C++简单计算器

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
   double num1, num2;
   char op;//操作符号
   double result;
   char caption1[20] = "Error,Divided by 0!";
   char caption2[20] = "Invalid opereator! ";
   cout << "please input the expression: ";
   cin >> num1 >> op >>num2;
   switch(op)
   {
        case '+' :
            result = num1 + num2 ;
            cout << num1 << " " << op << " " << num2 << " = " << result << endl;
        break;

        case '-' :
            result = num1 - num2;
            cout << num1 << " " << op << " " << num2 << " = " << result << endl;
        break;

        case '*' :
            result = num1 * num2;
            cout << num1 << " " << op << " " << num2 << " = " << result << endl;
        break;

        case '/':
            if(num2 == 0)
            {
                cout << caption1 << endl;
            }
            else
            {
                result = num1 / num2;
                cout << num1 << " " << op << " " << num2 << " = " << result << endl;
                break;
            }
        default :
            cout << caption2 << endl;


   }



    return 0;
}