C++ 無符號整型和整型的區別

　　在Win 7系統中，short 表示的范圍為 - 32767到 32767，而無符號的short表示的范圍為0 到 65535，其他類型的同理可推導出來，當然，僅當數字不為負的時候才使用無符號類型。

　　有些事情，當時接觸的時候模模糊糊，可是，當你在過些時間慢慢的回頭看他時，覺得頓然開悟。

　　下面的程序顯示了如何使用無符號類型，並說明了程序試圖超越整型的限制時所產生的后果。在編寫程序時切記不要超越這些類型所限制的范圍，否則很難找出問題。

#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 << "如果每個數都加一呢？" << 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 << "如果每個數減一呢？" << endl;
    nu1 = nu1 - 1;
    nu2 = nu2 - 1;
    cout << "Now nu1 has " << nu1 << " and nu2 has " << nu2 << endl;
    cin.get();
    return 0;
}  

程序運行結果：　　

　　nu1 has 32767 and nu2 has 32767
　　如果每個數都加一呢？
　　Now nu1 has -32768 and nu2 has 32768

　　nu1 has 0 and nu2 has 0
　　如果每個數減一呢？
　　Now nu1 has -1 and nu2 has 65535