second class

#include<iostream>
using std::cout;//identifier(名字，标示符) scope(作用域)
using std::cin;// using directive(using指令)
using std::endl;

// pass by value - 传值调用
int add(int x, int y)//形参
{return x+y;}

//pass by address- 传址调用
void swap(int *p,int *q)
{
int temp; // * -
temp=*p;
*p=*q;
*q=temp;
}

//pass by reference 传引用
void swap2(int &a, int &b)
{
int t=a;
a=b;
b=t;
}
int main();
{
int x = 10;
int& cx = x; //cx is a reference(引用) to x;
cx++;
cout<<add(x,cx)<<endl;//argument
}