Abstract: A method for optimising application program code including a plurality of fixed point variables. Each fixed point variable comprises a binary pattern. The binary pattern has an integer portion having an integer word length (IWL) and a fractional portion having a fractional word length (FWL). The method comprises simulating execution of the application to identify any variables to which values having a greater IWL are assigned and modifying the code to increase the IWL of those variables by an amount required to prevent overflow errors.