INT 62 u - FGDRIVER v3.03 - "FG_INTKEY" - GET KEYSTROKE, NO WAIT
        AX = 0051h
        ES:BX -> variable pointer record (see below)
Return: variables updated
Notes:  For FGDRIVER v1.10, this function was "FG_DRAWMASK" (see AX=001Dh);
          "FG_INTKEY" was AX=006Fh
        If the keyboard buffer is empty, both the ASCII and extended keycodes
          are set to 00h
SeeAlso: AX=000Ah,AX=003Ah,AX=0054h,AX=00ADh,INT 16/AH=01h

Format of variable pointer record:
Offset  Size    Description
 00h    WORD    segment of BYTE buffer for ASCII keycode
 02h    WORD    offset of BYTE buffer for ASCII keycode
 04h    WORD    segment of BYTE buffer for extended keycode
 06h    WORD    offset of BYTE buffer for extended keycode

.