<Alan Kay>As Dan Ingalls used to say: "An operating system is just the stuff
left out of the programming language -- if you don't leave it out, then you
don't need the OS".</Alan Kay>

And one of the most critical things left out of most programming languages
is dynamic binding (and often even static linking,) which is why operating
systems commonly provide both capabilities.  In fact, the operating system
is essentially that body of common, shared code that is dynamically
bound/linked to application programs.  Dynamically binding applications to
that common code base is the primary purpose of the OS.

--Alan