Picture of pocket abacus
The abacus is a calculation tool that works by sliding beads along columns to represent numbers and to compute arithmetic. Almost any sliding tool used to record calculations can be called an abacus, and over the years there has been many iterations and adaptations of this classic calculator.

For centuries the abacus ruled as the calculator for traders and merchants the world over. Today, much of the world now embraces new technology and the once mighty abacus has been replaced with solar-powered calculators and excel spreadsheets. Yet in some places, the abacus is still used as a learning tool for elementary school students and as a method of calculation for traders.

Though many cultures have used the abacus throughout the years, the two most common types that exist today are the Japanese abacus (called soroban) and the Chinese abacus (called suanpan). The main difference between the two is the Japanese abacus has one row of beads on the top deck where the Chinese has two rows, allowing the suanpan to compute to hexadecimal.
This abacus is modeled after the suanpan.
If you're in the mood to nerd it up, check out some of the other types of abaci used over the years.

The simplicity of this 'computer' belies the complexity of computations achievable. Word on the street is there are techniques to solve for square and even cube root using the abacus!
(this instructable also covers elementary arithmetic, jump to step 7 to see.)

This instructable is entered in the Dadcando Family Fun Contest
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enough talk, let's abacus!
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mutto3 years ago
thank you vwry much it was very easy to learn........very helpful..... i was searching his kind of hepl for many days
rotarygap4 years ago
What is the plural of abacus?
mikeasaurus (author)  rotarygap4 years ago
I prefer abaci. It has a certain je nais quois.
On dit "Je ne sais quoi" :P
Terivia4 years ago
X-mas gift for my Dad!!, don't tell him though.
Greth2064 years ago
Would it be possible to use heavy string/shoelace instead of wire; and string it through, tennis racket style?
mikeasaurus (author)  Greth2064 years ago
Consider that continuous use will cause friction wear on fabric, but it should work. try it out and let me know!
Anthony3124 years ago
I can imagine walking up to one of my nerdy friends and say,
"You've got a pocket calculator? WELL I HAVE A POCKET ABACUS!!! You just got served."
0jack4 years ago
This is awesome. I have a brass pocket-sized abacus, but I never knew what to do with it. This is a great idea, though

Somehow, I'll figure out how to make this into a baby toy (maybe by altering those pop-chain beads)... since the two geekiest people I know are having a baby. I'm smart, I'll work it out.
White_Wolf4 years ago
Thank you!
For years I've wondered how this thing worked. Never got around to looking it up online. Never dawned on me that it was like counting in binary numbers. I do that all the time. Like the words....
Thank you!
In binary would look like this.
01010100 01101000 01100001 01101110
01101011 00100000 01111001 011 01111
01110101 00100001 00000000 00000000

you might want to add the youtube videos of people setting records with these!
This is calculator of future :) .
Wasagi5 years ago
Waaaaaaaaaaay cooler than carrying a calculator. Nice!!
jolshefsky5 years ago
In step 7, 218.25 is represented on the bottom and the sum, 248.37 is on the top. I think you meant for the images to be swapped so the addition looks right. I read a short book on abacus operation and you might want to mention that digit-wise operations are often learned through rote memorization. For instance, 3+4 is a matter of two quick flicks that yield the result 7. You can increment by 1's to accomplish the same thing, but you'll learn to memorize quick enough.
mikeasaurus (author)  jolshefsky5 years ago
step 7 image fixed, thanks for the heads up! Like many things, memorization and repetition are the keys to success. Good tip!
might be a good idea to include a slider to keep track of the decimal point. Still an excellent 'ible.
mikeasaurus (author)  bythenumbers5 years ago
agreed, already noted in Step 1 "The decimal location is defined by use, or can be marked on the frame (a low-tech option would be an elastic around the frame to indicate your decimal)."
nickodemus5 years ago
The ancient version of the calculator watch :D
kcls5 years ago
Cool idea! Great job!