2011-02-25 05:43:29

 Abacus is a manual counting device used for solving arithmetical problems in the days before calculators and computers, consisting of a frame holding parallel rods strung with movable counters. The use of the word abacus dates back to before 1387 when a Middle English work borrowed the word from Latin to describe a sand board abacus.
 Abacus was first used in China about 500 BC. It is used to do math such as addition, subtraction, multiplication, and division. It can also be used to extract square roots and cubic roots. The beads on the abacus are used for numbers. You can slide the beads up and down to show the numbers.
 Abacus is typically made of various types of hardwoods and comes in varying sizes. Its frame has a series of vertical rods on which a number of wooden beads are allowed to slide freely. A horizontal beam separates the frame into two sections, known as the upper deck ("heaven") and the lower deck ("earth"). Each bead in the upper deck has a value of 5, while each bead in the lower deck has a value of 1. Beads are considered counted, when moved towards the beam that separates the two decks.
 Abacus is prepared for use by placing it flat on a table or one's lap and pushing all the beads on both the upper and lower decks away from the beam.
 Proper finger technique is paramount in achieving proficiency on the abacus. With a Chinese abacus, the thumb and the index finger together with the middle finger are used to manipulate the beads. Beads in lower deck are moved up with the thumb and down with the index finger. In certain calculations, the middle finger is used to move beads in the upper deck.
 In 1960s, there were many exercises for finger technique and abacus operation as a whole. The exercise I did most is to work out a sum of consecutive numbers from 1 to 100 (and the sum is 5,050). I also liked playing a "cat-mouse" game on an abacus with a playmate.
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张力平,IT行业资深分析师。Zhang Liping, aka Sevencastles,a senior analyst in IT industry and the owner of Seven Castles,'a Shanghai blog featuring news and views of great interest'.