Exam-style question
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Which of the following is true about a D flip‑flop?.
- A.It stores the value of D on the falling edge of the clock.
- B.It stores the value of D on the rising edge of the clock.
- C.It stores the value of D immediately when D changes.
- D.It ignores the clock signal.
Model answer
What a good answer should say
- It stores the value of D on the rising edge of the clock.
Explanation
Why this works
Rule: A D flip‑flop captures the input D only at the moment of the clock’s rising edge. Substitution: D=1, clock rising.
Working: The output Q becomes 1 only when the clock edge occurs, regardless of subsequent changes to D. Answer: The D flip‑flop stores D on the rising edge.
Conclusion: D flip‑flops are edge‑triggered devices that sample input at clock transitions.
Common mistake
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