#include <iostream>

using namespace std;

void call_by_value(int a)
{
	cout<<__func__<<": a="<<a<<endl;
	a = 20;
}

void call_by_address(int *a)
{
	cout<<__func__<<": a="<<*a<<endl;
	*a = 30;
}

void call_by_reference(int& a)
{
	cout<<__func__<<": a="<<a<<endl;
	a = 40;
}

int main()
{
	int n = 10;
	call_by_value(n);
	cout<<"after call_by_value:     n="<<n<<endl;
	call_by_address(&n);
	cout<<"after call_by_address:   n="<<n<<endl;
	call_by_reference(n);
	cout<<"after call_by_reference: n="<<n<<endl;

	return 0;
}