how to make calculator using wpl software

M0 = COMMON INPUT, D10 = DATA REGISTER USED IN COMPARATOR( EQUAL TO COMPARATOR) K1,K2,K3,K4 = CONSTANT VALUE, D0 = DATA REGISTOR AS INPUT 1, D2 = DATA REGISTOR AS INPUT 2, D4 = STORE RESULT VALUE , AND AT LAST K0 IS USED TO MOVE THE VALUE OF D4 TO 0 WHEN M0 IS OFF. HOW IT WORKS, WHEN M0 IS ENABLE, AND VALUE OF D10 IS 2 , NOW IF VALUE OF D0 IS 10 AND D2 IS 3 THEN OUTPUT RESULT IN D4 IS 7. NOW IF YOU OFF THE M0 THEN ONLY VALUE OF D4 BECOME ZERO.