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Up: <a href="BFD.html#BFD" accesskey="u" rel="up">BFD</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="LD-Index.html#LD-Index" title="Index" rel="index">Index</a>]</p>
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<a name="How-It-Works_003a-An-Outline-of-BFD"></a>
<h3 class="section">5.1 How It Works: An Outline of BFD</h3>
<a name="index-opening-object-files"></a>

<p>When an object file is opened, BFD subroutines automatically determine
the format of the input object file.  They then build a descriptor in
memory with pointers to routines that will be used to access elements of
the object file&rsquo;s data structures.
</p>
<p>As different information from the object files is required,
BFD reads from different sections of the file and processes them.
For example, a very common operation for the linker is processing symbol
tables.  Each BFD back end provides a routine for converting
between the object file&rsquo;s representation of symbols and an internal
canonical format. When the linker asks for the symbol table of an object
file, it calls through a memory pointer to the routine from the
relevant BFD back end which reads and converts the table into a canonical
form.  The linker then operates upon the canonical form. When the link is
finished and the linker writes the output file&rsquo;s symbol table,
another BFD back end routine is called to take the newly
created symbol table and convert it into the chosen output format.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">&bull; <a href="BFD-information-loss.html#BFD-information-loss" accesskey="1">BFD information loss</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">Information Loss
</td></tr>
<tr><td align="left" valign="top">&bull; <a href="Canonical-format.html#Canonical-format" accesskey="2">Canonical format</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">The BFD	canonical object-file format 
</td></tr>
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