PURPOSE: To improve performance by reducing the number of operating steps at the time of a branching operation at the microprogram control part of an information processor using a microprogram.

CONSTITUTION: This system is provided with factor registers A11 and B12 for the factors of the branching operation, comparative registers A21 and B22 storing information to be compared with these factor registers, comparison circuit 1 for comparing the factor registers with the comparative registers, branch control part 3 for controlling the branching operation based on the output of the comparison circuit 1, exceptional code register 7 for preserving an exceptional code, and exceptional code generating circuit 5 for generating the exceptional code to be set to the exceptional code register 7. When branching is successful, processing of information is branched to exceptional processing after an arbitrary exceptional code is set to the exceptional code register and when the branching is in fail, the next micro instruction is executed by an exceptional branching instruction to reduce the number of execution steps.