What is a PLC program?

• A. A sequence of hardware components.
• B. A series of instructions that directs the PLC to execute actions.
• C. A diagnostic routine for memory testing.
• D. A single instruction controlling a motor.

Answer: (B)

A PLC program is a set of instructions stored in the PLC that tells it how to act. It reads inputs, applies logic or rules you’ve written, and then updates the outputs to control devices. This description fits because the essence of programming a PLC is providing a sequence of instructions that directs the controller to perform actions, not just arranging hardware or running a single test.

In practice, the program is written in languages like ladder logic or structured text and is executed in a repeated cycle: the PLC reads inputs, evaluates the logic, and then updates outputs accordingly. The other ideas—just a sequence of hardware components, a diagnostic memory test, or a single instruction controlling a motor—don’t capture the ongoing decision-making and control flow that a full program provides.