Mechanical Calculator

Published by patrick honner on

Curta calculatorThis videos demonstrates the absolutely amazing Curta Mechanical Calculator.

Invented in the 1940s, this is an entirely mechanical multiplication device.  To operate it, you set the sliders on the side to the first number, and then turn the crank on top an appropriate number of times to multiply by the second number.  Because of it’s obvious resemblance, this is affectionately known as the pepper-grinder calculator.

In the video, the narrator takes his Curta apart and explains a bit of the inner-workings of the device.

If they don’t have one already, the Calculator Museum should definitely make acquiring a Curta a top priority!

Thanks to Ivan for showing me this!

patrick honner

Math teacher in Brooklyn, New York


Ben · January 18, 2011 at 11:11 am

I met one of these calculators in person last week! I did a short internship at an IT company that has a collection of antique computers, and I got to try this one out.

MrHonner · January 18, 2011 at 11:17 am

How efficient is its algorithm?

    Ben · January 18, 2011 at 11:34 am

    Well, every time you turn the crank you add the numbers on the sliders to whichever number fields are aligned above them. You can multiply by 10 by moving the output fields by one digit and then turning the crank as many times as you have 10s in the number. You can also do things like add 4 10s and then subtract a 1 to multiply by 39 (5 cranks instead of 12). So the complexity of the algorithm to multiply m and n is something like O(sum of digits of m or n)

Chris · January 18, 2011 at 11:19 am

These calculators turn up in William Gibson’s Pattern Recognition – nice to actually see them

Ivan · January 18, 2011 at 8:05 pm

If you don’t mind me asking Ben, what IT Company? I would love to have some time with this calculator.

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