## Saturday, 7 February 2015

### Switching Theory and Logic Design viva questions with answers

Switching Theory and Logic Design viva questions with answers

STLD
FIRST MID JNTUH ONLINE BITS

UNIT-1(Number systems and codes)

Note: If you find any discrepancies in answers please discuss with concerned subject faculty and report to me…….

Section-I : choose the correct answer

1. The fraction (0.68)10 is equal to [ ]
a) (0.010101)2 b) (0.101)2 c) (0.10101)2 d) (0.10111)2

2. The Hexadecimal number A0 has the decimal value [ ]
a)80 b) 256 c) 100 d) 160

3. Given two numbers A & B in sign magnitude representation in an eight bit format A=00011110 & B=10011100, A XOR B gives [ ]
a)10000010 b) 00011111 c) 10011101 d) 11100001

4. The value of binary 1111 is [ ]
a) 23-1 b) 24-1 c) 24 d) none of these

5. The minimum number of bits required to represent negative numbers in the range of -1 to -11 using 2’s complement arithmetic is [ ]
(a)2 (b) 3 (c) 4 (d) 5

6. The following code is not a BCD code. [ ]
a)Gray code (b) Xs-3 code (c) 8421 code (d) All of these

7. A 15-bit hamming code requires [ ]
(a)4 parity bits (b) 5 parity bits (c) 15 parity bits (d) 7 parity bits

8.If=5,the base(radix) of the number system is [ ]
a)5 (b) 6 (c) 7 (d) 8

9. The hexadecimal number system is used in digital computers and digital systems to [ ]
(a) Perform arithmetic operations (b) Perform logic operations
(c) Perform arithmetic and logic operations (d) Input binary data into the sys

10. Determine the value of base x if : (211)x = (152)8 [ d]
(a) 2 (b) 10 (c) 8 (d) 7

11. Determine the value of base x, if (193)x = (623)8 [a ]
(a)16 (b)4 (c)2 (d)5

12. Which of the following are called Universal gates [ a]
(a) NAND,NOR (b) AND,OR (c) XOR XNOR (d) OR,XOR

Section-II: Fill in the blanks

18. Cyclic codes are also called ________________codes

19. The basic two types of BCD codes are _______________and________ codes.

20. The distance between code words 10010 & 10101 is ________.

21. Convert the binary code (110110)2 to Gray code 101101

22. Conversion of 0.1289062 decimal number to its hexa equivalent is (0.21)16

23. In b’s complement method, the carry is Ignored and in(b-1)’s complement method the carry is add to the LSD

24. The MSB of a binary number has a weight of 512,the number consists of 10 bits bits.

25. Alpha numeric codes are codes which represent letters of the alphabets and decimal numbers as
a sequence of 0s and 1s.

UNIT-2(Boolean algebra and switching functions)

1.The short hand notation of min term m6 is [ d]
(a) (b) (c) ABC (d) 2. In Boolean algebra A+AB= A

3. Boolean expression xy+yz+ = xy+z on reduction.

4. The given expression Y=A+AB+ABC in SOP form is ABC+A+AB+AC

Unit-3(minimization of switching functions)

1. In K-map each of the cell represents one of the _________ possible products [ a ]
(a)2n (b)2-n (c)n2 (d)All the above

Unit-4(combinational logic designs)

1. The serial adder is a ___________circuit, the parallel adder is a ___________ circuit excluding the registers [d ]
(a)sequential, sequential (b)combinational, sequential
(c)combinational, combinational (d) sequential, combinational

2. Which of the following are called Universal gates a[a ]
(a) NAND,NOR (b) AND,OR (c) XOR XNOR (d) OR,XOR

3. Which of the following circuits can be used as parallel-to-serial converter [c ]
(a)digital counter (b)decoder (c)multiplexer (d)demultiplexer

STLD feb 2012 paper

1. The minimum number of bits required to represent negative numbers in the range of -1 to -11 using 2’s complement arithmetic is [d ]
(a)2 (b) 3 (c) 4 (d) 5

2. The following code is not a BCD code. [ a]
a)Gray code (b) Xs-3 code (c) 8421 code (d) All of these

3. A 15-bit hamming code requires [ a]
(a)4 parity bits (b) 5 parity bits (c) 15 parity bits (d) 7 parity bits

4. The logic expression (A+B)(+) can be implemented by giving the inputs A and B to a two-input [c ]
(a)NOR gate (b) NAND gate (c) X-OR gate (d) X-NOR gate

5. Which of the following Boolean algebraic expressions is incorrect? [ b]
(a)A+B=A+B (b) A+AB=B (c) (A+B)(A+C)=A+BC (d) (A+)(A+B)=A

6. If=5,the base(radix) of the number system is [b ]
a)5 (b) 6 (c) 7 (d) 8

7. The hexadecimal number system is used in digital computers and digital systems to [d ]
(a) Perform arithmetic operations (b) Perform logic operations
(c) Perform arithmetic and logic operations (d) Input binary data into the system.

8. The logic expression A+B can be implemented by giving inputs A and B to a two-input [ c]
(a)NOR gate (b) NAND gate (c) X-OR gate (d) X-NOR gate

9. A gate is enabled when its enable input is at logic 0. The gate is [a ]
(a)NOR (b) AND (c) NAND (d) None of these

10. The output of a logic gate is 1 , when all its inputs are at logic 0.The gate is either [a ]
(a)a NOR or an X-NOR (b) a NAND or an X-OR
(c) an OR or an X-NOR (d) an AND or an X-OR

11. In b’s complement method, the carry is Ignored and in(b-1)’s complement method the carry is add to the LSD

12. The MSB of a binary number has a weight of 512,the number consists of 10 bits

13.Alpha numeric codes are codes which represent letters of the alphabets and decimal numbers as a sequence of 0s and 1s.

14. The interconnection of gates to perform a variety of logical operations is called Logic design

15. The NOR gate can function as a NOT gate if All inputs connected togethor

16. The implicants which will definitely occur in the final expression are calledEssential prime implicants

17. The prime implicant mode of a bunch of 0s is called a False prime implicant

18. Encoding is a process of converting familiar numbers or symbols into a coded format.

19. A decoder with 64 output lines has Six select lines.

20. A decimal – to – BCD encoder is a 10 line to 4 line encoder.