STLD OBJECTIVE QUESTION 1

 STLD MID I MCQ 

UNIT-I: Review of Number Systems & Codes & Boolean Algebra & Logic Operations

1What is the radix of the hexa decimal number system?

a) 2 b) 8 c) 10 d) 16

Answer: d) 16

2Which code represents each decimal digit with a 4-bit binary code?

a) Gray code b) Excess-3 code c) BCD code d) 2421 code

Answer: c) BCD code

3How is Gray code different from binary code?

a) It uses more bits. b) Adjacent code values differ by only one bit.

c) It is a weighted code. d) It is primarily used for error detection.

Answer: b) Adjacent code values differ by only one bit.

4Which type of parity checking adds a bit to make the total number of 1s even?

a) Odd parity b) Even parity c) Hamming code d) Cyclic Redundancy Check

Answer: b) Even parity

5What is the purpose of Hamming code?

a) Error detection only b) Error correction only 

c) Error detection and correction d) Data compression

Answer: c) Error detection and correction

6Which Boolean theorem states that A+(B+C)=(A+B)+C

a) Commutative Law b) Associative Law c) Distributive Law d) De Morgan's Theorem

Answer: b) Associative Law

7The principle of duality in Boolean algebra involves interchanging which operations and constants?

a) AND and OR, 0s and 1s b) NOT and XOR, As and A's

c) NAND and NOR, inputs and outputs d) SOP and POS forms

Answer: a) AND and OR, 0s and 1s

8According to De Morgan's theorem, (A⋅B)′is equivalent to:

a) A′+B′ b) A′⋅B′ c) A+B d) A⋅B

Answer: a) 𝐴′+𝐵′

9Which of the following is considered a universal logic operation?

a) OR b) AND c) NOT d) NAND

Answer: d) NAND

10What is the standard form that represents a Boolean expression as a sum of product terms?

a) POS b) SOP c) NAND-NAND d) NOR-NOR

Answer: b) SOP

11What is the 1's complement of the binary number 10110?

a) 01001 b) 01010 c) 10101 d) 11001

Answer: a) 01001

12What is the 2's complement of the binary number 10110?

a) 01001 b) 01010 c) 10101 d) 11001

Answer: b) 01010

13The Excess-3 code for decimal digit 5 is:

a) 0101 b) 1000 c) 0010 d) 1011

Answer: b) 1000

14How many bits are required to represent a hexadecimal digit?

a) 2 b) 3 c) 4 d) 8

Answer: c) 4

15If a binary number is converted to Gray code, how many bits differ between adjacent code words?

a) All bits b) Two bits c) One bit d) Zero bits

Answer: c) One bit

16Which code is a self-complementing BCD code?

a) 8421 code b) Gray code c) Excess-3 code d) 2421 code

Answer: c) Excess-3 code

17The expression for De Morgan's theorem for OR operation is:

a) (𝐴+𝐵)′=𝐴′⋅𝐵′ b) (𝐴⋅𝐵)′=𝐴′+𝐵′ c) 𝐴+𝐵=𝐵+𝐴 d) 𝐴⋅(𝐵+𝐶)=𝐴⋅𝐵+𝐴⋅𝐶

Answer: a) (𝐴+𝐵)′=𝐴′⋅𝐵′

18Which logic gate outputs a HIGH only when all inputs are HIGH?

a) OR b) NOR c) AND d) XOR

Answer: c) AND

19Which logic gate is obtained by inverting the output of an OR gate?

a) AND b) NAND c) NOR d) XOR

Answer: c) NOR

20What is the main advantage of using NAND-NAND and NOR-NOR realizations?

a) Reduced complexity of circuits b) Easier to implement universal gates

c) Reduced power consumption d) Fewer gates required compared to other realizations

Answer: d) Fewer gates required compared to other realizations

UNIT-II: Minimization Techniques & Combinational Logic Circuits Design

1What is the maximum number of variables a K-Map can efficiently minimize according to the text?

a) 4 b) 5 c) 6 d) 8

Answer: c) 6

2The Quine-McCluskey method is also known as the:

a) Graphical method b) Tabular method

c) Boolean algebra method d) Karnaugh map method

Answer: b) Tabular method

3A Half Adder circuit is used to add:

a) Three binary bits b) Two binary bits

c) Four binary bits d) Multiple binary numbers

Answer: b) Two binary bits

4How many inputs does a Full Adder take?

a) One b) Two c) Three d) Four

Answer: c) Three

5Which circuit is used to find the difference between two single binary digits?

a) Full Adder b) Half Subtractor c) Full Subtractor d) BCD Adder

Answer: b) Half Subtractor

6 A 4-bit adder-subtractor circuit can perform:

a) Only addition b) Only subtraction c) Both addition and subtraction d) Multiplication

Answer: c) Both addition and subtraction

7 What is the primary advantage of a carry look-ahead adder?

a) Reduces power consumption b) Increases propagation delay

c) Reduces propagation delay d) Simplifies circuit design

Answer: c) Reduces propagation delay

8 In K-map minimization, a group of 8 adjacent 1s eliminates how many variables?

a) 1 b) 2 c) 3 d) 4

Answer: c) 3

9 The Quine-McCluskey method is particularly useful for minimizing Boolean functions with:

a) Few variables b) Many variables c) Only two variables d) Only one output

Answer: b) Many variables

10 Which combinational circuit is used to add two BCD numbers?

a) Full Adder b) Ripple Carry Adder c) BCD Adder d) Excess-3 Adder

Answer: c) BCD Adder

11 How many inputs does a Half Subtractor have?

a) 1 b) 2 c) 3 d) 4

Answer: b) 2

12 What is the output of a Half Subtractor?

a) Sum and Carry b) Difference and Borrow

c) Sum and Difference d) Carry and Borrow

Answer: b) Difference and Borrow

13 Which circuit is a modified BCD adder that works with Excess-3 code inputs?

a) Ripple Carry Adder b) Carry Look-Ahead Adder

c) Excess-3 Adder d) Parallel Adder

Answer: c) Excess-3 Adder

14To realize a three-level logic circuit, which forms can be used?

a) Only SOP b) Only POS c) NAND-NAND or NOR-NOR d) Universal gates only

Answer: c) NAND-NAND or NOR-NOR

15 The main goal of minimization techniques in digital logic is to:

a) Increase circuit complexity b) Reduce the number of gates

c) Increase propagation delay d) Use more components

Answer: b) Reduce the number of gates

16 Which method is suitable for minimizing switching functions with up to 6 variables?

a) Quine-McCluskey method b) K-Map

c) Boolean theorems only d) Tabular method only

Answer: b) K-Map

17 What is the sum output of a Half Adder with inputs A and B?

a) 𝐴⋅𝐵 b) 𝐴+𝐵 c) 𝐴⊕𝐵 d) 𝐴′+𝐵′

Answer: c) 𝐴⊕𝐵

18 The carry output of a Half Adder with inputs A and B is:

a) 𝐴⋅𝐵 b) 𝐴+𝐵 c) 𝐴⊕𝐵 d) 𝐴′+𝐵′

Answer: a) 𝐴⋅𝐵

19 The design of a 4-bit adder-subtractor circuit relies on using:

a) Half Adders b) Full Subtractors c) Full Adders d) Universal gates

Answer: c) Full Adders

20 What is the primary characteristic of a combinational logic circuit?

a) Output depends on present and past inputs b) Contains memory elements

c) Output depends only on present inputs d) Used for sequential operations

Answer: c) Output depends only on present inputs