What does a D flip-flop do?

• A. The output follows the D input
• B. The output is an inverse of the D input
• C. The output holds the previous state
• D. The output is randomized

Answer: (A)

A D flip-flop, also known as a data or delay flip-flop, is a type of digital memory circuit that captures the value of the input (D) at a specific moment determined by a clock signal. When the clock signal transitions (usually from low to high), the flip-flop latches onto the current value of the D input and holds it. Consequently, after the clock edge, the output reflects the D input, thus making the output follow the D input at that particular instance.

Once this value is stored, the flip-flop maintains that output until the next clock event occurs, regardless of any changes to the D input. This characteristic makes the D flip-flop extremely useful in synchronous circuits where it's important to store and synchronize data across different parts of a digital system.