input_file

    Specifies the name of the file to be viewed. If you do not
    specify an input file name, you are prompted for one. You
    cannot use the asterisk (*)  and the percent sign (%) wildcard
    characters in the file specification.

    The default input file format is DDIF, and the default file type
    is DDIF. Valid input file formats are any of those for which
    there is an input converter installed on the system.