What is the purpose of a PLC I/O address and how is it assigned?

• A. It defines network topology for PLC
• B. It maps physical inputs and outputs to program tags; assigned by the PLC manufacturer or programming software.
• C. It measures analog sensor values
• D. It stores program memory location

Answer: (B)

The I/O address serves as the link between the physical signals on the machine and the control software. It identifies which actual input or output channel on the PLC hardware corresponds to a given tag or reference in the program, so the PLC can read sensor states and drive actuators correctly. When you configure the project, each physical input or output is mapped to a logical tag in the program, and the I/O address is the address the PLC uses to access that channel during operation. This mapping is typically set up in the PLC hardware configuration—either by the manufacturer or through programming software—so the software knows which terminal or channel corresponds to each tag. In many systems, the hardware defines fixed addresses; in others, you can reassign addresses within the software to suit the wiring or to optimize the control strategy.

The other options aren’t correct because the I/O address isn’t about how devices are connected in a network, it doesn’t measure or interpret sensor values itself, and it isn’t where the program’s memory is stored. It’s specifically the mapping that connects physical I/O channels to the program’s references.