So I created a code to work as a calculator.

It says that the code doesn't work because sum is not defined. I defined it though in the beginning so it has a default value of 0 and in the def "start". Can anyone tell me what I did wrong?

```
def cal
#calculator vars-----------------------
sum = 0
#Calculators Defs----------------------
def start
puts "Give me a number please!"
num1 = Integer(gets.chomp)
puts ""
puts "Now I need another number"
num2 = Integer(gets.chomp)
puts ""
puts "Now what do you want to do with those numbers. Add(+), Subtract(-), Multiply(*) or Divide(/)?"
op = gets.chomp
until op == "*" or op == "+" or op == "/" or op == "-"
puts ""
puts "You need to choose one of the following! (*,/,-,+)"
op == gets.chomp
end
if op == "*"
sum = num1 * num2
elsif op == "/"
sum = num1 / num2
elsif op == "+"
sum = num1 + num2
elsif op == "-"
sum = num1 - num2
else
puts "Error! Something went wrong in the if statement in the start method!"
end
puts ""
end
def add
puts "Give me another number please!"
num2 = gets.chomp
sum = sum + num2
end
def multiply
puts "Give me another number please!"
num2 = gets.chomp
sum = sum * num2
end
def subtract
puts "Give me another number please!"
num2 = gets.chomp
sum = sum - num2
end
def divide
puts "Give me another number please!"
num2 = gets.chomp
sum = sum / num2
end
puts "///////////////////////////////"
puts "// Calculator //"
puts "///////////////////////////////"
puts "Welcome to the calculator!"
start
puts "The total of your numbers right now are #{sum}"
puts "Are you done with the program(Y/N)?"
title = gets.chomp
until title == "Y" or title == "y"
puts ""
puts "Pick what you want to do!"
puts "1 = Add on to the sum!"
puts "2 = Multiply another number with the sum!"
puts "3 = Subtract a number from the sum!"
puts "4 = Divide another number by the sum!"
puts "5 = Show the sum of numbers!"
abcd = Integer(gets.chomp)
until abcd == 1 or abcd == 2 or abcd == 3 or abcd == 4 or abcd == 5
puts ""
puts "Error! You have to choose by typing in 1, 2, 3, 4 or 5!"
abcd = Integer(gets.chomp)
end
if abcd == 1
add
elsif abcd == 2
multiply
elsif abcd == 3
subtract
elsif abcd == 4
divide
elsif abcd == 5
puts "The sum of all your numbers is #{sum}"
else
puts ""
puts "Error! Something went wrong in the if statement in the decide method!"
end
puts "Are you done with the program(Y/N)?"
title = gets.chomp
end
end
```