| |
Think about what happens every time you buy something in a store. The clerk scans the item's barcode into a scanner, and the cash register calculates the totals. Now imagine this: In some stores in China, there are no barcodes or scanners or cash registers. Instead, when it is time to pay, the clerk grabs a wooden tool with beads on rods, and after a series of quick flicks and clicks, tells you the cost of the items. You might ask, "How can clerks know the cost of things just by moving a bunch of beads?" The patient clerk would explain that this counting device is not just a bunch of beads on rods, but one of the earliest known counting devices in history: the abacus.
Making its official debut in China in the 13th century, the abacus continues to help people calculate the costs of the things they buy and sell. As old as it is, the Chinese abacus (or suan pan) is not the earliest hand-held calculator. Merchants in the Roman Empire (around 300 B.C.) developed an abacus that could fit into a shirt pocket. It was made of metal with rows of open slots that held beads inside each slot. The beads could be moved up and down within the slots to make calculations. Each row of slots represented place values (tens, hundreds, etc.), and the beads acted as placeholders. (See the problem below for a drawing of this device.) It is thought that Chinese merchants who traded with the Roman Empire saw these calculators and then created the suan pan.
In the 1600s, a different type of abacus appeared in Russia: the schoty. Instead of moving beads up and down, this device is set up to move beads on rods from side to side. It still uses rows to indicate place values and beads to do the counting, but there is only one set of beads for each place value. These ten beads represent a person's ten fingers. If you place your hands flat on a table, you will see that your thumbs meet in the middle; the two middle beads on a schoty are colored differently to represent your thumbs. (See the problem below for a drawing of this device.) The schoty is still commonly used in Russia today.
While these early counting devices are not as sophisticated as electronic calculators or cash registers, they are much better than counting on your fingers and toes. They also work when the power goes out!
|
