Chapter1
P6, 1.2 Why //#include<string> we still can use "string user_name"?
-->ctrl+left mouse on the string of "string user_name", you can find string defined in "stringfwd.h"
ctrl+left mouse on std of "using namespace std", you can find std include "stringfwd.h"
Note1: cout<<"enter...\n"; equal to cout<<"endter..."<<endl;
P7, 1.3 if change main to my_main(), what will happen?
-->ld error, undefined ‘main‘ in function ‘_start‘
Note2: don‘t forget "constructor syntax" for initialization, example: int age(10); it works not only for class.
原文：https://www.cnblogs.com/feliz/p/11552544.html