Fun XOR trick: using it to move a cursor across the screen without having to keep a buffer of the contents under the cursor (and putting them back). It didn't

Fun XOR trick: using it to move a cursor across the screen without having to keep a buffer of the contents under the cursor (and putting them back). It didn't always look great, but if you were moving a full-screen crosshair around, it was sufficient. Especially on hardware that was slow to move buffers to and from ram. Unfortunately, using this pure-math technique was also patented until 2007 [0], much to the surprise of my former employer in 1986. Cadtrak had collected from companies like IBM and NEC and made a nice business as a troll. [0] https://patents.google.com/patent/US4197590B1/en https://patents.google.com/patent/US4197590B1/en