PG 81
Processing the Message
 All the messages that a window procedure chooses not to process only three  msg:WM_CREATE,WM_PAINT,WM_DESTROY.The window procedure is structured like this:
switch (iMsg)
{
Case WM_CREATE:
[Process WM_CREATE message]
return 0;
Case WM_PAINT
[Process WM_PAINT message]
return 0;
Case WM_DESTROY
[Process WM_DESTROY message] 
return 0;
}
return DefWindowproc(hwnd,iMsg,wParam,IParam);
WndProc includes WM_CREATE processing by returning 0 from the window procedure
The second msg that WMProc processes is WM_PAINT it informs a program when a program part or all of the window client area is "invalid" & must be of the "update",which means that it must be re-drawn or"painted".When the window is first created,the entire client area is invalid b'coz the program has not yet drawn anything on the window.When u resize HELLOWIN's window ,the client area becomes invaild you" recall that the style field of  