Addition with running total

[verandaguy]

I'm trying to write a program which works like a calculator, keeping the running total of an operation, with the number of terms not defined by the user. Here's what I've got so far:

int add(num1,num2)  // these vars are init'd earlier in the program flow
{
    cout << "Enter an operation";
    while (1)
    {
        scanf("%d%c%d",&num,&op,&num2);
        if (strcmp(&op,'+') == 0)
        {
            num2 += num1    // num2 becomes the sum of num1 and num2
            cout << num2
        }

        if (strcmp(&op,'–') == 0)
        {
            // code for subtraction, similar to above
        }
    }
}

I know that this code is incomplete, in that it doesn't loop back to scanning for another "+" and another number; I'm not sure which condition to run the loop under. Can anyone suggest how this can be done?

EDIT: added conditional to better illustrate point

[ADTR2012]

So just to clarify, you need a program that will add numbers and keep a sum? For example if I entered 1 12 4 5 it would output 22? Also how do you want the program to know when to stop? When the user inputs 0?

[verandaguy]

Actually, I've got another condition (which I omitted here because it's irrelevant) where the program stops when the user types exit (I elevate it to uppercase, then use strcmp().
And what you're describing is approximately what I want, but I wanted the user to have the option to use a different sign (+,–,*,/) depending on what operation would be used (I'll handle that with strcmp() for the &op variable and a conditional program flow).