15.3.58 !keycode

[x11 package] If key press events are selected through xregister and waited for using xloop, then !keycode contains the X key code of the key pressed last. This code refers to a particular physical key on your keyboard, regardless of what character or function that key represents, and regardless of what modifier key or keys (Shift, Ctrl, Alt, Caps Lock, etcetera) are also active. There is no obvious translation from such a key code to the character or function that it represents. Most users will prefer to inspect !keysym instead.

See also: !keystate, !keysym, xloop, xregister