A DCS system is a plant wide control system that generally includes the Human Machine Interface (HMI) for operators to perform control of the plant.  DCS systems are specifically designed to handle critical control processes.

The DCS system should be able to support multiple redundant CPU's that run control algorithms and programs to monitor and control physical interfaces to the plant process.

Control is shared by multiple, redundant processors that are 'distributed' through-out an industrial Plant.

The following Companies Manufacture DCS systems:

Emerson Process Control

Foxboro

ABB

Siemens 

Yokogawa

Honeywell