The pocket calculator is a very complicated digital system. It is revealing to take apart a modern miniature calculator. In a calculator there is a battery, the tiny readout displays, a few wires from the keyboard, and a printed circuit board with an IC attached. That single IC is most of the digital system we call a calculator and contains an LSI chip that performs the task of thousands of logic gates. The single IC performs the storage, processing and control functions of the calculating system. The keyboard is the input and the displays are the output of the calculator system.