Early Chinese calculating involved two methods: the abacus, a device with movable counters, and counting rods, short, flat sticks arranged to form numerals. Various forms of abacus are found worldwide, suggesting multiple independent inventions, and the Chinese abacus may have been imported from an external source. The original Chinese abacus was a board with loose multicolored counters; the modern version uses beads guided by wires. The counting rods were unique to China and may represent the world’s earliest knowledge-based calculation. Simple arithmetic was performed on the counting rods directly because they displayed numbers with the quantity and arrangement of their elements. More complex operations involved laying down the sticks needed to represent the numbers in a calculation on different rows, leaving a space between them for the interim calculation. The earliest known counting board comes from Greece and is dated to 300 BCE; the earliest counting rods are from 100 BCE, but they are depicted on coins and pottery dated to the fourth century BCE, suggesting that they may be the older device. Both devices show signs of an even earlier origin, though the evidence is inconclusive.