Timeline and the History of Computers: Abacus

It was 500 B.C. when abacus appeared. The abacus was first used by the Babylonians as an aid to simple arithmetic. The abacus in the form we are most familiar with was first used in China in around 1300 A.D.

An abacus is a counting frame, typically wooden with beads sliding on wires. For example, Chinese abacus was first used before the adoption of the ten-digit Arabic numeral system and is still occasionally used by merchants and clerks in China and elsewhere.

The Roman abacus contains seven long and seven shorter rods or bars, the former having four perforated beads running on them and the latter one. The bar marked “1” indicates units, “X” – tens, and so on up to millions. The beads on the shorter bars denote fives, – five units, five tens, etc. The rod “O” and corresponding short rod are for marking ounces; and the short quarter rods for fractions of an ounce. Computations were made with it by means of balls of bone or ivory running on slender bamboo rods, similar to the simpler board, fitted up with beads strung on wires, which has been employed in teaching the rudiments of arithmetic in English schools.

The suan pan of the Chinese closely resembles the Roman abacus in its construction and use. The Chinese abacus is usually around 20 cm (8 in) tall and it comes in various widths depending on application. It usually has more than seven rods. There are two beads on each rod in the upper deck and five beads each in the bottom. The beads are usually round and made of hard wood. The abacus can be reset to the starting position instantly by a quick jerk along the horizontal axis to spin all the beads away from the horizontal beam at the centre. The beads are counted by moving them up or down towards the beam. Chinese abaci can be used for functions other than counting. Unlike the simple counting board used in elementary schools, very efficient suan pan techniques were developed to do multiplication, division, addition, subtraction, square root and cube root operations at high speed.

The beads and rods were often lubricated to ensure speed. When all five beads in the lower deck are moved up, they are reset to the original position, and one bead in the top deck is moved down as a carry. When beads in the upper deck are moved down, they are reset and a bead on the adjacent rod on the left is moved up as a carry. The result of the computation is read off from the beads clustered near the separator beam between the upper and lower deck.

The abacus works as a 5-2-5-2 based number system in which carries and shiftings are similar to the decimal number system. Since each rod represents a digit in a decimal number, the number of rods on the abacus only limits the computation capacity of the abacus. When a mathematician runs out of rods, he simply adds another abacus to the left of the row. In theory, the abacus can be expanded.

10. Answer the questions.

1. When did abacus appear? 2. Who and when used the abacus? 3. What is abacus? 4. What does Roman abacus contain? 5. How computations were made with it? 6. How does Chinese abacus look like? 7. How and where Chinese abaci can be used? 8. Why the beads and rods were often lubricated? 9. What happens when all five beads in the lower deck are moved up? 10. On what number system does abacus work?

11. Are these sentences true or false? If false, give the correct version.

1. The abacus was first used as an aid to simple multiplication and division. 2. The abacus in the standard form was first used in China. 3. An abacus is a counting frame, typically wooden with balls sliding on wires. 4. The suan pan usually has more than eight rods. 5. The beads are usually made of stone. 6. Chinese abacus techniques were developed to do square root and cube root operations. 7. People usually lubricated the beads and rods to ensure speed. 8. The abacus works as a 5-2-2-5 based number system. 9. The number of rods limits the computation capacity of the abacus. 10. The abacus cannot be expanded.

12. Compete the sentences according to the text.

1. ________________ when abacus appeared.

2. An abacus is a ___________, typically wooden with beads _____________.

3. ____________ contains seven long and seven shorter rods or bars.

4. The beads on the shorter bars denote ____________.

5. ____________ balls of bone or ivory running on slender bamboo rods.

6. The suan pan of the Chinese _______________ the Roman abacus in its construction and use.

7. There are two beads on each rod ___________ and five beads each _________.

8. The abacus can be reset to the starting position instantly by a quick jerk ___________.

9. ________ clustered near the separator beam between the upper and lower deck.

10. ________, he simply adds another abacus to the left of the row.

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