An abacus is made of rows of beads on metal rods. The abacus was an early form of a calculator. This was invented by the Chinese sometime in the second century B.C.
Some Chinese are so skilled that they can figure out a difficult math problem on an abacus faster that a person using a modern calculator!
photo from: http://www.syssrc.com/html/museum/html/sims/abacus/index.html