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<section id="runtimeparams">

<title>Changing &TEXMF; run-time parameters</title>

<para>You can control a number of run-time parameters (in particular,
array sizes) on the command-line or in a configuration file.</para>

<para>Some of the more interesting paramaters:</para>

<variablelist>
<varlistentry>
<term>main_memory</term>
<listitem><para>Total words of memory available, for &TeX;, &METAFONT;, and &MetaPost;.
</para></listitem>
</varlistentry>
<varlistentry>
<term>extra_mem_bot</term>
<listitem><para>Extra space for large &TeX; data structures: boxes, glue,
breakpoints, et al.</para></listitem>
</varlistentry>
<varlistentry>
<term>font_mem_size</term>
<listitem><para>Words of font info available for &TeX;.</para></listitem>
</varlistentry>
</variablelist>

<para>See <xref linkend="defaults"/>, for a complete list of the
&TEXMF; run-time parameters.</para>

<para>Here is a typical example of a configuration file:</para>

<indexterm>
<primary>main_memory</primary>
</indexterm>

<indexterm>
<primary>extra_mem_bot</primary>
</indexterm>

<indexterm>
<primary>font_mem_size</primary>
</indexterm>

<programlisting>main_memory=2000000
extra_mem_bot=2000000
font_mem_size=2000000</programlisting>

<para>The name of the configuration file is that of the engine (e.g., &miktexpdftex;)
or format (e.g, &miktexpdflatex;). You use the <option>--edit-config-file</option>
option of &initexmf; to edit the configuration file, e.g.:</para>

<informalexample>
<screen><prompt>&prompt;</prompt><userinput>initexmf --edit-config-file=pdflatex</userinput>

<prompt>&prompt;</prompt></screen>
</informalexample>

</section>
