Abacus Abu and the proud computer
Aditya Rishi

A CALCULATOR named Later visits his successor, Mr Processor, the most powerful supercomputer in the world, to see how it is doing. "Hi Processor, how are you doing?" says Later. "I always do better than you," says Mr Processor, "You are way too old for this world; why don't you retire humbly, before I push you out of public memory." Later: "Processor, your rude behaviour does not shock me because I, once, gave the same advice to one of my ancestors, Abacus Abu, who is the ancestor of all calculating machines. It proved me wrong; and it is still more powerful than you." Processor: "Abacus Abu? I have never heard of such a thing. What is that?"

Later: "Abacus Abu, the abacus, is a mechanical aid used for counting; it is not a calculator in the sense we use the word today. The person operating the abacus performs calculations in his or her mind and uses the abacus to keep track of the sums, the carrys, etc. It was devised by ancient merchants, who, for trading goods, not only needed a way to count goods bought and sold, but also required to quickly calculate the costs. Until numbers were invented, these counting devices were used to make everyday calculations. The first counting board probably involved drawing lines in the sand (the space between 2 lines would represent the units 10s, 100s, etc.) and placing small pebbles within those lines, as place holders representing numbers. The need for durability gave way to wooden boards, who gave way to marble and metal tablets. The oldest surviving counting board is the Salamis Tablet, used by the Babylonians close to 300 BC and rediscovered in 1899 on the island of Salamis. It is a slab of marble marked with 2 sets of eleven vertical lines (10 columns), a blank space between these, a horizontal line crossing each set of lines and Greek symbols along the top and the bottom."

"An abacus (picture 1) is a grid divided into two decks — upper and lower — by a horizontal wire running across. The place values, shown on vertical lines running across, increase from right to left. Decimal place values increase from left to right. The upper deck has two beads in each vertical line and the lower deck has five beads in each line. To count one (picture 2), move one bead on the 1's line from the lower deck to the middle bar (deck divider). To count 2, move 2 beads up from this deck. All values are read from the middle bar. After moving 5 beads up (picture 3) from the lower deck, a carry to the upper deck (picture 4) and a reset of the lower deck (picture 5) will complete counting 5.

In actual operation, the fifth bead in the lower deck is never moved, the carry-reset operation is performed in one motion. We discover that every bead in the lower deck symbolises 1 and every bead in the upper deck symbolises 5."

(to be continued; write at The Tribune or adityarishi99@yahoo.co.in)