   win32 programming : callback
  What are callback functions, how can I use them and for what?thanks. 
  You use them to process WIndows message events. Say you click the mouse - that''s an event. That''s processed inside the callback function. Just follow the tuts on the stuff (theforger has some great stuff) and experiment a little. You''ll start to get the hang of things once you start using them. ;  Callback functions are functions that other objects can call. For example, the window procedure is a callback function - you pass its address to the WNDCLASSEX structure so that when you register that class Windows knows what function to call when it is time to process a message. It calls that function to process that message.   Colin Jeanne | Invader''s Realm