>>> As I understand it, vi was originally written as a more interactive/nicer
>>> interface to the ed editor.  I believe that we have both ed and ex because
>>> ed is kept minimalist for /bin.  On the other hand, NetBSD's vi is built
>>> on top of ex (or is actually the same binary?).  vi requires shared
>>> libraries, so you don't want that in /bin.  (^&
>
>It is not an interface to ed. It is a complete rewrite from the ground up.

The thing I never understood was ... it always seemed like vi was owned
by USL ... at least it never seemed to be part of BSD source releases.
Am I mis-remembering things?

--Ken