The abacus is a calculating tool with two beads above the beam and five below, strung on rods. With rhymed rules, people reckon by moving the beads, in the service of trade and fiscal sums.
Around the Song-Yuan transition the abacus strung on rods reached its standard form. The name "abacus" already appears in the verse and prose of the Yuan.
Cheng Dawei's Systematic Treatise on Arithmetic of the Ming systematically summed up the rhymed rules and methods of the abacus. After that abacus arithmetic spread across the country and east to Japan and Korea.
Abacus Arithmetic is the class in the chapter on Sciences on reckoning with the abacus and its rhymed rules. The abacus, with two beads above the beam and five below, took its standard form around the Song-Yuan transition; Cheng Dawei's Systematic Treatise on Arithmetic in the Ming summed up the rhymed rules and methods, and abacus arithmetic spread across the country and east to Japan and Korea.
