Source : Free On-Line Dictionary of Computing

space-cadet keyboard
     
        A now-legendary device used on {MIT} {Lisp} machines, which
        inspired several still-current jargon terms and influenced the
        design of {Emacs}.  It was equipped with no fewer than *seven*
        shift keys: four keys for {bucky bits} ("control", "meta",
        "hyper", and "super") and three like regular shift keys,
        called "shift", "top", and "front".  Many keys had three
        symbols on them: a letter and a symbol on the top, and a Greek
        letter on the front.  For example, the "L" key had an "L" and
        a two-way arrow on the top, and the Greek letter lambda on the
        front.  By pressing this key with the right hand while playing
        an appropriate "chord" with the left hand on the shift keys,
        you could get the following results:
     
         L		lowercase l
     
         shift-L	uppercase L
     
         front-L	lowercase lambda
     
         front-shift-L	uppercase lambda
     
         top-L		two-way arrow
     
        (front and shift are ignored) And of course each of these
        might also be typed with any combination of the control, meta,
        hyper, and super keys.  On this keyboard, you could type over
        8000 different characters!  This allowed the user to type very
        complicated mathematical text, and also to have thousands of
        single-character commands at his disposal.  Many hackers were
        actually willing to memorise the command meanings of that many
        characters if it reduced typing time (this attitude obviously
        shaped the interface of {Emacs}).  Other hackers, however,
        thought that many {bucky bit}s was overkill, and objected that
        such a keyboard can require three or four hands to operate.
     
        See {cokebottle}, {double bucky}, {meta bit}, {quadruple
        bucky}.
     
        Note: early versions of this entry incorrectly identified the
        space-cadet keyboard with the "Knight keyboard".  Though both
        were designed by Tom Knight, the latter term was properly
        applied only to a keyboard used for {ITS} on the {PDP-10} and
        modelled on the Stanford keyboard (as described under {bucky
        bits}).  The true space-cadet keyboard evolved from the Knight
        keyboard.
     
        [{Jargon File}]
     
        (1994-12-05)