test unique prefix.
You may use two hyphens instead of one.  You may separate an option
name and its value with white space instead of an equals sign.

<A NAME="description">&nbsp;</A>
<H2>DESCRIPTION</H2>

<p>This program is part of <a href="index.html">Netpbm</a>.

<p><b>pamtopfm</b> reads a Netpbm image (PNM or PAM) and converts it
to a PFM (Portable Float Map) image.

<p>The PFM (Portable Float Map) image format is a lot like PPM, but uses
floating point numbers with no maxval to achieve a High Dynamic 