The difference is that DCS is relatively large, which may include PLC. * * * The same point is that a physical IO actually controls the field devices.

DCS is the abbreviation of Distributed Control System, which is also called distributed control system in domestic automatic control industry. Compared with centralized control system, it is a new computer control system, which is developed and evolved on the basis of centralized control system.

Programmable logic controller (PLC) uses a programmable memory for storing programs, executing user-oriented instructions such as logical operation, sequence control, timing, counting and arithmetic operation, and controlling various types of machinery or production processes through digital or analog input/output.