Some of us cantankerous and curmudgeonly lovers of puddlejumpers like to do things the oldfangled way, with those nifty E6B's, a handful of good old dead reckoning and a whole lot of by-the-seat-of-yer-pants pilotage. I've only got a private ticket and haven't flown in a while, but I always LOVED doing all those calculations on the "computer," helped along with a freshly-sharpened number 2 pencil. (^-^)
Specialized version of the sliderule for pilots. It's round and used to compute all manner of pilotage parameters vital to aviating from point A to point B. Now everybody uses GPS and inertial navigation computers. Sic transit gloria mundi.