Which ancient device functioned as a calculator?

• A. Quipu
• B. Astrolabe
• C. Napier's bones
• D. Abacus

Answer: (D)

An abacus functions as a calculator by letting you perform arithmetic through the movement of beads on rods. Each rod represents a place value, and moving beads up or down encodes numbers and carries out operations like addition, subtraction, multiplication, and division. It’s a hand-operated system designed specifically to simplify arithmetic, long before digital devices existed.

Napier's bones are a multiplication aid that uses a set of rods with numbers to simplify products, but they aren’t a general-purpose calculator in daily use. The astrolabe is for measuring celestial positions and solving astronomical problems, not arithmetic. Quipu uses knots on cords to record numerical data, serving as a data-keeping method rather than performing calculations. So the abacus best fits the role of a calculator.