Control by means of systems that include both digital and analog devices working together to enhance the controller's functionality. As computers and their associated memory have become cheaper, faster, and easier to use, engineers have used them to expand the capabilities of control systems. Most controllers built today are, to some extent, hybrids because digital implementation is usually cheaper and more reliable than analog. The computer in the controller can then be used easily to provide additional capability, such as better response to internal failures. However, the potential benefits of control systems combining the symbol manipulation and decision-making capability of the computer with the precise tracking capability of analog controllers are much greater.