The abacus has been in constant use for over 3,000 years. One can add, subtract, multiply and divide with this simple instrument. It is still in common use in China, Russia and much of the middle East. The Japanese use a similar instrument called a soroban. The soroban uses the same principles as the abacus but there is only one row of beads above the bar and only four below the line.

Why the difference between the simpler soroban and the more cumbersome abacus? In China, a common unit of weight, the kin, is equal to 16 ryo. The abacus can readily be used to calculate kin and ryo, while the soroban cannot.

In the pictures you will note a bar that runs horizontally across the abacus. This is the zero bar. The beads are moved toward or away from this bar. The beads below the bar are worth one while the beads above are worth five. The first column to the far right is the units ( one, two, three etc.). The next one moving left is the tens ( 10, 20, 30, etc.). The next is the hundreds, etc. Note that you could interpret the rightmost column as hundredths if you were calculating, for example, currency.

You should use proper technique with these early computing devices. Use your thumb only for adding bottom beads, and never use it above the bar. Use your forefinger for removing bottom beads and for upper bead manipulation. Efficiency requires practice.

To add two or more numbers one enters the first number into the abacus using the column to the far right. In the upper picture 162 has been entered. Note two beads have been moved up toward the zero bar in the column to the far right. The next column moving to the left has one above the bar and one below the bar. The third column has one bead moved up to toward the bar.

The answer of 162 plus 325 is 487 as shown in the lower abacus. In the column to the far right one adds five by moving one bead above the bar downward. This gives a total count of 7 in the far right hand column. In the second column from the right one adds two beads by moving two beads toward the bar below the bar for a total of 8. In the third column from the right there are already 1 bead. In this example, you would move three beads up toward below the bar.

Subtraction is just the reverse. Multiplication and division can also be done on the abacus but are a bit more complicated. Learning to use the abacus involves more than simply understanding the principles. As you become proficient, you discover recurring patterns that, if properly used, will increase your speed and accuracy.

Learning the abacus teaches children basic arithmetic skills more thoroughly than learning addition and multiplication tables. The abacus is not just a children's toy. It remains a serious business tool in many areas. In 1946, a contest was held in Tokyo that pitted an abacus against an electric calculator. The abacus won handily.