The Russian abacus (tchoty) is held so that counters move crosswise. It has no crossbar, and all counters in one row have the same value. Most rods have ten counters. An occasional row has fewer, to ...

An abacus is an ancient tool used for counting, consisting of a framed set with rods on which balls or beads are moved. The abacus has been in existence in China since the second century BCE, although ...