The basic memory element used to build a register is the _____ flip-flop.

The basic memory element used to build a register is the _____ flip-flop.

• A. D flip-flop
• B. JK flip-flop
• C. SR flip-flop
• D. T flip-flop

Answer: (A)

A memory element for a register needs to capture a value cleanly on a clock edge and then hold that value reliably until the next clock. The D flip-flop does exactly this: it has a single data input and a clock input, and on a triggering clock edge the output Q becomes the value present at D, then remains constant until the next edge. This predictable, edge-driven storage is why registers are built from D flip-flops—multiple D flip-flops can be chained to store multiple bits in parallel, forming a parallel data register. The other flip-flops have behaviors that complicate straightforward storage. A SR flip-flop can enter an invalid state if both S and R are asserted; a JK flip-flop can toggle or change state in more complex ways depending on inputs; a T flip-flop toggles the output with each clock, which isn’t suitable for storing a fixed data bit without extra logic. Hence, the D flip-flop is the standard basic memory element used to build registers.

A memory element for a register needs to capture a value cleanly on a clock edge and then hold that value reliably until the next clock. The D flip-flop does exactly this: it has a single data input and a clock input, and on a triggering clock edge the output Q becomes the value present at D, then remains constant until the next edge. This predictable, edge-driven storage is why registers are built from D flip-flops—multiple D flip-flops can be chained to store multiple bits in parallel, forming a parallel data register.

The other flip-flops have behaviors that complicate straightforward storage. A SR flip-flop can enter an invalid state if both S and R are asserted; a JK flip-flop can toggle or change state in more complex ways depending on inputs; a T flip-flop toggles the output with each clock, which isn’t suitable for storing a fixed data bit without extra logic. Hence, the D flip-flop is the standard basic memory element used to build registers.