#include <iostream>
#include <string>
int main()
{
    const std::string cS ("c.biancheng.net");
    std::string s ("abode");
    char temp =0;
    char temp_1 = 0;
    char temp_2 = 0;
    char temp_3 = 0;
    char temp_4 = 0;
    char temp_5 = 0;
    temp = s [2]; //"获取字符 ‘c‘
    temp_1 = s.at(2); //获取字符 ‘c‘
    temp_2 = s [s.length()]; //未定义行为，返回字符‘\0‘，但Visual C++ 2012执行时未报错
    temp_3 = cS[cS.length()]; //指向字符 ‘\0‘
    temp_4 = s.at (s.length ()); //程序异常
    temp_5 = cS.at(cS.length ()); //程序异常
    std::cout << temp <<temp_1 << temp_2 << temp_3 << temp_4 << temp_5 << std::endl;
    return 0;
}