The Abacus and the Soroban

This is a Chinese abacus (Latin meaning "sand tray") or "Saun pan", which means calculating plate, in Chinese. It has two sections of bead separated by a "reckoning bar." The top section is called heaven, and the beads are worth 5. The bottom section is called earth, and the beads are worth one. There are two beads on each rod in the heaven section and five beads each in the earth section. The beads are counted by moving them up or down towards the bar. If you move them toward the beam, you count their value. If you move away, you subtract their value. Addition and subtraction however are not the only things the Chinese do on the abacus. Techniques have been developed to do multiplication, division, addition, subtraction, square root and cube root operations, although I do not know how to do these techniques and they are not necessary for a simple introduction the abacus.

This one is from Japan and is called a "Soroban" or "counting tray." Use of the Chinese abacus spread to Korea, and then to Japan during the latter part of the 15th century. Originally the soroban looked very much like its Chinese cousin having two beads above the reckoning bar and five beads below. Around 1850, it was modified to have only one bead above the reckoning bar while maintaining the five beads below. It was further changed by removing one lower bead in 1930. This one bead above and four beads below, an arrangement which remains to this day. The soroban is still being used in Japanese schools. The beads have retained their same value, but using it is a little different. Also, another unique feature is that it can calculate percentages, or numbers less than 1.

And if you'd like to make one...