PURPOSE: To give the freedom to the number of signals due to conditional changes, by providing the means outputting masked signal for the not masked location with mask signal and the means outputting the signal from the information processor with the inverting signal of the mask signal.

CONSTITUTION: The microinstruction including the mask signal and the masked signal is memorized in the microprogram memory set 21, and the output signal 202 of the mask field 32 of instruction of the set 21 and the output signal 203 of the field 31 masked are selected with the address signal 201. The bit of the field 31 corresponding to the bit of the logic value 0 of the field 32 is fed to the synthesis circuit 25 as the signal 205 not masked with the bit mask circuit 22. The signal representing the state in the information processor is delivered from the state delivery circuits 24 and 34, and the conditional signal of the bit of logic 1 of the field 33 is fed to the circuit 25 with the conditional mask circuit 23 based on the mask field 33, and the signal 207 of the field 35 synthesized with the signal 205 at the circuit 25 is stored in the address register 27 of the information processor controller 26.