Function 47h            Get Current Directory (GETDIR)

    Returns the full path of the current directory on the specified
    drive.

        Entry   AH    = 47h
                DL    = Drive number (0 = default, 1 = A, etc.)
                DS:SI = Pointer to a 64-byte buffer

        Return  Buffer filled
                AX changed
                or
                AX = Error code, if CF is set
                     | 0Fh Invalid drive

    ──────────────────────────────────────────────────────────────────

    This function returns the full pathname of the current directory,
    excluding the drive designator and initial backslash character, as
    an ASCIIZ string at the memory buffer pointed to by DS:SI.

    The pathname may be as long as 63 bytes (without the initial
    backslash), plus the terminating zero byte. If the current
    directory is the root, the function returns a null ASCIIZ string
    (that is, the first byte of the buffer will be zero).