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From: ken@turtlevax.UUCP (Ken Turkowski)
Newsgroups: net.graphics
Subject: Re: XOR cursors
Message-ID: <959@turtlevax.UUCP>
Date: Fri, 15-Nov-85 19:10:26 EST
Article-I.D.: turtleva.959
Posted: Fri Nov 15 19:10:26 1985
Date-Received: Mon, 18-Nov-85 07:36:04 EST
References: <1858@saber.UUCP>
Reply-To: ken@turtlevax.UUCP (Ken Turkowski)
Distribution: net
Organization: CIMLINC, Inc. @ Menlo Park, CA
Lines: 19

History: CADTRAK of Sunnyvale is asking big bucks to license the
technology that allows non-destructive display of a cursor by means of
exclusive-or.  They have a patent dated around 1980.

Computer science has been around for a long time, longer than computer
graphics.  It seems to me that there is something written somewhere
about the unique property of the exclusive-OR function that if it is
applied twice with the same source and destination, then the
destination is the same as the original.

What difference does it make that the data in this case controls an
electron beam at a specific spatial location?  Would this same patent,
for example, cover the use of exclusive-or for scrambling speech
signals?  The technology is the same, it is just applied to a different
problem.
-- 
Ken Turkowski @ CIMLINC (formerly CADLINC), Menlo Park, CA
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