The Abacus (which appeared in the sixteenth century) was the first calculator. 
In the middle of the seventeenth century Blaise Pascal, a French mathematician,
 built and sold gear-driven mechanical machines which performed whole number addition
  and subtraction.  (Yes, the language Pascal is named for him.)
Later in the seventeenth century a German mathematician Gottfried Wilhelm von
 Leibniz built the first mechanical device designed to do all four whole number 
 operations: addition, subtraction, multiplication and division.  
 The state of mechanical gears and levers at that time was such that the Leibniz machine was not very reliable.
