1. A method of recognising command related items in a body of object code, said command related items corresponding to command names and/or associated option names from a textual programming language; the method comprising: entering a list of entries each comprising a required command name and/or option names in programming language textual form into a filter table; scanning the body of object code for all bit strings potentially representing command names and identifying such command names; for each potential command name so identified, examining a number of succeeding bits for bits which represent valid options for each said command name to further identify commands having valid combinations of command names and options; and for said identified commands, comparing said identified command names and/or option names in programming language textual form with the entries of said filter table to determine whether or not they match any of the list of required command names and/or options in said filter table.