The Run mode is used to execute the user program. Which option best describes this function?

• A. Run
• B. Stop
• C. Program
• D. Test

Answer: (A)

Run mode is the operating state where the PLC actually executes the user program. In this mode the controller continuously performs a scan cycle: it reads the current inputs, processes the program logic, and updates the outputs accordingly. This is when the control system actively responds to sensor changes and drives actuators, turning the programmed instructions into real-world actions.

Stopping halts execution, so outputs aren’t driven by the program. Programming mode is for editing or downloading a new program without running it. Test mode is for debugging or simulation, allowing you to monitor or force signals without affecting the actual process. Because Run mode is the state that physically runs the user program and drives outputs, it best describes this function.