Every process plant has real-time controllers, I/O, field devices, and one or more human machine interface (HMI) applications. Common field devices include instruments, analyzers and valves.
In addition to HMIs, other typical process plant software applications include database and historian, asset management, alarm and event handling, data analysis, enterprise resource planning, simulation, non-linear loop tuning, plant performance monitoring and specialized vertical market process control packages — such as distillation column control. Large process plants often have many of these applications, typically purchased from a wide variety of vendors.