The use of computers to control a process in which analogue signals of measured process variables such as pressure, temperature, level, etc. are converted to a digital signal that is then manipulated according to a model of the process. The digital output from the computer is then converted back to an analogue signal to make the controlled adjustments to the process. The advantage of computer control is that it is able to process large volumes of data at high speed obtained in real time from around the process compared with traditional analogue controllers.