How can a Windows application employ multiple processes?

Question

I'm thinking of Chrome & IE8 as examples of applications which have multiple processes each associated with separate windows (and other things too). How does this work? Specifically focusing on the GUI side - one question I have is does Windows treat a HWND as belonging to a process or can one process arbitrarily interact with any HWND?

Answer 1

How does this work? Specifically focusing on the GUI side - one question I have is does Windows treat a HWND as belonging to a process or can one process arbitrarily interact with any HWND?

Each HWND can be arbitrarily interacted with, mostly. For example, this post shows how to embed notepad into a Windows Forms panel.

That being said, it often causes programs to not function correctly, unless they are designed with this in mind.