What is the recommended practice for naming I/O in ladder logic?

• A. Use generic names like IN1.
• B. Use descriptive names and layer them into symbol tables.
• C. Only use numbers.
• D. Use uppercase acronyms for all names.

Answer: (B)

Using descriptive names and layering them into symbol tables keeps ladder logic readable and maintainable. Descriptive names tell you what an input or output represents in the real system, not just a number, so you can understand the logic at a glance. When those names live in a symbol table, you create a single source of truth that maps each descriptive label to its actual hardware address. This separation means you can swap hardware or rewire without rewriting the logic—update the symbol table, and the rest of the program stays correct. It also makes debugging, documentation, and teamwork much easier, since everyone can read and reference the same meaningful labels.

Generic names, numbers, or cryptic acronyms don’t convey function and quickly become confusing as projects grow or when someone new reviews the code. Descriptive naming with symbol tables provides the clarity and flexibility needed for reliable PLC programming.