Software is ...

• A. A hardware component that powers the system.
• B. A program that enables a controller to function.
• C. A sensor.
• D. A type of communication protocol.

Answer: (B)

Software refers to the set of instructions that run on the controller’s processor to perform its tasks. In a Direct Digital Control system, the hardware provides the computing power and I/O, while the software implements the control logic, data processing, and communication with sensors and actuators. It’s not a physical component that powers the system, nor is it a sensor or a defined method for exchanging data. A sensor is a device that measures a physical quantity, and a protocol is the rules for data exchange between devices. Software enables the controller to function by executing the programmed control routines, monitoring inputs, calculating outputs, and issuing commands to actuators. It can be updated or modified to change how the system behaves without altering the hardware.