For a PLC with 16 inputs and 16 outputs, the labeling for inputs and outputs is from what range?

For a PLC with 16 inputs and 16 outputs, the labeling for inputs and outputs is from what range?

• A. 0-15 inputs, 0-15 outputs
• B. 1-16 inputs, 1-16 outputs
• C. 0-16 inputs, 0-16 outputs
• D. 1-15 inputs, 1-15 outputs

Answer: (A)

The labeling uses zero-based indexing. With 16 inputs, the first input is addressed as 0 and the last as 15, giving a range of 0 through 15. The same applies to the 16 outputs. This mirrors how digital I/O is typically mapped in PLCs, where each channel is a distinct position in a set of bits, starting at zero. So 0–15 for inputs and 0–15 for outputs is the correct convention. Using a 1–16 range would imply a different, human-friendly numbering not aligned to the actual hardware addresses, and ranges like 0–16 or 1–15 would either add an extra non-existent channel or omit a real channel.

The labeling uses zero-based indexing. With 16 inputs, the first input is addressed as 0 and the last as 15, giving a range of 0 through 15. The same applies to the 16 outputs. This mirrors how digital I/O is typically mapped in PLCs, where each channel is a distinct position in a set of bits, starting at zero. So 0–15 for inputs and 0–15 for outputs is the correct convention. Using a 1–16 range would imply a different, human-friendly numbering not aligned to the actual hardware addresses, and ranges like 0–16 or 1–15 would either add an extra non-existent channel or omit a real channel.