C++学习笔记（2）作用域

#include<iostream>
int a = 10;
int main()
{
    int    i = 10;
    std::cout<<"a = "<< a<<", i =  " << i <<std::endl;
    int a = 20;                  //局部变量取代全局变量
    std::cout<<"a = "<< a<<", i =  " << i <<std::endl;
    std::cout<<"a = "<< ::a<<", i =  " << i <<std::endl;
    return 0;
}

输出结果:a = 10,i = 10;
             a = 20,i = 10;
             a= 10,i = 10;