steam powered computational machine. It is designed to analyze data and perform complex calculations. The smallest difference engines are the size of a large table, and the largest fill entire buildings.
A Difference Engine, also known as Analytical Engine, is an automatic, mechanical calculator designed to tabulate polynomial functions. Both logarithmic and trigonometric functions can be approximated by polynomials, so a difference engine can compute many useful sets of numbers. These devices control power supplies, plumbing, automations and communications.
The input (programs and data) is provided to the machine via punched cards. For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later.