€How did people keep track of numbers before pen and paper were widely available? How does addition and subtraction work if you don't have a handy written form for your numbers? Say you can't read or write, but you can count - how do you add, subtract, multiply, or divide large numbers? The answer to all these questions is the abacus. So what is an abacus? An abacus is a device used for addition and subtraction, and the related operations of multiplication and division. It does not require the use of pen and paper, and it's good for any base number system. There are two basic forms for the abacus: a specially marked flat surface used with counters (counting table), or a frame with beads strung on wires (bead frame). Although counting tables are obsolete now, they have over 2000 years of documented use. This is of specific value to all parents and private math tutors of children, as well as the children themselves, who attend the abacus math lessons at the two Math Genie schools located in the state of New Jersey in the United States of America€.

€Their earliest form was that of a simple stone slab with incised parallel lines. The lines served to mark the place values. The earliest known counting table is from the island of Salamis in Greece. The latest surviving counting table is from the end of the 16th century and is in a museum at Strasbourg. The only real difference between the early and later forms is the direction of the place value lines horizontal or vertical. The medieval European form is the most well documented, in part because the English Exchequer only stopped using the counting table for tallying tax payments and the like in 1826. These tables were used with counters to represent various values. Small stones, called calculi, were used with counting tables in Greece and Rome, and stamped metal counters, rather like coins, were used with counting tables in Europe and England. Although the idea of doing sums with pencil and paper became widespread around 1600 in Europe, and the counting table became completely obsolete in the first quarter of the 18th century, our word 'counter' as used for 'a flat surface upon which business is transacted' is a direct survival of the medieval counting table€.

€The bead frame form is what most people think of when they hear the word, "abacus". There are 3 main forms of abacus in use today; the Chinese, the Japanese, and the Russian. All are composed of a rectangular frame with beads on vertical wires. The number of wires and beads vary, and there may or may not be a horizontal divider in the frame. It cannot be proven, but the Chinese are often credited with the invention of the abacus. The abacus was a great invention in ancient China and has been called by some Western writers "the earliest calculating machine in the world." The abacus has a long history behind it. It was already mentioned in a book of the Eastern Han Dynasty, namely Supplementary Notes on the Art of Figures written by Xu Yue about the year 190 A. D. Its popularization occurred at the latest during the Song Dynasty (960-1127), when Zhang Zeduan painted his Riverside Scenes at Qingming Festival. In this famous long scroll, an abacus is clearly seen lying beside an account book and doctor's prescriptions on the counter of an apothecary's. The most common Chinese abacus has 13 vertical wires, with 7 beads on each wire. The wires and beads are in a rectangular frame. There is a horizontal divider within the frame so the 7 beads on each wire are separated into 2 beads above the divider (the heaven beads) and 5 beads below the divider, the earth beads€.