WINDOWS是基于消息的系统，鼠标移动，单击，键盘按键，窗口关闭等都会产生相应的消息，那么钩子是什么意思呢，它可以监控一个消息，比如在一个窗口里单击了一下，首先获得这个消息的，不是应用程序，而是系统，系统获取这个消息后，就去查看这个消息是在哪个窗口产生的，找到窗口后，再把消息投递到相应程序里的消息队列里，这之间有一个传递过程，那么钩子的作用就是在消息到达应用程序之前截获它，钩子可以关联一个函数（钩子处理函数），也就是说，如果对一个进程安装了一个钩子，进程再接收到相应在消息之前，会先去执行钩子所关联的函数，

-WINDOWS is based on message system, mobile mouse, click, keyboard keys, closing the window will generate the corresponding message, then the hook is what meaning, it can monitor a message, such as a window click it, first get the news, but not the application, system, system acquisition the news, go to view this message is a window in which produces, found window, then the message delivery to the corresponding procedures in the message queue, a transfer process, then the hook function is in the message to reach the application before intercepted it, hook can associate a function ( hook processing function ), that is to say, if a process is to install a hook, process and to a corresponding receiving in the news before, will go to perform hook correlation function