Anyone else was lost with the title asking why a mouse or a keyboard should do math ? I spent to much time to find this about Playstation 2, not about Personal System/2 ports used to connect mouse and keyboard.
To all the downvoters: Just because something is obvious to you doesn't mean that it is obvious to everyone else. Three character abbreviations can make context discovery really difficult as simply plopping the abbreviation into Google will quite often produce mostly unrelated results.