<!doctype html public "-//W3C//DTD W3 HTML//EN">
<html><head><style type="text/css"><!--
blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
--></style><title>Re: [Gllug] XOR</title></head><body>
<div>At 18:07 +0100 2004/04/15, Richard Jones wrote:</div>
<blockquote type="cite" cite>On Thu, Apr 15, 2004 at 05:33:17PM +0100,
Andrew Halliwell wrote:<br>
> Even the sinclair zx spectrum has "OVER 1" mode, which
turned on XOR for<br>
> screen writing. (Used in that case for games written in BASIC,
and of<br>
> course, for things like underline, creating umlauts from 2
normal<br>
> characters, u and " iirc, etc)<br>
<br>
There's even a bogus patent on using XOR for cursor drawing IIRC.
See<br>
John Walker's page about bogus patents:<br>
</blockquote>
<blockquote type="cite"
cite>http://www.fourmilab.ch/autofile/www/chapter2_105.html<br>
</blockquote>
<blockquote type="cite" cite>Rich.</blockquote>
<div><br></div>
<div><br></div>
<div>Indeed.</div>
<div><br></div>
<div><font face="Geneva" size="+2"
color="#000000"
>http://en.wikipedia.org/wiki/List_of_notorious_software_patents</font
></div>
<div><br></div>
<div>But it what sense is it bogus?</div>
<div><br></div>
<div><br></div>
<div><font face="Geneva" size="+2"
color="#000000">http://www.wired.com/news/linux/0,1411,61631,00.html</font
></div>
<div><br></div>
<div>"...<font face="Geneva" size="+2"
color="#000000">California-based Cadtrak owns a much-disputed patent
on using a simple mathematical operation, known as XOR, to draw a
cursor over an image on screen."</font></div>
<div><br></div>
<div><font face="Geneva" size="+2"
color="#000000">http://nothings.org/computer/patents.html</font></div>
<div><br></div>
<div>"<font face="Geneva" size="+2" color="#000000">Closely
related is a patent which apparently covers results, not process. The
exclusive-or-cursor patent is a simple example of this. There are a
number of mathematically equivalent ways of expressing the xor
algorithm, but it appears to be widely believed that all of them are
covered by the patent. The patent apparently is understood to cover
the idea of representing an onscreen cursor by complementing each
"visible" pixel of the cursor with the contents of whatever
is on screen.</font>"</div>
<div><br></div>
<div><br></div>
<div>Gordo.</div>
<div><br></div>
<x-sigsep><pre>--
</pre></x-sigsep>
<div>"Think Feynman"/////////<br>
http://pobox.com/~gordo/<br>
gordon.joly@pobox.com///</div>
</body>
</html>