Abacus

An abacus is an old tool used for arithmetic. It is still used in some parts of the world, and it is well suited for use in shops and street markets. Sometimes blind people use an abacus, because they can feel the numbers easily. The most common abacuses work by moving beads on rods.

Abacuses can do addition, subtraction, multiplication, division. They can be used to find the square root of whole numbers. Expert abacus users can sometimes do math faster than basic calculators.

There is a common Chinese abacus. This abacus is split into two kinds of basic rows, the top is for the "5"s, and the bottom is for the "ones". There are one or two beads in the top rows, and four or five beads in the bottom ones. For example, 8 is one bead on top and 3 below, because 5 + 3 = 8. Every column represents a different digit.

Etymology
The use of the word abacus dates from before 1387 AD, when the word was got from Latin to describe a sandboard abacus. The Latin word came from ancient Greek  (abax) which means something without base, or (improperly) any piece of rectangular board or plank.

Both abacuses' and abaci are used as plurals. The user of an abacus is called an abacist (soft or hard 'c').

 Japan 
There is a Japanese version of the abacus called the 'soroban'. It works in essentially the same way.

 Other websites 

 General and historical articles 
 Abacus Photos and Images 
 Abacus
 Roman abacus

 Tutorials 

 Manual de uso del Abaco Japonés Soroban 
 Min Multimedia
 Suan Pan 
 Abacus: Mystery of the Bead - an Abacus Manual

 Abacus curiosities 
 Abacus in various number systems 
 Java applet of Chinese, Japanese and Russian abaci 
 An atomic-scale abacus

 References 

Category:Arithmetics
Category:Mathematical tools