If a character is available, return true. Otherwise, return false. If non-character keyboard events are available before the first valid character, they are discarded and are subsequently unavailable. The character shall be returned by the next execution of KEY.
Use of KEY or KEY? indicates that the application does not wish to process non-character events, so they are discarded, in anticipation of eventually receiving a valid character. Applications wishing to handle non-character events must use EKEY and EKEY?. It is possible to mix uses of KEY?/KEY and EKEY?/EKEY within a single application, but the application must use KEY? and KEY only when it wishes to discard non-character events until a valid character is received.