function_pointers.cpp

//using of functions with the pointers.
#include <iostream>
using namespace std;

// scope of variable..
int call_value ( int );
int call_reference ( int *, int *, int * );

int main (){

    int p = 10, q = 20, r = 30;   // memory allocation is necessary for not getting of segmentation fault.

    // this function means is basically that variables copy.
    call_value ( p );             // this code return 10.
    cout << p << endl;            // a and x are different variable and this ram memory adresses are different.

    // it is possible that a lot of returned value in functions with call by reference.
    call_reference ( &p, &q, &r );
    cout << p << " " << q << " " << r << endl;

    return 0;
}

// scope of variable..
int call_value ( int x ){         // call by value
    x = 30;                       // this x value is only defined between of this brackets.
}
int call_reference ( int *x, int *y, int *z ){    // call by reference
    *x = *y * 30;
    *y = *x * 40;                      // this x, y, z value is defined when this pointers are called.
    *z = 20;
}