Define pull-up and pull-down resistors and their roles with digital inputs.

• A. A pull-up resistor ties an input to a high level when not driven; a pull-down ties it to ground; both prevent floating inputs and define a known state.
• B. A pull-up resistor ties an input to ground; a pull-down ties it to high; both prevent floating inputs.
• C. Pull-up/pull-down have no effect on floating inputs.
• D. Pull-up/pull-down are only used in power supply circuits.

Answer: (A)