This is the question set along with answers of Digital System Fall 2017, which was taken by Pokhara University.

**POKHARA UNIVERSITY – Digital System Fall 2017**

Level: Bachelor Semester: Spring Year:2017

Program: BBA/BBA-BI/BCIS/BHCM/BBA-TT Full Marks: 100

Course: Digital System Pass Marks: 45

Time: 3 hrs

**Section “A”**

Very Short Answer Questions

Attempt all the questions. 10×2

1. Define the parity bit.

2. Define algorithm for state reduction method of a sequential circuit.

3. Draw the block diagram of a combinational and sequential circuit.

4. Can you realize a 2-input NOR using 2 input NAND gates only.

5. Define K-map.

6. What are the two main functions of the registers? Explain.

7. If there are 235 outputs in demultiplexer, find a number of selection lines

and input lines.

8. Define flip-flop.

9. Find the base x if (211) x = (152) 8 .

10. Represent (-39) 10 into sign-magnitude, 1’s complement and 2’s

complement form.

**Section “B”**

**Descriptive Answer Questions**

Attempt **any six** questions

11. Perform the following calculations

a) (110- 11011) 2 using 1’s and 2’s complement system.

b) (345-67) 10 using 9’s and 10’s complement system.

12. Define logic gates. Explain about 7 different types of logic gates along with Boolean expression, logic symbol, truth table.

13. Differentiate between combinational and sequential circuit. Also explain about characteristics and excitation table of the JK flip flop.

14. Define decoder. Construct a full adder using a 3 x 8 decoder and explain.

15. What is a multiplexer? Realize a full adder using MUX and explain.

16. What do you mean by ripple counter? Draw the circuit diagram of 4-bit ripple counter and explain its working principle along with the timing diagram.

17. Explain the importance of registers and explain briefly about the 4 bit 2 serial-in-parallel out shift registers with the help of a timing diagram.

**Case Analysis**

18. Design a BCD to seven- segment display circuit.

19. a) Define ALU. Explain about 4 bit ALU.

b) What do you mean by edge-triggered flip flop? Explain.

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