calculating : Idioms & Phrases

• noun a small machine that is used for mathematical calculations
  calculator.
  

WordNet

• a machine for the mechanical performance of mathematical operations, for the most part invented by Charles Babbage and G. and E. Scheutz. It computes logarithmic and other mathematical tables of a high degree of intricacy, imprinting the results on a leaden plate, from which a stereotype plate is then directly made.

Webster 1913