TEXT encodes three alphanumeric data characters into two bytes. Structured Append is used to link information from several symbols in a secuence. The first 4 bits of thie first byte identify the position of the particular symbol in the secuence . The last 4 bits identify the total number of symbols in the secuence. It indicates that the data contains commands for the barcode reader.
Extended channel is used for using other character sets other than ascii.