Function 39h (57)        Create Directory (MKDIR)

    Create a subdirectory.

       On entry:      AH         39h
                      DS:DX      Pointer to directory name to create (ASCIIZ
                                 string)

       Returns:       AX         Error code, if CF set

       Error codes:   3          Path not found
                      5          Access denied, or pathname already exists.

                      Call Function 59h for extended error code information
                      for DOS 3.0 and above.

       Network:       Requires Create access rights

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    Function 39h (MKDIR) creates a subdirectory whose path is specified in
    the ASCIIZ string at address DS:DX; the string length is limited to 64
    characters. If the function is unable to create the directory, it sets
    the Carry Flag and returns an error code in AX.

       Notes:         The directory name may include a drive letter.

                      If any of the parent directories in the path do not
                      exist, the directory is not created.