re: XOR [ was: Linux stifles innovation... ]

From: Jonathan Morton (chromi@cyberspace.org)
Date: Sat Feb 17 2001 - 03:16:51 EST


>> > > > You know XOR is patented (yes, the logical bit operation XOR).

>> > > But wasn't that Xerox that had that?

>> > US Patent #4,197,590 held by NuGraphics, Inc.

>> The patent was for using the technique of using XOR for dragging/moving
>> parts of a graphics image without erasing other parts. Also, since the
>> patent was granted in 1980, the inventors have had their 17 years of patent
>> protection, and we're all free to use the technique - legally!
>
>So you approve of 4,197,590 and think it was an innovative and non obvious
>invention in 1980?

Dunno about that, but I have heard of "clever techniques" using XOR in
graphic sprite manipulation being used in microcomputer games in the
early/mid 80's. No mention of NuGraphics' patent was present - in fact
this code was available in an "Assembly for fun" type book which I still
have a copy of.

The computer on which these techniques was demonstrated was the BBC
Microcomputer, released in 1981 and based on a 2 MHz 6502. Similar
techniques were doubtless used on games for the Apple ][ which was released
several years previously using a 1 MHz 6502.

--------------------------------------------------------------
from: Jonathan "Chromatix" Morton
mail: chromi@cyberspace.org (not for attachments)
big-mail: chromatix@penguinpowered.com
uni-mail: j.d.morton@lancaster.ac.uk

The key to knowledge is not to rely on people to teach you it.

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