OCX
hi,
an OCX is an activex control, so basically a com component, u build an ocx and distribute it, let me give u an example,
u must have used the Internet explorer, now if u want to implement the Internet explorer in your application window, then microsoft has provided the internet explorer functionality in an OCX and using this ocx u can implement the Internet explorer functionality in your application window,
there is a good book on ActiveX controls by Adam Denings Microsoft Press, and developing activex controls can be done with MFC or via ATL.