"I have a couple old slide rules.  I also have a couple copies of Isaac Asimov's An Easy Introduction to the Slide Rule.  I could still probably figure out how to do trig functions on one if I had to.Back in college, I had a professor that had a rule.  If we wanted to use a calculator, we had to clear all the programs out of it in front of a proctor before the class.  I showed up with a slide rule and a basic 4-function calculator.  I got a nice wink and a nod from him later.  "