Editing Automation (section)

===Computer control===
Computers can perform both sequential control and feedback control, and typically a single computer will do both in an industrial application. [[Programmable logic controller]]s (PLCs) are a type of special-purpose [[microprocessor]] that replaced many hardware components such as timers and drum sequencers used in relay logic–type systems. General-purpose process control computers have increasingly replaced stand-alone controllers, with a single computer able to perform the operations of hundreds of controllers. Process control computers can process data from a network of PLCs, instruments, and controllers to implement typical (such as PID) control of many individual variables or, in some cases, to implement complex control [[algorithm]]s using multiple inputs and mathematical manipulations. They can also analyze data and create real-time graphical displays for operators and run reports for operators, engineers, and management.

Control of an [[automated teller machine]] (ATM) is an example of an interactive process in which a computer will perform a logic-derived response to a user selection based on information retrieved from a networked database. The ATM process has similarities with other online transaction processes. The different logical responses are called ''scenarios''. Such processes are typically designed with the aid of [[use case]]s and [[flowchart]]s, which guide the writing of the software code. The earliest feedback control mechanism was the water clock invented by Greek engineer Ctesibius (285–222 BC).