1. Apparatus for processing data under control of a set of program instructions that map upon interpretation to data processing operations to be performed, said apparatus comprising: (i) a fixed mapping hardware interpreter operable to interpret a fixed mapping group of said set of program instructions, whereby a program instruction from said fixed mapping group maps to a fixed sequence of one or more data processing operations; and (ii) a programmable mapping hardware interpreter operable to interpret a programmable mapping group of said program instructions, whereby a program instruction from said programmable mapping group maps to a sequence of one or more data processing operation that varies in dependence upon programming of said programmable mapping hardware interpreter.