10.6 Why does the <Backspace> key invoke help?

The <Backspace> key (on most keyboards) generates ASCII code 8. C-h sends the same code. In Emacs by default C-h invokes help-command. This is intended to be easy to remember since the first letter of ‘help’ is ‘h’. The easiest solution to this problem is to use C-h (and <Backspace>) for help and <DEL> (the <Delete> key) for deleting the previous character.

For many people this solution may be problematic:

• They normally use <Backspace> outside of Emacs for deleting the previous character. This can be solved by making <DEL> the command for deleting the previous character outside of Emacs. On many Unix systems, this command will remap <DEL>:

            stty erase `^?'
  

• The user may prefer the <Backspace> key for deleting the previous character because it is more conveniently located on their keyboard or because they don't even have a separate <Delete> key. In this case, the <Backspace> key should be made to behave like <Delete>. There are several methods.
  • Some terminals (e.g., VT3## terminals) and terminal emulators (e.g., TeraTerm) allow the character generated by the <Backspace> key to be changed from a setup menu.
  • You may be able to get a keyboard that is completely programmable, or a terminal emulator that supports remapping of any key to any other key.
  • With Emacs 21.1 and later, you can control the effect of the <Backspace> and <Delete> keys, on both dumb terminals and a windowed displays, by customizing the option normal-erase-is-backspace-mode, or by invoking M-x normal-erase-is-backspace. See the documentation of these symbols (see Emacs Lisp documentation) for more info.
  • It is possible to swap the <Backspace> and <DEL> keys inside Emacs:

                   (keyboard-translate ?\C-h ?\C-?)
    

    This is the recommended method of forcing <Backspace> to act as <DEL>, because it works even in modes which bind <DEL> to something other than delete-backward-char.

    Similarly, you could remap <DEL> to act as C-d, which by default deletes forward:

                   (keyboard-translate ?\C-? ?\C-d)
    

    See Swapping keys, for further details about keyboard-translate.

  • Another approach is to switch key bindings and put help on C-x h instead:

                   (global-set-key "\C-h" 'delete-backward-char)
    
                   ;; overrides mark-whole-buffer
                   (global-set-key "\C-xh" 'help-command)
    

    This method is not recommended, though: it only solves the problem for those modes which bind <DEL> to delete-backward-char. Modes which bind <DEL> to something else, such as view-mode, will not work as you expect when you press the <Backspace> key. For this reason, we recommend the keyboard-translate method, shown above.

    Other popular key bindings for help are M-? and C-x ?.

  Don't try to bind <DEL> to help-command, because there are many modes that have local bindings of <DEL> that will interfere.

When Emacs 21 or later runs on a windowed display, it binds the <Delete> key to a command which deletes the character at point, to make Emacs more consistent with keyboard operation on these systems.

For more information about troubleshooting this problem, see If <DEL> Fails to Delete.