manual computing devices:
To do multiplication with your fingers in binary is very easy: it's just a mixture of addition and bit-shifting. The only real trick is memory: to multiply a×b, you need to remember the binary digits of both x and y,...
Posted on October 12, 2006 10:14 PM • 14 Comments •
There is another way of doing math on your fingers, which gives you a much greater range of numbers, and which makes multiplication particularly easy. It's a bit more work to get used to than the finger abacus, but it...
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Posted on October 11, 2006 4:12 PM • 10 Comments •
Suppose you want to do some math, but you don't have an abacus handy. Oh, the horror! What do you do? No problem! Your hands make a great two-digit soroban-type abacus. The four beads on the lower deck are your...
Posted on October 9, 2006 8:57 PM • 14 Comments •
Doing square root on the abacus is a lot like doing it on paper. The big difference? It's actually easier on the abacus. What I find pretty cool is that I'm a rank beginner at the abacus. I never actually...
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Posted on October 2, 2006 9:47 PM • 7 Comments •
To do a square root on an abacus, you use partitions to do a paper algorithm for square root using the abacus. The catch is that most people don't even remember how to do square roots on paper, if they...
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Posted on September 28, 2006 11:07 AM • 22 Comments •
Now we're going to try something challenging on the abacus: division. Like multiplication, abacus division is close to the way you'd do it on paper. But just like doing paper division is trickier than paper multiplication, abacus division is tricker...
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Posted on September 25, 2006 11:02 AM • 5 Comments •
Once you can add on an abacus, the next thing to learn is multiplication. Like addition, it follows pretty closely on the old pencil-and-paper method. But it's worth taking the time to look closely and see it step by step,...
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Posted on September 21, 2006 7:33 PM • 4 Comments •
If you want to talk about mechanical computing tools, you can't ignore the abacus. It's the oldest computing tool in the world; and it's still very commonly used. It's also about as different from the slide rule as you could...
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Posted on September 19, 2006 3:45 PM • 16 Comments •
Slides rules are actually astonishingly powerful things. The simple slide rule does multiplication and division using the C and D scales; strictly speaking, you can have a basic rule with nothing but C and D. But you almost never see...
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Posted on September 13, 2006 9:04 PM • 4 Comments •
Several people in the geekout thread asked me to explain how a sliderule works, and I've been meaning to write a couple of article about manual computing devices. So I thought I'd do it. There's a nice slide-rule simulator at...
Posted on September 12, 2006 6:30 PM • 25 Comments •
