Something

/* Hypothetical thingy */

//in main.cpp they're declared:
    int a;
    int b;

//in main.cpp they're initialized:
    a = 3;
    b = 2;

//in a function in addnums.c they're accessed:
void addnumbers(int number1, int number2)
{
    number1 = a;
    number2 = b;
}

//the function in addnums.cpp is never called in main, only in addnums.cpp itself.
//
// How do I let it access a and b?  (can't pass them to the function)