What is Emacs?
Emacs is not just an editor. It's an editor construction kit that comes
with a half-finished editor. And that's one of the features that makes it
by far the best text editor in the world. The other feature is that you
program it in Lisp. O.K., so Elisp (Emacs's Lisp) is an antiquated
dynamically scoped Lisp, but it's still a real Lisp with Lisp macros and
all.