What is the output?

int ax(int);

int by(int);

int x = 6;

int main( ) {

int x = 3;

int y = 1;

y = ax(x);

cout << " return ax = " << y;

cout <<" return by = "<< by(x) << endl;

return 0;

}

int ax(int p) {

cout << " p = "<

return x;

}

int by(int x)

{

x *= 3;

if (x > 5) {

return x;

}

else {

return x*=4;

}

}

What is the call by reference?

How could the program above be modified so that the by( ) Function uses call-by-reference to also change the main( ) x whenever changes in the Function occur?