Question 1
In a J-K flipflop, when J = 1 and K = 1, it toggles the flipflop’s state.
TRUE
FALSE

The IIT Madras BS Computer System Design (Computer System Design) Quiz 2 paper sat on 16 Aug 2026, in the May 2026 term: 15 questions for 50 marks in 120 minutes. Every question is below with its answer. Take it as a timed mock test to be marked, or read it through first.
In a J-K flipflop, when J = 1 and K = 1, it toggles the flipflop’s state.
TRUE
FALSE
Correct answer
TRUE
A multiplexer is a digital circuit that selects one of the several input signals and forwards it to a single output line.
TRUE
FALSE
Correct answer
TRUE
In a NAND-based gated D latch, when the write enable input is 0, it denotes the Memory Hold state.
TRUE
FALSE
Correct answer
TRUE
In a positive-edge-triggered D flipflop, if the D input is 1 and the clock signal transitions from low to high, Q output is 1.
TRUE
FALSE
Correct answer
TRUE
Sequential circuits do not utilize feedback loops, while combinational circuits do.
TRUE
FALSE
Correct answer
FALSE
Correct answer: 2
Consider a gated D-Latch constructed using NAND gates. The initial input (at t=0 ns) is D=1, and the write enable (WE) signal is high. The write enable toggles between high and low every 5ns, while the input D changes from 1 to 0 and back to 1 every 8ns. What will be the output Q after 24ns?
Correct answer: 0
Consider the J-K flipflop circuit shown below. Assuming the flipflop is initially set to 1, what will be the output sequence Y for the next four clock pulses?
Correct answer: 1111
Consider the circuit consisting of three D flipflops and one NAND gate as shown below. The initial states are Q1=0, Q2=0, and Q3=0. What is the output after (Q1,Q2,Q3) after 5th clock pulse?
Correct answer: 100
None of these
Correct answer
Correct answer: 2
Correct answer: 2
Choose the correct option:
Correct answer
For the circuit shown in Figure 1, D1 and D2 are positive-edge-triggered D flip-flops with inputs x1 and x2 respectively, and their outputs Q1, Q2 feed into an XOR gate to produce Y . Which of the following correctly gives the Boolean expression for Y and the condition under which Y = 1?
Y = Q1 · Q2; Y = 1 whenever x1 = x2 = 1 at the previous rising edge of CLK
Y = Q1 + Q2; Y = 1 whenever either x1 or x2 was 1 at the previous rising edge of CLK
Correct answer
We want to implement a circuit that outputs the sequence changing from 00 → 11 → 10 → 01 → 00 using J-K flipflops, as shown in the figure below. What should be the values of J1, K1, J2 and K2?
J1=Q2, K1=Q2, J2=1, K2=1
None of these
Correct answer