Which of the following statements best defines Digital Signals?

• A. Signals used for computer data and digital audio
• B. Signals used for natural sound and analog measurements
• C. Signals that vary smoothly with time
• D. Signals that carry only DC levels

Answer: (A)

Digital signals encode information with a limited set of discrete levels, typically two (0 and 1), rather than changing smoothly over time. This makes them ideal for carrying computer data and digital audio, because the discrete levels are robust to noise and easy to process with digital electronics. In digital audio, for example, an analog sound wave is sampled and quantized into a finite number of levels, producing a sequence of numbers that represents the sound for storage or transmission and can be accurately reconstructed later.

The other descriptions describe analog behavior. Signals that vary smoothly with time represent continuous changes, not discrete levels. Signals that carry only DC would be constant and do not reflect how digital data is typically transmitted over time.