//procedure of thwe window being destoryed after the window is removed from the screen.
PostQuit Message(0);
//The post Quitmessage function indicates to the  system that a thread has made a request to terminate .
(quit)
//a specities an application exit code. this value is used as the wparam parameter of the wm_QUIT message
//it causes the get message function to return zero 
break;
default;
return DefwindowProc(hwnd,msg,wParam,lParam);
//The DefwindowProc function calls the default window procedure to provide default processing for any window
//message that an application does not process.
The return value is the result of the message processing 
}
return(0);
}