AH = 52h
        AL = subfunction
            00h get handle attributes
            01h set handle attributes
               BL = new attribute (see returned AL)
            02h get attribute capability
        DX = handle
Return: AL = attribute (for subfunction 00h)
            00h handle is volatile
            01h handle is nonvolatile
        AL = attribute capability (for subfunction 02h)
            00h only volatile handles supported
            01h both volatile and non-volatile supported
        AH = status
            00h successful
            80h internal error
            81h hardware malfunction
            83h invalid handle
            84h undefined function requested
            8Fh undefined subfunction
            90h undefined attribute type
            91h feature not supported
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