<sect1 id="sect-files-overview">
  <title>Files in Gnumeric</title>

<!-- TODO: move the "understanding the filesystem" from 'opening' to here. -->

  <para>
    &gnum; stores its information by creating files and re-opening
    these files during a future session. Saving information to files
    also allows a user to send the information to others.
  </para>

  <para>
    The default file format for &gnum; is based on the eXtensible
    Markup Language (XML). By default, files are saved as text files,
    consisting of XML, which are then compressed using the library of
    the <application>gzip</application> program. The extension for
    &gnum; files is <literal>.gnumeric</literal> on platforms which
    support file extensions of any size, <literal>.gnum</literal> for
    systems which restrict extensions to four letters, or
    <literal>.gnm</literal> for systems which restrict extensions to
    three letters.
  </para>

  <para>
    &gnum; can also open or save files in a number of other file
    formats. The project prides itself for the work reverse
    engineering and supporting the file formats used by Microsoft
    Excel. &gnum; can use the Excel file format as if it were the
    native file format, meaning that &gnum; can store and retrieve
    essentially every aspect of a worksheet using the Excel
    format. Similarly, &gnum; supports the OASIS Open Document Format
    for Office Applications (ODF 1.2) file format (ISO/IEC 26300:2006/Amd
    1:2012) as well as the ECMA 376 2nd Edition file format (ISO/IEC 
    29500:2008) as if they were the native format.
  </para>

  <warning>
    <para>
      &gnum; cannot delete files from the file system. &gnum; can open
      existing files and create new files but cannot delete files once
      they are created. Files can be deleted using a file browser such
      as <application>Nautilus</application> on the GNOME desktop or
      using the command-line program <application>rm</application>.
    </para>
  </warning>

  <note>
    <para>
      This chapter discusses working with actual files. It is also
      possible to import data into &gnum; using the clipboard by
      copying either text or html table information in another program
      and then pasting the resulting data into a worksheet.  See <xref
      linkend="sect-movecopy-xclipboard"/> for details.
    </para>
  </note>

  <para>
    Text files are often used to store data, using many different
    systems to structure the data such as using commas, tabs or spaces
    to separate values. &gnum; features a flexible system that enables
    users to define exactly the structure of the text file to be
    imported or exported.
  </para>

  <para>
    &gnum; can be integrated with an email client to allow files to be
    sent directly as attachments to an electronic mail message.
  </para>

  <para>
    &gnum; also features a command-line tool called
    <application>ssconvert</application> to convert files between any
    of the file formats which it supports.
  </para>


</sect1>

       
