INT 16h,  12h (18)       Get Extended Shift Status                       many

    Returns the current keyboard shift status. This service is provided to
    support the enhanced (101/102-key) keyboard.

       On entry:      AH         12h

       Returns:       AL         Shift status
                      AH         Extended shift status

  --------------------------------------------------------------------------

                             Shift Status (AL)

               7 6 5 4 3 2 1 0
               1 . . . . . . .      Insert locked
               . 1 . . . . . .      Caps Lock locked
               . . 1 . . . . .      Num Lock locked
               . . . 1 . . . .      Scroll Lock locked
               . . . . 1 . . .      Alt key is pressed
               . . . . . 1 . .      Ctrl key is pressed
               . . . . . . 1 .      Left Shift key is pressed
               . . . . . . . 1      Right Shift key is pressed


                         Extended Shift Status (AH)

               7 6 5 4 3 2 1 0
               1 . . . . . . .      Sys Req key is pressed
               . 1 . . . . . .      Caps Lock key is pressed
               . . 1 . . . . .      Num Lock key is pressed
               . . . 1 . . . .      Scroll Lock key is pressed
               . . . . 1 . . .      Right Alt key is pressed
               . . . . . 1 . .      Right Ctrl key is is pressed
               . . . . . . 1 .      Left Alt key is pressed
               . . . . . . . 1      Left Ctrl key is pressed

       Notes:         This service is supported only on the AT dated
                      11/15/85 and after, the XT dated 1/10/86 and after,
                      and the XT-286.

                      The shift status byte return in AL is obtained from
                      the byte at memory location 0:0417h. Note that this
                      is the same value that is returned by Service 02h.

                      Note that the Extended Shift Status (value returned
                      in AH) reports if keys are being pressed, not
                      locked.

                      See Service 02h for an equivalent service that works
                      with all keyboards, not supporting the new keys on
                      the enhanced (101/102-key) keyboard.