calculator.cpp

#include <iostream>
using namespace std;

int main()
{
    int flag;
    long int a, b;
    long double result;
    char operation;

    cout << "input two Integers(one space between them), then press Enter:" << endl;
    while(cin >> a >> b){
        cout << "input +, -, *, or / , then press Enter: " << endl;
        cin >> operation;
        if (0 == b && '/' == operation) 
        {
            cout << "error: integer division by zero" << endl;
        }

        else
        {
            flag = 0;
            switch(operation)
            {
                case '+':
                    result = a + b;
                    break;

                case '-':
                    result = a - b;
                    break;

                case '*':
                    result = a * b;
                    break;

                case '/':
                    result = (double)a / (double)b;
                    break;

                default:
                    cout << "Invalid operation. Program terminated." << endl;
                    flag = 1;
                    break;
            }

            if (0 == flag)
            {
                cout << result << endl;
            }
        }
        cout << "to continue: input two Integers(one space between them), then press Enter;" 
            << endl << "to stop: press ctrl-C" << endl;
    }
    return 0;
}