VC++ 禁止运行程序的多个实例，程序根据主窗口类名和主窗口名判断是否已经有实例存在，如果存在就将其激活，并显示出来，如果是最小化的就还原窗口；如果有实例存在，则返回False并退出。

-VC++ prohibits running the program multiple instances of the program under the main window class name and the main window name to determine whether there are examples exist, if it will activate and show, if it is minimized to restore the window　if examples exist, Returns False and exit.