C++ 无符号整型和整型的区别

　　在Win 7系统中，short 表示的范围为 - 32767到 32767，而无符号的short表示的范围为0 到 65535，其他类型的同理可推导出来，当然，仅当数字不为负的时候才使用无符号类型。

　　有些事情，当时接触的时候模模糊糊，可是，当你在过些时间慢慢的回头看他时，觉得顿然开悟。

　　下面的程序显示了如何使用无符号类型，并说明了程序试图超越整型的限制时所产生的后果。在编写程序时切记不要超越这些类型所限制的范围，否则很难找出问题。

#include<iostream>
#define ZERO 0
using namespace std;
#include<climits>
int main()
{   
    short nu1 = SHRT_MAX;
    unsigned short nu2 = nu1;
    cout << "nu1 has " << nu1 << " and nu2 has " << nu2 << endl;
    cout << "如果每个数都加一呢？" << endl;
    nu1 = nu1 + 1;
    nu2 = nu2 + 1;
    cout << "Now nu1 has " << nu1 << " and nu2 has " << nu2 << endl<<endl;
    nu1 = ZERO;
    nu2 = ZERO;
    cout << "nu1 has " << nu1 << " and nu2 has " << nu2 << endl;
    cout << "如果每个数减一呢？" << endl;
    nu1 = nu1 - 1;
    nu2 = nu2 - 1;
    cout << "Now nu1 has " << nu1 << " and nu2 has " << nu2 << endl;
    cin.get();
    return 0;
}  

程序运行结果：　　

　　nu1 has 32767 and nu2 has 32767
　　如果每个数都加一呢？
　　Now nu1 has -32768 and nu2 has 32768

　　nu1 has 0 and nu2 has 0
　　如果每个数减一呢？
　　Now nu1 has -1 and nu2 has 65535