Which statement best describes logical addressing in PLCs?

• A. Logical addressing uses the actual hardware addresses on I/O modules.
• B. Logical addressing uses tag-based names that are independent of hardware configuration.
• C. Logical addressing uses a fixed memory map.
• D. Logical addressing requires direct wiring.

Answer: (B)

Logical addressing in PLCs means the program uses tag-based names for inputs, outputs, and variables that are independent of the physical hardware layout. The PLC maintains a tag database and maps each tag to the corresponding hardware address, so the code remains readable and portable even if I/O wiring changes. This decoupling from hardware configuration is what makes tag-based addressing flexible and scalable.

So, using tag-based names that are independent of hardware configuration is the best description. It contrasts with referring to actual hardware addresses, a fixed memory map, or direct wiring, all of which tie the program to specific physical or internal layouts.