Operational Technology (OT) or in the other well-known term called Industrial Control System (ICS) consists of three core entities that build the environment. These core entities are the backbone of any OT/ICS environment to regulate the process, as per the output expectation.

The core entities of an OT/ICS environment are:
1. Process
2. Algorithm
3. Hardware

1. Process
Process variable measurement consists of 5 elements: flow, level, pressure, temperature, and composition.

But it can also have other forms of measurement such as voltage, emission level, rotation speed, frequency, etc. that depend on the critical infrastructure industry being regulated.

2. Algorithm
Referring to IEC 61131-3 (3rd edition), there are 4 programming languages being used in OT/ICS, Ladder Diagram, Function Block Diagram, Structured Text, and Sequential Function Chart.

Nowadays, Function Block Diagram is commonly used as the standard programming language in major DCS/PLC OEM since it has several advantages over the Ladder Diagram.
Some OEMs may have their own proprietary Function Block to optimize the process regulation.

3. Hardware
The hardware of an OT environment consists of core entities: sensing devices, actuating devices, and controller.

Network (field device communication, higher layer network communication – including networking devices and networking security devices) and Operational Management System (HMI, Production Database Server, Engineering Workstation, Historian, System Integration via Application Server, Industrial Security Monitoring – SIEM, etc.) as the essential system to support the integration, operations, and management of an OT environment.