top:

input "choose an operation + - * or / " a$
if a$ = "*" then goto multiply:
if a$ = "+" then goto add:
if a$ = "-" then goto subtract:
if a$ = "/" then goto divide:
else goto top:

multiply:
input "input first number";b
input "input first number";c
let d = b * c
print "your answer is";d
do you want to calculate something else?y/n ";yesno$
if $yesno = "y" then goto top:
else goto end:


add:
input "input first number";b
input "input first number";c
let d = b + c
print "your answer is";d
do you want to calculate something else?y/n ";yesno$
if $yesno = "y" then goto top:
else goto end:

subtract:
input "input first number";b
input "input first number";c
let d = b - c
print "your answer is";d
do you want to calculate something else?y/n ";yesno$
if $yesno = "y" then goto top:
else goto end:

divide:
input "input first number";b
if b = 0 then goto divide:
input "input first number";c
if c = 0 then goto divide:
let d = b / c
print "your answer is";d
do you want to calculate something else?y/n ";yesno$
if $yesno = "y" then goto top:

end: