ARITHMETIC UNIT

PURPOSE:To increase the arithmetic speed by using a non-numeral arithmetic circuit, a non-numeral generating circuit and a selector and decreasing software processes when a calculation is carried out in case at least one of both operands is non-numerical. CONSTITUTION:A non-numeral arithmetic circuit 840 detects a non-numeral and selects an output. A non-numeral generating circuit 860 produces six types of non-numeral bit patterns which are defined a real number value displaying method based on the double exponent division. A selector 870 selects and delivers one of six types of non-numerals given from the output of a normal addition circuit 810 which performs an addition via an output selecting circuit 845 in the circuit 840, the 1st and 2nd operands, and the circuit 860 respectively. With provision of circuits 840 and 860, no interruption is needed for calculation which is carried out in case at least one of both operands is non-numerical. This device decreases the software processes and increases the arithmetic speed.