Написать калькулятор с определение деления на ноль- QBasic(Бейсик)

CLS
DO
    INPUT "Enter first value: ", c1
    INPUT "Enter operation(+,-,*,/): ", c2$
    INPUT "Enter second value: ", c3
LOOP UNTIL INSTR("+-*/", MID$(c2$, 1, 1))
IF c2$ = "+" THEN c4 = c1 + c3
IF c2$ = "/" THEN
    IF c3 <> 0 THEN c4 = c1 / c3 ELSE PRINT "division by zero": END
END IF
IF c2$ = "*" THEN c4 = c1 * c3
IF c2$ = "-" THEN c4 = c1 - c3
 
PRINT c4