What is a Function Code?
Function (FNC) codes define instructions for a bar code reader decoding Code 128 barcodes. FNC 1, for example, is a required component of the UCC-128 specification. FNC 2 tells the reader to store the data read and transmit it with the next symbol. FNC 3 is reserved for code reader initializing and other reader functions. FNC 4 is reserved for future use.