This document describes an ISO 8583 decoder user-defined function (UDF) for MySQL. The UDF allows MySQL to parse ISO 8583 message fields and retrieve data elements. To install the UDF, users can either manually copy the DLL file to the MySQL bin folder and run SQL commands, or use an installer program that prompts for the root password before installing. The ISO8583 function syntax extracts data from an ISO message based on the bit number, and optionally the ISO version.