BPSC Tre 4.0 Computer Science MCQ | Demultiplexer(DEMUX)_Digital Logic

Demultiplexer(DEMUX)_Digital Logic MCQ

A demultiplexer is a combinational digital logic circuit that routes a single input to one of several outputs based on select lines.

1. A demultiplexer is also known as:

A. Data selector
B. Data distributor
C. Encoder
D. Decoder
Answer: B. Data distributor
Explanation: DEMUX distributes one input to one of many outputs, so it’s called a data distributor.

2. A demultiplexer has:

A. Many inputs and one output
B. One input and many outputs
C. Many inputs and many outputs
D. One input and one output
Answer: B

3. DEMUX is a:

A. Sequential circuit
B. Memory device
C. Combinational circuit
D. Clocked circuit
Answer: C
Explanation: DEMUX output depends only on current input and select lines, not past values.

4. A 1:4 demultiplexer has:

A. 4 inputs and 1 output
B. 1 input and 4 outputs
C. 2 inputs and 2 outputs
D. 4 inputs and 2 outputs
Answer: B

5. Number of select lines required for a 1:8 DEMUX is:

A. 1
B. 2
C. 3
D. 8
Answer: C
Explanation:

$$\text{Select lines}={\log }_2(\text{outputs})={\log }_2(8)=3\mathrm{<br>}\mathrm{<br>}\mathrm{<br>}\mathrm{<br><br>}$$

6. A demultiplexer with 4 select lines will have:

A. 4 outputs
B. 8 outputs
C. 16 outputs
D. 32 outputs
Answer: C

7. The output of a DEMUX depends on:

A. Input only
B. Select lines only
C. Input and select lines
D. Clock signal
Answer: C

8. In a 1:4 DEMUX, if select lines are S1S0 = 01, which output is selected?

A. Y0
B. Y1
C. Y2
D. Y3
Answer: B
Explanation: Binary 01 = 1, so output Y1 is activated.

9. If the input of a DEMUX is 0, then:

A. All outputs are 1
B. All outputs are 0
C. Selected output is 1
D. Depends on select lines
Answer: B
Explanation: Input = 0 → no output line can receive logic 1.

10. In a DEMUX, only:

A. All outputs are active simultaneously
B. One output is active at a time
C. Two outputs are active
D. No output is active
Answer: B

11. Which logic gates are mainly used to implement DEMUX?

A. OR gates only
B. AND and NOT gates
C. XOR gates
D. NAND only
Answer: B
Explanation:
AND → to enable selected output
NOT → to complement select lines

12. DEMUX performs the reverse operation of:

A. Encoder
B. Decoder
C. Multiplexer
D. Comparator
Answer: C

13. A decoder can act as a DEMUX when:

A. Enable input is removed
B. Input is used as enable
C. Output is feedback
D. Clock is applied
Answer: B
Explanation: Using input data as enable, a decoder behaves like a DEMUX.

14. DEMUX is used for:

A. Serial to parallel conversion
B. Data distribution
C. Memory addressing
D. All of the above
Answer: D

15. DEMUX is commonly used in:

A. CPU registers
B. Communication systems
C. ALU
D. Flip-flops
Answer: B

16. A 1:16 demultiplexer requires how many select lines?

A. 2
B. 3
C. 4
D. 5
Answer: C

17. If all select lines of a DEMUX are 0, then which output is selected?

A. Last output
B. Middle output
C. Y0
D. None
Answer: C

18. DEMUX has:

A. Multiple inputs and outputs
B. One data input
C. No select lines
D. Memory element
Answer: B

19. DEMUX is a memory device.

A. True
B. False
Answer: B (False)

20. DEMUX requires a clock signal to operate.

A. True
B. False
Answer: B (False)

21. Which statement is TRUE?

A. MUX distributes data
B. DEMUX selects data
C. DEMUX distributes data
D. MUX has multiple outputs
Answer: C

22. DEMUX is mainly used to:

A. Combine data
B. Select data
C. Route data to one destination
D. Route data to multiple destinations
Answer: D