file is a named entry in a file system, having an
filename is a handle, not necessarily ever directly represented as an
object, that can be used to refer to a file in a file system (file)
truename tries to find the file indicated by filespec and
returns its truename. If the filespec designator is an open
stream, its associated file is used.
a pathname designator. If filespec is a pathname it represents the name used to open the file
a physical pathname