Talk:Controller (computing)/Early shared history from Controller
In control theory, a controller is a device that attempts to control states or outputs of a dynamic system. Generally, this is accomplished using feedback to reject disturbances to the system. This is called closed-loop control. Open-loop control is also used for systems that are sufficiently well characterized to predict what inputs are necessary to achieve the desired states or outputs. E.g. the velocity of a motor may be well characterized for the voltage fed into it, in which case feedback may not be necessary.
In business and administration, the controller is one of the senior-most accountants in a firm or institution.