1. 1000 — Pope Sylvester II introduces the abacus using the Hindu-Arabic numeral system to Europe.

2. Fibonacci presented the first complete European account of Arabic numerals and the Hindu-Arabic numeral system in his Liber Abaci (1202).

3. The Abacus (plural abaci or Abacuses), also called a counting frame, is a calculating tool used in the ancient Near East, Europe, China, and Russia, centuries before the adoption of the written Arabic numeral system