Nasty burns.



The Curta looks like you can grind fresh pepper as well.

quote:

Originally posted by Scoutmaster:
I am looking at an abacus given to me by a friend after his trip to China. He went to a local shop to buy souvenirs, the checkout clerk was using it behind the counter to tally purchases, he bought it for the company accountant (me). I have no clue how to use it.

They are really very simple in concept and easy to learn.
Seeing someone with true mastery of the device use one is something to behold, however.

The following link may help.
Interactive Abacus

Edit: New link is to one in Base 10 - Previous link was to a hexadecimal one

quote:

Originally posted by senza nome:

quote:

Originally posted by flashguy:

quote:

Originally posted by LastCubScout:
Never used one. Don't know how to use an abacus either.

How about Napier's Bones?

I think the most fun I ever had doing calculations was extracting square roots using an old 20-digit Friden® electromechanical machine. Anyone watching the procedure would swear the operator had lost his mind--but it produced accurate 10-digit answers, and fairly quickly.

flashguy

Probably using Newton's method for approximating roots.

I don't think so (don't know "Newton's Method"). It used an algorithm based on the fact that the sum of sequential odd numbers is always a perfect square: 1 is a square; 1 + 3 = 4 is a perfect square; 1 + 3 + 5 = 9 is a perfect square; etc. (There is a very nice graphical explanation as to why this is always true.) The algorithm involved subtracting the sequence of odd numbers from a position in the number until it went negative, restoring it and making some changes to set up for the next position. I analyzed the method one day and discovered that at each step, the remainder to be further processed was exactly the same as that when the method taught in basic Algebra was invoked. Since we had been taught in class that the manual method had been proved to always be correct (to whatever level it was taken), and the mechanical algorithm mimicked the intermediate results of the manual method, I was confident I'd get correct results. It was fascinating to watch someone extracting a root with the mechanical device, though--with subtracting the odd numbers, resetting the last (incorrect) one to the even number less, shifting the carriage one direction and moving the finger to the adjacent column in the opposite direction, plus the ringing of the bell every time the machine went negative--it looked as if the operator had gone crazy.

flashguy

Makes me think of Babbage's Difference Engine, flashguy.

I did know how to use one, but I probably could do only basic math with one now.
My Chemistry teacher in High School taught us how to use one at the beginning of the course in '70.
Calculators weren't available yet.

quote:

Originally posted by Pipe Smoker:
Makes me think of Babbage's Difference Engine, flashguy.

Friden did make a more expensive model that did the algorithm automatically, but I never saw one in operation. I did manage in later years to modify the machine settings on both a Marchant and a Monroe calculator such that the algorithm could be worked on them. (It was difficult on the Marchant.)

I was working with the Friden in a Surveying firm in Detroit, Michigan, and we had to carry our calculations to 8 decimal places; had a huge book of trig tables to 10 places to use.

flashguy

In a word -> YES....

quote:

Originally posted by Steve 22X:
They are really very simple in concept and easy to learn.
Seeing someone with true mastery of the device use one is something to behold, however.

Yes, they are quite simple to use. I used one in high school (1962-1965). I was fortunate to have the log-log-double-trig model, or whatever it was called. I was OK with it, until I went to a Southwest Prep school slide rule contest. The guy from the Houston prep school had one of those simple yellow, metal rules, with a minimum of scales, and he just blew us away with his speed. I think he had his rule lubed up with silicone, or something. He won the prize.