Can someone make this calculator work?

Question

https://code.sololearn.com/cRkyyr33hOjI/?ref=app

Answer 1

Here is a shortened version
https://code.sololearn.com/cj7B97M5IXHa/?ref=app

Answer 2

You have initialized the variable op but have not given it a value. You can use cin >> op; so the user can give it the value.