1. Processing system for interpreting and carrying out a set of logically related instructions stored into a software program, an execution of a given instruction by said processing system involving the decoding and the execution of a corresponding set of microcommands, characterized in that it includes: means for storing a signature portion corresponding to a macrocommand portion of a given instruction which is to be interpreted and executed; means for computing a signature data functionally related to a combination of decoded and executed microcommands involved in the execution of said given instruction; and means for comparing said computed signature data with said signature portion in order to detect the occurrence of an error in the execution of said given instruction.