#include "stdafx.h"
#include <iostream>
#include <string>
using std::cout;
using std::endl;
using std::cin;
using std::string;
int main(void)
{
    char chars1[20];
    char chars2[20] = "jaguar";
    string str1;
    string str2 = "pather";
    cout << "Enter a kind of feline: " << endl;
    cin 
 
>> chars1;
    cout << "Enter another kind of feline: " << endl;
    cin >> str1;
    cin.get();
    return 0;
}

上面的程序如果沒有#include<string>，則cin>>str1將會報錯，而string str1不會報錯，那麽std::string是在哪裏定義的？

頭文件之間的包含關系如下

#include <iostream>

#include <istream>

#include <ostream>

#include <ios>

#include <xlocnum>

#include <cstdio>

#include <yvals.h>

在iostream裏，使用了宏_STD_BEGIN，該宏是定義在yvals.h裏的

std::string 是什麽