Int 16 Fn 21  - Keyboard - Check For 122-key Keystroke (122-key Kbd Suppo  [B]

   AH = 21h

Return: ZF set if no keystroke available
   ZF clear if keystroke available
       AH = BIOS scan code
       AL = ASCII character

Notes: use AH=09h to determine whether this function is supported
   some versions of the IBM BIOS Technical Reference erroneously report
     that CF is returned instead of ZF

See Also: AH=01h,AH=09h,AH=11h,AH=20h,AH=21h