Mechanical Calculators
1623-1822

• Wilhelm Schickard's machine for automatic addition, subtraction, and partly multiplication in 1623

• Blaise Pascal's addition machine in 1645

• many similar efforts during 1674-1820

• Tomas de Colmar's Arithmometer, the first mass produced calculator in 1820

• Charles Babbage's Difference Engine, for solving mathematical problems including simple differential equations in 1822.