Digital Logic MCQ Quiz - Objective Question with Answer for Digital Logic - Download Free PDF
Last updated on May 6, 2025
Latest Digital Logic MCQ Objective Questions
Digital Logic Question 1:
Exclusive OR(XOR) is a special gate whose output is 1 only if:
Answer (Detailed Solution Below)
Digital Logic Question 1 Detailed Solution
Formula:
A XOR B ≡ A ⊕ B ≡ A̅.B + A.B̅
XOR: Truth Table
A̅ |
B̅ |
A ⊕ B |
0 |
0 |
0 |
0 |
1 |
1 |
1 |
0 |
1 |
1 |
1 |
0 |
Option 1: Incorrect
Fails for input (A = 0, B = 0)
Since Output is 0
Option 2: Incorrect
Fails for input (A = 1, B = 1)
Since Output is 0
Option 3: correct
Valid all the cases of truth table
Option 4: Incorrect
Fails for input (A = 1, B = 1)
Since Output is 0
Digital Logic Question 2:
A combinational logic circuit that is used when it is desired to send data from two or more source through a single transmission line is known as _________.
Answer (Detailed Solution Below)
Digital Logic Question 2 Detailed Solution
Encoder:
An encoder has 2n input lines and n output lines. In the encoder, the output lines generate the binary code corresponding to the input value which is active high.
Decoder:
It is a multi-input and multi-output logic circuit that converts coded inputs into coded outputs where input and output codes are different. Input code has fewer bits than output code. There is one to one mapping from input to output.
Multiplexer:
It is a digital switch. It allows digital information from several sources to be routed onto a single output line. A basic multiplexer has several data input lines and a single output line. The selection of a particular input line is controlled by selection lines. It is many to one mapping and provides the digital equivalent of an analog selector switch. Therefore it is the correct answer
Demultiplexer:
It is a circuit that receives information on a single line and transmits information on one of the 2n output lines. Selection of output line is controlled by values of n selection lines.
Digital Logic Question 3:
Consider the following min term expression for F.
F (P, Q, R, S) = ∑ 0, 2, 5, 7, 8, 10, 13, 15
The min-terms 2, 7, 8 and 13 are ‘do not care’ terms. The minimal sum-of-products form for F is
Answer (Detailed Solution Below)
Digital Logic Question 3 Detailed Solution
F (P, Q, R, S) = ∑ 0, 2, 5, 7, 8, 10, 13, 15
Don’t care min terms are 2, 7, 8, 13
By plotting the K-map, the minimal SOP (sum of products) can be found.
Explanation –
While putting the terms to k-map following things happen,
- 3rd and 4th columns are swapped
- 3rd and 4th rows.
- term 2 is going to (0, 3) column instead of (0, 2)
- 8 is going to (3, 0) instead of (2,0)
Solving, the above K-map, we get Q̅S̅ + QS
Digital Logic Question 4:
What is the octal equivalent of (F3B1)16?
Answer (Detailed Solution Below)
Digital Logic Question 4 Detailed Solution
The correct answer is 171661
Key Points
- To find the octal equivalent of a hexadecimal number, you can convert each hexadecimal digit to its binary equivalent and then group the binary digits into groups of three (since each octal digit represents three binary digits).
- Let's convert each hexadecimal digit of (F3B1)16 to binary:
- F = 1111
- 3 = 0011
- B = 1011
- 1 = 0001
- Now group the binary digits into sets of three:
- 1111 0011 1011 0001
- Now convert each set of three binary digits to octal:
- 001 111 001 110 110 001
- Combine these octal digits: 171661.
Therefore, the octal equivalent of (F3B1)16 is option 3) 171661.
Digital Logic Question 5:
Which of the followings are sequential circuit?
A. Flip flop
B. Multiplexer
C. Counter
D. Decoder
E. Adder
Choose the correct answer from the options given below :
Answer (Detailed Solution Below)
Digital Logic Question 5 Detailed Solution
The correct answer is 2) A, C Only.
Key Points
- Sequential circuits are types of circuits where the output depends not just on the current inputs, but also on the history of inputs. This means they have memory elements that store previous states.
- Flip flop is a basic memory element used in sequential circuits, which can store one bit of data.
- Counter is a sequential circuit that goes through a prescribed sequence of states upon the application of input pulses.
Additional Information
- Multiplexer (MUX) is a combinational circuit that selects one of many input signals and forwards the selected input into a single line. It does not store any state information, hence it is not a sequential circuit.
- Decoder is also a combinational circuit that converts binary information from n input lines to a maximum of 2^n unique output lines. It does not have memory, so it is not a sequential circuit.
- Adder is a combinational circuit used for adding binary numbers. It does not store any state information, hence it is not a sequential circuit.
Top Digital Logic MCQ Objective Questions
Binary number 101110110 is equal to decimal number _______.
Answer (Detailed Solution Below)
Digital Logic Question 6 Detailed Solution
Download Solution PDF- The correct answer is option 3, i.e., 374.
- Binary number 101110110 is equal to decimal number 374.
- Following method can be used to convert Binary number to Decimal number:
- (101110110)2 = (1 x 28) + (0 x 27) + (1 x 26) + (1 x 25) + (1 x 24) + (0 x 23) + (1 x 22) + (1 x 21) + (0 x 20)
- (101110110)2 = 256 + 0 + 64 + 32 + 16 + 0 + 4 + 2 + 0
- (101110110)2 = 374
One megabyte In base 2 (binary) Is equivalent to .
Answer (Detailed Solution Below)
Digital Logic Question 7 Detailed Solution
Download Solution PDFThe correct answer is 220 bytes.
Key Points
- 1 Megabyte is equal to 1000000 bytes (decimal).
- 1 MB = 106 B in base 10 (SI).
- 1 Megabyte is equal to 1048576 bytes (binary).
- 1 MB = 220 B in base 2.
- Byte is the basic unit of digital information transmission and storage, used extensively in information technology, digital technology, and other related fields. It is one of the smallest units of memory in computer technology, as well as one of the most basic data measurement units in programming.
- The earliest computers were made with the processor supporting 1 byte commands, because in 1 byte you can send 256 commands. 1 byte consists of 8 bits,
- Megabyte (MB) is a unit of transferred or stored digital information, which is extensively used in information and computer technology.
- In SI, one megabyte is equal to 1,000,000 bytes. At the same time, practically 1 megabyte is used as 220 B, which means 1,048,576 bytes.
Binary 110110101 is equal to decimal ________.
Answer (Detailed Solution Below)
Digital Logic Question 8 Detailed Solution
Download Solution PDFBinary 110110101 is equal to decimal 437
Calculation:
1 1 0 1 1 0 1 0 1
From rightmost first column as follows
=> (20 * 1) + (21 * 0) + (22 * 1) + (23 * 0) + (24 * 1) + (25 * 1) + (26 * 0) + (27 * 1) + (28 * 1)
=> (1) + (0) + (4) + (0) + (16) + (32) + (0) + (128) + (256)
Decimal value =>437
Convert the hexadecimal number C6 to binary number.
Answer (Detailed Solution Below)
Digital Logic Question 9 Detailed Solution
Download Solution PDFThe correct answer is 11000110
Key Points
- To convert the hexadecimal number C6 to a binary number, you can convert each hexadecimal digit to its 4-bit binary representation.
- C in hexadecimal is 12 in decimal, which is 1100 in binary.
- 6 in hexadecimal is 6 in decimal, which is 0110 in binary.
- So, the binary representation of C6 is 11000110.
Additional InformationHere are the decimal numbers 1 to 15 represented in both hexadecimal and binary forms:
- Decimal 1: Hexadecimal 1, Binary 0001
- Decimal 2: Hexadecimal 2, Binary 0010
- Decimal 3: Hexadecimal 3, Binary 0011
- Decimal 4: Hexadecimal 4, Binary 0100
- Decimal 5: Hexadecimal 5, Binary 0101
- Decimal 6: Hexadecimal 6, Binary 0110
- Decimal 7: Hexadecimal 7, Binary 0111
- Decimal 8: Hexadecimal 8, Binary 1000
- Decimal 9: Hexadecimal 9, Binary 1001
- Decimal 10: Hexadecimal A, Binary 1010
- Decimal 11: Hexadecimal B, Binary 1011
- Decimal 12: Hexadecimal C, Binary 1100
- Decimal 13: Hexadecimal D, Binary 1101
- Decimal 14: Hexadecimal E, Binary 1110
- Decimal 15: Hexadecimal F, Binary 1111
The sum of two binary numbers 1101111 and 1100101 is ______.
Answer (Detailed Solution Below)
Digital Logic Question 10 Detailed Solution
Download Solution PDFThe sum of two binary numbers 1101111 and 1100101 is (11010100)2
Note: In Binary addition, 1 + 1 = 10 (0 is sum value and 1 is carry), 1 + 0 = 1, 0 + 1 = 1 and 0 + 0 = 0.
Calculation:
1 1 1 1 1 (Carry values)
1 1 0 1 1 1 1 (Binary number 1)
0 1 0 0 0 (Sum values)
+1 1 0 0 1 0 1 (Binary number 2)
-------------------
1 1 0 1 0 1 0 0 (Answer)
-------------------
The Octal equivalent of the binary number 1011101011 is:
Answer (Detailed Solution Below)
Digital Logic Question 11 Detailed Solution
Download Solution PDFAnswer: Option 2
Explanation:
An octal Equivalent of a binary number is obtained by grouping 3 bits from right to left.
001 | 011 | 101 | 011 |
1 | 3 | 5 | 3 |
So Octal Equivalent: 1353
Important Points
Binary to Octal code
000 |
001 |
010 |
011 |
100 |
101 |
110 |
111 |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
The 8-bit 2's complement form of the number -14 is ______.
Answer (Detailed Solution Below)
Digital Logic Question 12 Detailed Solution
Download Solution PDFCalculation:
14 in binary form is represented as:
1410 = (00001110)2
Taking the 1's complement of the above, we get 11110001
Adding 1 to the 1's complement, we get the 2's complement representation of the number, i.e. 11110010
Since there is a 1 in the MSB, the number is a negative number with value -14.
∴ The 2's complement of -6410 contains 7 bits.
Boolean algebra obeys
Answer (Detailed Solution Below)
Digital Logic Question 13 Detailed Solution
Download Solution PDF
Name |
AND Form |
OR Form |
Identity law |
1.A = A |
0 + A = A |
Null Law |
0.A = 0 |
1 + A = 1 |
Idempotent Law |
A.A = A |
A + A = A |
Inverse Law |
AA’ = 0 |
A + A’ = 1 |
Commutative Law |
AB = BA |
A + B = B + A |
Associative Law |
(AB)C |
(A + B) + C = A + (B + C) |
Distributive Law |
A + BC = (A + B)(A + C) |
A(B + C) = AB + AC |
Absorption Law |
A(A + B) = A |
A + AB = A |
De Morgan’s Law |
(AB)’ = A’ + B’ |
(A + B)’ = A’B’ |
The number of 1s in the binary representation of (3 ⋆ 4096 + 15 ⋆ 256 + 5 ⋆ 16 + 3) are
Answer (Detailed Solution Below)
Digital Logic Question 14 Detailed Solution
Download Solution PDFApplication:
Decimal value = (3 ⋆ 4096 + 15 ⋆ 256 + 5 ⋆ 16 + 3)
It can be written as:
(2 + 1) × 212 + (8 + 4 + 2 + 20) × 28 + (4 + 1) × 24 + (2 + 1) × 20
21 × 212 + 20 × 212 + (23 + 22 + 21 + 20) × 28 + (22 + 20) × 24 + (21 + 20) × 20
This can be written as:
213 + 212 + 211 + 210 + 29 × 28 + 26 + 24 + 21 + 20
The binary representation will be:
(11111101010011)2
Which of the following pairs of octal and binary numbers are NOT equal?
Answer (Detailed Solution Below)
Digital Logic Question 15 Detailed Solution
Download Solution PDFThe correct answer is (11010)2 = (62)8
Key Points
Binary numbers and octal numbers are both used in computing. They are different ways of representing the same value - just like how "10" and "ten" are different ways of expressing the same quantity in decimal.
- Each digit of an octal number represents three binary digits because 23 = 8. Here's the mapping:
- "000" => "0"
- "001" => "1"
- "010" => "2"
- "011" => "3"
- "100" => "4"
- "101" => "5"
- "110" => "6"
- "111" => "7"
- Now let's convert the binary numbers to their equivalent octal numbers.
- (111 110 111)2 = (7 6 7)8
- (110 110 101)2 = (6 6 5)8
- (10 101 . 110)2 = (2 5 . 6)8
- (11 010)2 = (3 2)8 - Corrupted as the corresponding octal number should be (32)8 instead of (62)8.
Therefore, the 4th pair, (11010)2 = (62)8, is not equal.