First, the distinction between numerical and analog computers is recalled. Numerical computers perform calculations on numbers. Analog computers use physical phenomena associated with continuous variables. Numerical computers work independently of the problem they are solving. Analog computers, on the other hand, exploit the analogy between a problem that cannot be addressed directly and a physical system that can be measured. Therefore, measuring instruments are used to measure input data and the final result. The problem of generating a function using cams is then considered. A simple but significant example is then given. It involves calculating the length of one leg of a right triangle when the lengths of the hypotenuse and the other leg are known by measurement. An important use of analog computers was in the fire control systems of naval guns. Here it is necessary to perform complex but repetitive calculations quickly, a task at which analog computers excelled during World War II. The chapter ends with a note about spiral cams.