Re: Suggested experimental test

[Alfred M. Szmidt]

   >> Even among the C-LETTER and M-LETTER keys, there are quite a few whose 
   >> meaning have changed during the last 40 years.  I know at least of: 
   >> C-h, C-l, M-g, M-j, M-n, M-o, M-p, M-r and M-s.  That's 9 keys out of 
   >> 52.
   >
   > Please describe those changes one by one.  At least for some of these 
   > keys I'm unaware of any changes in their bindings, so I'm curious what 
   > exactly is considered a "change" in this context.


So 6 keybinding got added, not changed.  Two/Three got semantics
changed slightly.  And an equal amount got rebound to something else.
I don't think this means that they changed that much meaning over the
last 40 years.

Since you mentioned "other" Emacsen....

   C-c: was initially exit-recursive-edit, and was changed to a prefix key 
   for modes in Emacs 16; exit-recursive-edit was then moved to C-M-c

Zmacs / TECO had this unbound.

   C-h: was initially (and in other Emacsen) the same as C-b, and was (very 
   early in the development of GNU Emacs) changed into the help character

Not in TECO or ZMACS; C-h was unbound (though, the key on the keyboard
said help, but it was initiated using TOP-h or some such).

   C-l: was 'recenter' up to and including Emacs 22, then became 
   'recenter-top-bottom', which changes its semantics when is repeated

Same in Zmacs / TECO, ignoring the minor semantical difference.

   C-z: was initially (and in other Emacsen) a prefix character, was at some 
   point bound exit-recursive-edit, then became (in GNU Emacs 1.11) bound to 
   suspend-emacs

C-z has always meant to punt Emacs to the background since the early
days of Emacs.

   M-g: was initially bound to fill-region, was used for facemenu in Emacs 
   19-21, and is used for goto-like commands since Emacs 22

Which is also what TECO and Zmacs had it too (fill-region)...

   M-j: was initially unused, became indent-new-comment-line in Emacs 1.7

M-j was in Zmacs for changing fonts.

   M-n and M-p: were initially unused, became what they are now in Emacs 17

These where normaly mode specific, but generally speaking comment
down/up line.

   M-o: was unused before Emacs 22, was used for facemenu in Emacs
   22-27

Once upon a time, this was "this indentation", i.e. new line but keep
same column.

   M-r: was initially unused, became 'move-to-window-line' in Emacs
   16, then became 'move-to-window-line-top-bottom', which changed its
   semantics when it is repeated

Zmacs / Teco have this as "move to screen edge".

   M-s: was initially unused, became center-line for text-modes in
   Emacs 16, and is used for search-like commands since Emacs 23

Center line in TECO / Zmacs.