30.5 Keyboard Translations

Some keyboards do not make it convenient to send all the special characters that Emacs uses. The most common problem case is the <DEL> character. Some keyboards provide no convenient way to type this very important character—usually because they were designed to expect the character C-h to be used for deletion. On these keyboards, if you press the key normally used for deletion, Emacs handles the C-h as a prefix character and offers you a list of help options, which is not what you want.

You can work around this problem within Emacs by setting up keyboard translations to turn C-h into <DEL> and <DEL> into C-h, as follows:

     ;; Translate C-h to <DEL>.
     (keyboard-translate ?\C-h ?\C-?)
     
     ;; Translate <DEL> to C-h.
     (keyboard-translate ?\C-? ?\C-h)

Keyboard translations are not the same as key bindings in keymaps (see Keymaps). Emacs contains numerous keymaps that apply in different situations, but there is only one set of keyboard translations, and it applies to every character that Emacs reads from the terminal. Keyboard translations take place at the lowest level of input processing; the keys that are looked up in keymaps contain the characters that result from keyboard translation.

On a window system, the keyboard key named <DELETE> is a function key and is distinct from the ASCII character named <DEL>. See Named ASCII Chars. Keyboard translations affect only ASCII character input, not function keys; thus, the above example used on a window system does not affect the <DELETE> key. However, the translation above isn't necessary on window systems, because Emacs can also distinguish between the <BACKSPACE> key and C-h; and it normally treats <BACKSPACE> as <DEL>.

For full information about how to use keyboard translations, see Translating Input.