The Antikythera calculating mechanism (2nd c. B.C.)
It is the first calculating machine in history. It was used to determine and forecast important astronomical and calendar events.
The Greek Abacus (5th c. B.C.)
Abacus was a wooden tablet with small pebbles used to calculate complex mathematical operations. Such an abacus, based on the acrophonic (Herodian) numeral system (e.g.