addition operation then the alu 14 adds u201c x1 u201d to u201c y1 u201d x1 y1 and adds u201c x2 u201d to u201c y2 u201d x2 y2 fig4 when the instruction indicates a subtraction operation then the alu 14 subtracts u201c y2 u201d from u201c x1 u201d x1 u2212 y2 and subtracts u201c y1 u201d from u201c x2 u201d x2 u2212 y1 fig5 when the instruction indicates a multiplication operation then the alu 14 multiplies u201c x1 u201d by u201c y1 u201d x1 u00d7 y1 multiplies u201c x1 u201d by u201c y2 u201d x1 u00d7 y2 multiplies u201c x2 u201d by u201c y1 u201d x2 u00d7 y1 and multiplies u201c x2 u201d by u201c y2 u201d x2 u00d7 y2 fig6 when the instruction indicates a division operation then the alu 14 divides u201c x1 u201d by u201c y1 u201d x1 y1 divides u201c x1 u201d by u201c y2 u201d x1 y2 divides u201c x2 u201d by u201c y1 u201d x2 y1 and divides u201c x2 u201d by u201c y2 u201d x2 y2 fig7 subsequently the operation result selecting section 15 compares the operation results supplied from the alu 14 according to the instruction from the control section 16 and selects only the operation result s satisfying a predetermined condition the operation result selecting section 15 then writes the selected operation result s in the data memory 12 steps s 70 and s 80 more specifically the operation result selecting section 15 performs one of the following operations depending on what is required by the instruction received from the control section 16 when the instruction indicates an addition operation then the operation result selecting section 15 uses u201c x1 y1 u201d.