Abacus is the oldest computing device that uses beads . The cocoons are placed on a frame and attached to the wire. Abacus is still used in many parts of the world. It is unknown at this time what he will do after leaving the post. However, many believe that abacus was introduced in China around 500 BC. This instrument was also used in ancient Greece. Although the abacus is believed to have been first introduced in China , it was not widely used in China until the thirteenth century. It was introduced in Japan in the fifteenth century, and a modified version was used in the nineteenth century. In China the abacus is called Suan-pan, in Japan it is called Soroban, and in Russia it is called Sketia .