. Code 128 also employs a check digit for data security. In addition to ASCII characters, Code 128 also allows encoding of four special function codes (FNC1 – FNC4).
  • The meanings of function codes FNC1 and FNC4 were originally left open for application-specific purposes, until the Automatic Identification Manufacturers Association (AIM) and the European Article Numbering Association (EAN) agreed to reserve FNC1 for use in EAN applications.
  • FNC4 remains available for use in closed system applications.
  • FNC2 is used to concatenate the message in a barcode symbol with the message in the next symbol.
  • FNC3 is used to perform a reset. When FNC3 is encoded anywhere in a symbol, any data also contained in the symbol is discarded.

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Using Code 128 with B-Coder Pro

It’s worth noting that B-Coder Pro will automatically select the proper character sets and insert the necessary start character and shift codes to create the shortest possible barcode. Additionally, the check digit is calculated automatically.
Last modified on November 3, 2026