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From: ark@alice.UucP (Andrew Koenig)
Newsgroups: net.graphics
Subject: Re: XOR cursors
Message-ID: <4576@alice.UUCP>
Date: Sun, 17-Nov-85 15:57:33 EST
Article-I.D.: alice.4576
Posted: Sun Nov 17 15:57:33 1985
Date-Received: Mon, 18-Nov-85 07:42:36 EST
References: <959@turtlevax.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 20

Ken Turkowski says:

> 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.
In general, it IS possible to patent a novel combination of several ideas
that have been around for a while as long as the combination is
not obvious.