Have there been different types of abaciover the centuries?
Yes, there have been many different types of abaci over the centuries, including the
Roman abaci mentioned above. The first type of abacus came into use in China about
1300 and was called a suanpan. Historians do not agree as to whether it was a Chinese
invention or not; some say it came from Japan via Korea. Although merchants used
this type of abacus for standard addition and subtraction operations, it could also be
used to determine square and cube roots of numbers.
The Japanese abacus, or soroban, was similar to the Chinese abacus, but it elimi-
nated one bead each from the upper and lower deck in each column. Thus, it is more
similar to the Roman abacus. The Russians also have their own version of an abacus; it
uses ten beads on each wire, and a single deck. The separation in the wires is created
by one wire with fewer beads.
How are modern abaci used?
Today’s standard abacus is typically constructed of wood or plastic and varies in size.
Most are about the size of a small laptop computer. The frame of the device has a
series of vertical rods or wires on which a number of wooden beads slide freely. A hori-
zontal beam separates the frame into two sections called the lower and upper decks.
For example, in a Chinese abacus, the lower and upper decks each have 13
columns; the lower deck has five beads per column, while the upper deck has two 349
MATH IN COMPUTING
The beads are arranged in this illustration of an abacus to represent the number 38,704.