The abacus (plural abaci or abacuses), also called a counting frame, is a calculating tool which has been used since ancient times. It was used in the ancient Near East, Europe, China, and Russia, millennia before the adoption of the Hindu-Arabic numeral system.^[127] The exact origin of the abacus has not yet emerged. It consists of rows of movable beads, or similar objects, strung on a wire. They represent digits. One of the two numbers is set up, and the beads are manipulated to perform an operation such as addition, or even a square or cubic root. The Sumerian abacus appeared between 2700 and 2300 BCE. It held a table of successive columns which delimited the successive orders of magnitude of their sexagesimal (base 60) number system.^[128]