MASKED ARITHMETIC LOGIC UNIT

An improved masked arithmetic logic unit is disclosed which incorporates at least three principle unique features to optimize implementation in a high speed environment. These features are (1) the inclusion of a mask operand to facilitate mask compares and mask substitute operations without adding logic levels to the arithmetic logic unit; (2) the inclusion of a sum minus one network to speed up system performance by minimizing the delay usually associated with group borrow input to final sum output and (3) the inclusion of a mode control register internal to the arithmetic logic unit to minimize or camouflage the delay always found in the mode switching control of contemporary arithmetic logic units.