問題描述：

判斷CapsLock，Alt，Ctrl，Shift是否被按下

參考程式碼：

#include <stdio.h>
#include <windows.h>

int main()
{
    while (1)
    {
        short sValue = GetKeyState(VK_CAPITAL);
        if (sValue & 0x1)//該值低位位1，則表示CapsLock按下
            printf("Caps Lock key is on\n");
        else
            printf
 
("Caps Lock key is off\n");

        if (GetKeyState(VK_CONTROL) & 0x8000)//ctrl鍵的判斷方法
            printf("Ctrl key is on\n");
        else
            printf("Left Ctrl key is off\n");

        if (GetKeyState(VK_SHIFT) & 0x8000)//shift鍵的判斷方法
            printf("Shift key is on\n");
        else
            printf
 
("Shift key is off\n");

        if (GetKeyState(VK_MENU) & 0x8000)//alt鍵的判斷方法
            printf("Alt key is on\n");
        else
            printf("Alt key is off\n");

        printf("\n");
        Sleep(1000);
    }
    return 0;
}