Returns information about specified properties of a file or of a
  logical unit on which a file might be opened.  The unit need not
  exist, nor need it be connected to a file.  If the unit is
  connected to a file, the inquiry encompasses both the connection
  and the file.  Statement format:

   Inquiring by File:

     INQUIRE (FILE=fi [,ERR=lbl][,IOSTAT=ivar][,DEFAULTFILE=def], flist)

   Inquiring by Unit:

     INQUIRE ([UNIT=]u [,ERR=lbl][,IOSTAT=ivar], flist)

   Inquiring by Output List:

     INQUIRE (IOLENGTH=len) olist

     fi     Is a scalar default character expression
            specifying the name of the file for inquiry.

     lbl    Is the label of the branch target statement
            that receives control if an error occurs.

     var    Is a scalar integer variable that is defined
            as a positive integer if an error occurs and
            zero if no error occurs.

     def    Is a scalar default character expression specifying
            a default file pathname (or file specification) string.

     flist  Is one or more inquiry specifiers. Each specifier
            can appear only once.  Information about the
            individual specifiers is available under the
            subtopic headings listed at the end of this Help
            topic.

     u      Is an integer variable or constant specifying the
            logical unit number of the file, optionally prefaced
            by UNIT=.  UNIT= is required if unit is not the
            first I/O specifier.  The unit does not have to
            exist, nor does it need to be connected to a file.
            If the unit is connected to a file, the inquiry
            encompasses both the connection and the file.

     len    Is a scalar integer variable indicating
            the number of bytes of data that would result from
            using "olist" in an unformatted output statement.

     olist  Is a list of one or more output items.

  FILE=fi, UNIT=u, ERR=lbl, and IOSTAT=var can appear anywhere within
  the parentheses following INQUIRE.  However, if the UNIT keyword is
  omitted, the unit specifier ("u") must be the first parameter in
  the list.

  An INQUIRE statement may be executed before, during, or after the
  connection of a file to a unit.  The values assigned by the
  statement are those that are current when the INQUIRE statement
  executes.

  To get file characteristics, specify the INQUIRE statement after
  opening the file.  (File characteristics are stored in the file
  header.)