Int 16h, 02h            Get Shift Status                                  all

    Returns the current keyboard shift status.

        Entry   AH = 02h

        Return  AL = 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

    This shift status byte is obtained from the byte at memory
    location 0040h:0017h.

    See Service 12h to obtain the shift status for the enhanced
    (101/102-key) keyboard.