Hello

I'm a programming newbie. In fact, this is my second code ever (after the hello world code).

I did a lot of reading actually, here on stack overflow, and other websites, I also purchased "Jumping Into C++" By Alex Allain, And I put Everything I learned here In this code :

Simple Calculator.cpp :

#include <iostream>
#include <string>
using std::cout; using std::cin;

int main()
{
cout << "Calculator..... \n";
cout << "Type '3a3'to exit... \n";

double a=0 ,b=0;
char op = 'a'; //operator // 'a' is the exit operator, the value of the integers doesn't matter

int ch = 0; //while loop checker

do
{
    cin >> a >> op >> b;
    if (op == '/' && b == 0)
    {
        cout << "Division By Zero, Please Retry \n" ;
        goto retry;
    }
    switch (op)
    {
        case '+':
        cout << a << " + "<< b << " = " << a+b << "\n";
        ch = 0 ;
        break;

        case '-':
        cout << a << " - "<< b << " = " << a-b << "\n";
        ch = 0 ;
        break;

        case 'x':
        case '*':
        cout << a << " * "<< b << " = " << a*b << "\n";
        ch = 0 ;
        break;

        case '/':
        cout << a << " / "<< b << " = " << a/b << "\n";
        ch = 0;
        break;

        case 'a':
        ch = 1;
        break;

        default:
        ch = 0;
        cout << "Invalid operator, Please retry \n";
    }

    retry: ;

}while (ch != 1);

}

I would Like To know If there's a way to further improve this code.

Thanks In Advance