A method for processing an instruction word in a data processing system, the instruction word comprising a plurality of instruction bit positions, each bit position corresponding to an instruction actions, and a status of the bit at an instruction bit position indicating whether the instruction action corresponding to that bit position should be performed; the method comprising: forming a plurality of single action words, each single action word corresponding to one of the instruction actions and having a bit set at the bit position corresponding to that instruction actions and all its other bits un-set; forming a common action word having bits set at the bit positions corresponding to the instruction actions of any of the single action words and all its other bits un-set; comparing the instruction word and the common action word, and if the instruction word and the common action word have no bits set in common terminating processing of the instruction, and otherwise: repeating for successive single action words the steps of: comparing the instruction word and the respective single action word, and if the instruction word and the respective single action word have a bit set in common, performing the action corresponding to that single action word, and setting the instruction word to be equal to the present value of the instruction word exclusive-Ored with the respective single action word; until all the bits in the instruction word are zero.