Confusion about Undo keybinding

[Kevin Havener]

According to the tutorial and other places, undo is bound by default to
C-/, C-_, and C-x u. However in my newly installed emacs 24.5, C-/ is
bound to DEL (backspace). I don't think I have any .emacs type file
overriding the defaults, so is this wrong or is the documentation wrong?

Wait just a minute. C-/ is bound to undo in graphical mode and in xterm
(-nw) mode. C-/ is bound to DEL in my linux virtual consoles. How is
this possible?

Can you tell me what is going on?

Thank you,
Kevin Havener

[Barry Margolin]

In article <mailman.4403.14552184...@gnu.org>,

Kevin Havener <have...@gmail.com> wrote:

> According to the tutorial and other places, undo is bound by default to
> C-/, C-_, and C-x u. However in my newly installed emacs 24.5, C-/ is
> bound to DEL (backspace). I don't think I have any .emacs type file
> overriding the defaults, so is this wrong or is the documentation wrong?
>
> Wait just a minute. C-/ is bound to undo in graphical mode and in xterm
> (-nw) mode. C-/ is bound to DEL in my linux virtual consoles. How is
> this possible?

In terminal mode, only ASCII characters can be used, and there is no
ASCII C-/ character. When you type C-/ it sends the DEL character, I
think because this is what Teletype terminals in the 70's did (or maybe
it's what DEC VTxxx terminals did).

--
Barry Margolin, bar...@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

[Emanuel Berg]

Kevin Havener <have...@gmail.com> writes:

> I don't think I have any .emacs type file overriding
> the defaults

You can check this with emacs -Q.

> C-/ is bound to undo in graphical mode and in xterm
> (-nw) mode.

I wouldn't call this "xterm mode" as just about any
terminal emulator (urxvt, Gnome terminal, etc.) should
be able to do this.

But actually the Emacs help mentions xterm:

-nw, --no-window-system
Tell Emacs not to create a graphical frame. If you use
this switch when invoking Emacs from an xterm(1) window,
display is done in that window.

> C-/ is bound to DEL in my linux virtual consoles.
> How is this possible?

Here is a tutorial if you want to rebind it:

http://user.it.uu.se/~embe8573/tty-emacs-keys.txt

use, e.g.:

(define-key input-decode-map [?\u0114] [C-/])

> Can you tell me what is going on?

The Linux VTs are not the same as X. xterm may appear
closer to the Linux VTs but it is not: it *is*
"x"term, aye?

PS. I have `undo' M-0 - very fast, close, and
ergonomic if I may... DS.

--
underground experts united
http://user.it.uu.se/~embe8573