Int 2Fh / B711h         Set True-Name Flag                           DOS 4.0+

    Sets the current program's flag that specifies whether the APPEND
    command converts a filename to a full path when it processes
    system functions such as Open File with Handle (Int 21h/3Dh).

        Entry   AX = 0B711h

        Return  Nothing

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    If the true-name flag is set, APPEND expands filenames that are
    passed to the following functions:

        Open File with Handle   Int 21h function 3Dh
        Get File Attributes     Int 21h function 4300h
        Find First File         Int 21h function 4Eh
        Extended Open/Create    Int 21h function 6Ch

    For each function, the program passes an address to the
    zero-terminated filename and APPEND copies the zero-terminated
    path to the same address. The program making the call must ensure
    that the buffer at the address is large enough to contain the full
    path. The APPEND command resets the true-name flag after expanding
    a filename.