Code 128 is a variable length, high density, alphanumeric symbology. Code 128 has 106 different bar and space patterns and each pattern can have one of three different meanings, depending on which of three different character sets is employed. Special start characters tell the reader which of the character sets is initially being used and three special shift codes permit changing character sets inside a symbol. One character sets 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 meaning of function code FNC1 and FNC4 were originally left open for application specific purposes. Recently an agreement was made by the Automatic Identification Manufacturers Assoc. (AIM) and the European Article Numbering Assoc. (EAN) to reserve FNC1 for use in EAN applications. FNC4 remains available for use in closed system applications. FNC2 is used to instruct a barcode reader to concatenate the message in a barcode symbol with the message in the next symbol. FNC3 is used to instruct a barcode reader to perform a reset. When FNC3 is encoded anywhere in a symbol, any data also contained in the symbol is discarded.
Note: All TALtech barcode software products will automatically select the proper character sets and insert the necessary start character and shift codes so that the resulting barcode will be as short as possible. The check digit will also be calculated automatically.