External Tags represent the status of which of the following?

External Tags represent the status of which of the following?

• A. Internal PLC operating status.
• B. Memory locations for data.
• C. Instruction timing.
• D. Status of input or output devices connected to the PLC terminals.

Answer: (D)

External Tags are tied directly to the hardware points on the PLC. They reflect the real-time status of input devices (like sensors and switches) and the state of outputs (like coils and actuators) that are connected to the PLC terminals. When a sensor changes state, the corresponding external tag updates to show that new value, and when the program writes to an external tag, it drives the connected output to energize or de-energize accordingly. This direct hardware mapping is what lets the PLC program read what’s happening in the plant and control devices in response. It’s different from internal tags, which are used for data storage and calculations inside the program and don’t necessarily correspond to physical hardware. In practice, you’d see an external tag go true when a switch is pressed or a sensor is triggered, and you’d set an external tag to energize a conveyor motor or indicator light.

External Tags are tied directly to the hardware points on the PLC. They reflect the real-time status of input devices (like sensors and switches) and the state of outputs (like coils and actuators) that are connected to the PLC terminals. When a sensor changes state, the corresponding external tag updates to show that new value, and when the program writes to an external tag, it drives the connected output to energize or de-energize accordingly. This direct hardware mapping is what lets the PLC program read what’s happening in the plant and control devices in response. It’s different from internal tags, which are used for data storage and calculations inside the program and don’t necessarily correspond to physical hardware. In practice, you’d see an external tag go true when a switch is pressed or a sensor is triggered, and you’d set an external tag to energize a conveyor motor or indicator light.