Re: when rebind a key with global-set-key , if I need to use global-unset-key on that key ?

[Bastien]

waterloo <waterloo2005@gmail.com> writes:

> In `16.9 Loading Files' of Intro to Emacs Lisp  under emacs23.0.96.1 .
> ==================
> To replace the key binding for the default
> `split-window-vertically', you must also unset that key and bind the
> keys to `split-window-quietly', like this:
>
>      (global-unset-key "\C-x2")
>      (global-set-key "\C-x2" 'split-window-quietly)

Try it.  You'll see that (global-set-key "\C-x2" 'split-window-quietly)
is enough.  

> Please note "must" in above paragraph.

Yes.  Perhaps it's legacy from older versions of Emacs.
I don't know how to fix the Emacs Lisp Intro.

-- 
 Bastien