calculator

A calculator is a hand-held device for performing calculations. Although modern calculators often incorporate a general purpose computer, the device is designed for performing specific operations, rather than for flexibility. For example, there are graphing calculators which focus on graph-centered math like trigonometry and statistics. Also, modern calculators are more portable than most computers, though some PDAs are comparable in size to handheld calculators.
See more at Wikipedia.org...

n. calculator, small machine that makes computations

(n.)
One who computes or reckons: one who estimates or considers the force and effect of causes, with a view to form a correct estimate of the effects.
  

bitty box