ECE - DE - MCQ
UNIT 1
🔢 Number System and Codes
-
What is the decimal equivalent of binary number 1101?
A) 11
B) 13
C) 14
D) 15
✅ Answer: B) 13 -
Convert (45)₁₀ to binary:
A) 101101
B) 110101
C) 101011
D) 110011
✅ Answer: A) 101101 -
What is the hexadecimal representation of (255)₁₀?
A) FE
B) FF
C) F0
D) F1
✅ Answer: B) FF -
(111101)₂ is equivalent to which octal number?
A) 75
B) 77
C) 65
D) 61
✅ Answer: A) 75 -
What is 1's complement of binary number 100101?
A) 011010
B) 100010
C) 011011
D) 101010
✅ Answer: A) 011010 -
2's complement of 1100 is:
A) 0011
B) 0100
C) 1111
D) 0101
✅ Answer: D) 0101 -
Perform binary addition: 1011 + 1101 = ?
A) 11000
B) 10100
C) 10000
D) 11110
✅ Answer: A) 11000 -
Binary subtraction: 10010 - 01001 = ?
A) 01001
B) 10001
C) 01101
D) 11111
✅ Answer: A) 01001 -
What is the BCD code for decimal number 39?
A) 0011 1001
B) 0100 0011
C) 0011 0110
D) 0111 0011
✅ Answer: A) 0011 1001 -
Which ASCII code represents the character 'A'?
A) 65
B) 66
C) 67
D) 64
✅ Answer: A) 65 -
What is the Gray code for binary number 1010?
A) 1111
B) 1110
C) 1100
D) 1001
✅ Answer: B) 1110
🔣 Boolean Algebra and K-Map
-
According to Boolean algebra, A + A = ?
A) 1
B) A
C) 0
D) A'
✅ Answer: B) A -
Which is DeMorgan’s First Theorem?
A) (A + B)' = A'B'
B) (AB)' = A' + B'
C) (A + B)' = A + B
D) A' + B' = (AB)'
✅ Answer: A) (A + B)' = A'B' -
The expression AB + A'C is in which form?
A) POS
B) SOP
C) Canonical SOP
D) Canonical POS
✅ Answer: B) SOP -
Which Boolean expression represents the POS form?
A) AB + AC
B) (A + B)(A + C)
C) A + B + C
D) ABC + A'B'C'
✅ Answer: B) (A + B)(A + C) -
What is the simplified form of A + AB using Boolean algebra?
A) A
B) AB
C) B
D) A + B
✅ Answer: A) A -
What is the value of A ⊕ B (A XOR B) when A = 1 and B = 1?
A) 1
B) 0
C) A
D) B
✅ Answer: B) 0 -
In 4-variable K-map, how many cells are there?
A) 4
B) 8
C) 16
D) 32
✅ Answer: C) 16 -
In K-map, adjacent cells differ by:
A) 2 bits
B) 1 bit
C) 3 bits
D) No bits
✅ Answer: B) 1 bit -
Simplify using K-map: F(A, B, C) = Σ(1, 2, 3, 7)
A) A'C + AC
B) B + C
C) A + B
D) AB + BC
✅ Answer: A) A'C + AC
UNIT 2
🔘 Logic Gates – Symbols, Expressions, Truth Tables
1. Which logic gate has the output expression Y = A · B?
A) OR
B) AND
C) XOR
D) NOT
✅ Answer: B) AND
2. What is the output of an OR gate when both inputs are 0?
A) 1
B) 0
C) A
D) B
✅ Answer: B) 0
3. The NOT gate is also known as a:
A) Inverter
B) Repeater
C) Comparator
D) Amplifier
✅ Answer: A) Inverter
4. Which gate has the truth table where output is 1 only when inputs differ?
A) XOR
B) XNOR
C) NOR
D) AND
✅ Answer: A) XOR
5. What is the Boolean expression for a NAND gate?
A) A + B
B) A · B
C) (A · B)'
D) (A + B)'
✅ Answer: C) (A · B)'
6. The symbol with a curved back and one input is for which gate?
A) NOT
B) AND
C) OR
D) XOR
✅ Answer: A) NOT
7. Which logic gate gives a HIGH output only when both inputs are LOW?
A) NOR
B) NAND
C) AND
D) OR
✅ Answer: A) NOR
8. The truth table of XNOR gate gives output 1 when:
A) Inputs are different
B) Both inputs are 1
C) Both inputs are 0
D) Inputs are the same
✅ Answer: D) Inputs are the same
9. Which gate has the output expression Y = (A + B)'?
A) NAND
B) NOR
C) AND
D) OR
✅ Answer: B) NOR
10. Which of the following are Universal Gates?
A) AND and OR
B) XOR and XNOR
C) NAND and NOR
D) NOT and AND
✅ Answer: C) NAND and NOR
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🧮 Logic Circuit Realization – Using Universal Gates
11. Which gate can be used to construct all other gates?
A) AND
B) OR
C) NAND
D) XOR
✅ Answer: C) NAND
12. How many NAND gates are required to construct a NOT gate?
A) 1
B) 2
C) 3
D) 4
✅ Answer: A) 1
13. Using NOR gates, how do you create an OR gate?
A) 2 NOR gates
B) 3 NOR gates
C) 4 NOR gates
D) Not possible
✅ Answer: B) 3 NOR gates
14. Which combination gives AND gate using NAND gates?
A) Invert inputs, then NAND
B) NAND output, then invert
C) NAND output twice
D) NOR of inputs
✅ Answer: B) NAND output, then invert
15. To create an AND gate using only NOR gates, you need:
A) 2 gates
B) 3 gates
C) 4 gates
D) 1 gate
✅ Answer: C) 4 gates
16. Which gate’s output is 0 only when both inputs are 1?
A) OR
B) XOR
C) NAND
D) AND
✅ Answer: C) NAND
17. What is the implementation of A + B using NAND gates?
A) Invert A and B, then NAND
B) A NAND B
C) NAND followed by NOR
D) Cannot be done
✅ Answer: A) Invert A and B, then NAND
18. Which logic gate is used in parity checkers?
A) AND
B) OR
C) XOR
D) NOR
✅ Answer: C) XOR
19. XNOR gate is also called:
A) Even parity gate
B) Difference gate
C) NOT gate
D) Zero detector
✅ Answer: A) Even parity gate
20. The output of a NOR gate is 1 when:
A) Any one input is 1
B) B
oth inputs are 1
C) Both inputs are 0
D) One input is 0
✅ Answer: C) Both inputs are 0
UNIT 3
🔢 Arithmetic Circuits: Adders and Subtractors
1. What are the inputs to a half adder?
A) A, B, Carry-in
B) A, B
C) A, Carry-in
D) A, B, Carry-out
✅ Answer: B) A, B
2. The sum output of a half adder is:
A) A AND B
B) A OR B
C) A XOR B
D) A XNOR B
✅ Answer: C) A XOR B
3. Which of the following is used in a full adder but not in a half adder?
A) AND gate
B) XOR gate
C) Carry-in
D) OR gate
✅ Answer: C) Carry-in
4. How many inputs and outputs does a full adder have?
A) 2 inputs, 1 output
B) 3 inputs, 2 outputs
C) 2 inputs, 2 outputs
D) 3 inputs, 1 output
✅ Answer: B) 3 inputs, 2 outputs
5. The carry output of a full adder is:
A) A XOR B
B) A AND B
C) AB + BC + AC
D) A OR B
✅ Answer: C) AB + BC + AC
6. The difference output of a half subtractor is:
A) A XOR B
B) A AND B
C) A OR B
D) A NAND B
✅ Answer: A) A XOR B
7. Which component is required to design a full subtractor?
A) 1 half subtractor and 1 OR gate
B) 2 half subtractors and 1 OR gate
C) 2 half adders and 1 AND gate
D) 2 full adders
✅ Answer: B) 2 half subtractors and 1 OR gate
8. The borrow output in a half subtractor is:
A) A AND B
B) A' AND B
C) A XOR B
D) A OR B
✅ Answer: B) A' AND B
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💾 Data Processing Circuits: Encoder, Decoder, MUX, DEMUX
9. How many output lines does a 4-to-2 encoder have?
A) 2
B) 4
C) 3
D) 1
✅ Answer: A) 2
10. The number of output lines in an 8-to-3 encoder is:
A) 2
B) 3
C) 4
D) 8
✅ Answer: B) 3
11. What is the function of an encoder?
A) Decodes input data
B) Generates sum and carry
C) Converts input to binary code
D) Multiplies input signals
✅ Answer: C) Converts input to binary code
12. Which logic circuit converts binary data from n input lines to a maximum of 2ⁿ output lines?
A) Encoder
B) Decoder
C) Multiplexer
D) Comparator
✅ Answer: B) Decoder
13. How many output lines does a 3-to-8 decoder have?
A) 3
B) 8
C) 6
D) 4
✅ Answer: B) 8
14. A 2-to-4 decoder has how many input and output lines?
A) 2 inputs, 4 outputs
B) 4 inputs, 2 outputs
C) 2 inputs, 2 outputs
D) 4 inputs, 4 outputs
✅ Answer: A) 2 inputs, 4 outputs
15. Which circuit has multiple input lines and selects one line to pass to the output?
A) Decoder
B) Encoder
C) Multiplexer
D) Demultiplexer
✅ Answer: C) Multiplexer
16. How many select lines are needed for a 4-to-1 multiplexer?
A) 1
B) 2
C) 3
D) 4
✅ Answer: B) 2
17. What is the function of a demultiplexer?
A) Combines data lines
B) Selects input lines
C) Routes one input to multiple outputs
D) Generates binary numbers
✅ Answer: C) Routes one input to multiple outputs
18. A 1-to-4 demultiplexer requires how many select lines?
A) 1
B) 2
C) 3
D) 4
✅ Answer: B) 2
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✅ Parity Generator and Checker
19. A 3-bit even parity generator produces output 1 when:
A) Number of 1s is even
B) Number of 1s is odd
C) All bits are 0
D) All bits are 1
✅ Answer: B) Number of 1s is odd
20. The parity checker is
used to:
A) Detect errors
B) Count 1s
C) Convert binary to decimal
D) Add bits
✅ Answer: A) Detect errors
UNIT 4
🔄 Flip-Flops and Latches
1. Which gate is used in basic SR Latch construction?
A) XOR
B) NAND
C) XNOR
D) AND
✅ Answer: B) NAND
2. A latch is a:
A) Combinational circuit
B) Sequential circuit without clock
C) Clocked sequential circuit
D) Multiplexer
✅ Answer: B) Sequential circuit without clock
3. What is the output of an SR latch when S = 0 and R = 0 (NAND-based)?
A) Invalid
B) No change
C) Reset
D) Set
✅ Answer: B) No change
4. In NOR-based SR latch, which input combination leads to invalid state?
A) S=1, R=1
B) S=0, R=0
C) S=1, R=0
D) S=0, R=1
✅ Answer: A) S=1, R=1
5. Which flip-flop stores one bit of data and has a clock input?
A) SR
B) D
C) T
D) All of these
✅ Answer: D) All of these
6. What is the purpose of the ‘Clock’ in a flip-flop?
A) Provide delay
B) Synchronize operations
C) Invert output
D) Store data
✅ Answer: B) Synchronize operations
7. Which of the following is not a type of triggering?
A) Level triggering
B) Pulse triggering
C) Edge triggering
D) Voltage triggering
✅ Answer: D) Voltage triggering
8. The output of a D flip-flop is:
A) Same as input
B) Always 0
C) Always 1
D) Inverted input
✅ Answer: A) Same as input
9. The JK flip-flop avoids the invalid state of which other flip-flop?
A) D
B) SR
C) T
D) Master-slave
✅ Answer: B) SR
10. When both J and K are high in a JK flip-flop, the output will:
A) Toggle
B) Set
C) Reset
D) No change
✅ Answer: A) Toggle
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⏱️ More on Flip-Flops and Applications
11. T flip-flop is derived from which flip-flop?
A) JK
B) SR
C) D
D) Master-slave
✅ Answer: A) JK
12. Which flip-flop is commonly used in counters?
A) D flip-flop
B) T flip-flop
C) SR flip-flop
D) Clocked SR
✅ Answer: B) T flip-flop
13. Which flip-flop uses two clocked JK flip-flops to eliminate race condition?
A) D flip-flop
B) T flip-flop
C) Master-Slave JK
D) SR flip-flop
✅ Answer: C) Master-Slave JK
14. What is the purpose of PRESET and CLEAR in flip-flops?
A) Delay outputs
B) Eliminate race condition
C) Initialize or reset outputs
D) Increase speed
✅ Answer: C) Initialize or reset outputs
15. Flip-flops are mainly used in:
A) Memory devices
B) Adders
C) Encoders
D) Decoders
✅ Answer: A) Memory devices
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🔢 Counters
16. What is a counter?
A) Logic adder
B) Memory cell
C) Sequential circuit that counts pulses
D) Encoder
✅ Answer: C) Sequential circuit that counts pulses
17. Asynchronous counter is also known as:
A) Parallel counter
B) Serial counter
C) Ripple counter
D) Decade counter
✅ Answer: C) Ripple counter
18. What is the major drawback of asynchronous counters?
A) High power
B) Limited speed
C) Propagation delay
D) High cost
✅ Answer: C) Propagation delay
19. Which counter has all flip-flops triggered by the same clock?
A) Ripple counter
B) Serial counter
C) Synchronous counter
D) Decade counter
✅ Answer: C) Synchronous counter
20. A decade counter counts from:
A) 0 to 9
B) 0 to 10
C) 0 to 15
D) 1 to 10
✅ Answer: A) 0 to 9
UNIT 5
🔁 Shift Registers
1. What is the primary function of a shift register?
A) Perform arithmetic operations
B) Store and transfer data
C) Decode binary values
D) Generate clock pulses
✅ Answer: B) Store and transfer data
2. In a Serial In Serial Out (SISO) shift register, data is:
A) Entered and removed in parallel
B) Entered in serial, read in parallel
C) Entered and read in serial
D) Stored permanently
✅ Answer: C) Entered and read in serial
3. Which shift register allows loading all bits at the same time and outputs them one by one?
A) Serial In Serial Out
B) Serial In Parallel Out
C) Parallel In Serial Out
D) Parallel In Parallel Out
✅ Answer: C) Parallel In Serial Out
4. Which shift register outputs all bits simultaneously after shifting in serial data?
A) SISO
B) PISO
C) SIPO
D) PIPO
✅ Answer: C) SIPO
5. Which shift register has both parallel input and parallel output?
A) SIPO
B) PIPO
C) SISO
D) PISO
✅ Answer: B) PIPO
6. A 4-bit shift register can hold:
A) 2 bits
B) 4 bits
C) 8 bits
D) 1 byte
✅ Answer: B) 4 bits
7. Which of the following is not an application of shift registers?
A) Serial-to-parallel conversion
B) Parallel-to-serial conversion
C) Data storage
D) Multiplication
✅ Answer: D) Multiplication
8. Shift registers operate based on:
A) Combinational logic
B) Counters
C) Clock pulses
D) Cache memory
✅ Answer: C) Clock pulses
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💾 Memory – ROM and Types
9. ROM stands for:
A) Read On Memory
B) Random Only Memory
C) Read Only Memory
D) Rapid Output Memory
✅ Answer: C) Read Only Memory
10. Which type of ROM can be programmed once by the user?
A) PROM
B) EPROM
C) EEPROM
D) Flash
✅ Answer: A) PROM
11. Which ROM type can be erased using UV light?
A) PROM
B) EPROM
C) EEPROM
D) Flash
✅ Answer: B) EPROM
12. EEPROM can be erased using:
A) Ultraviolet light
B) Heat
C) Electrical signals
D) Magnetic field
✅ Answer: C) Electrical signals
13. Which ROM type is commonly used in USB drives and memory cards?
A) EEPROM
B) Flash
C) EPROM
D) PROM
✅ Answer: B) Flash
14. ROM is generally used for:
A) Temporary storage
B) Storing boot programs
C) Arithmetic operations
D) Cache memory
✅ Answer: B) Storing boot programs
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🧠 Memory – RAM, Cache, and Comparison
15. What does RAM stand for?
A) Read and Memory
B) Random Access Memory
C) Rapid Access Module
D) Registered Arithmetic Memory
✅ Answer: B) Random Access Memory
16. Which type of RAM uses flip-flops to store data?
A) DRAM
B) Flash
C) SRAM
D) EEPROM
✅ Answer: C) SRAM
17. DRAM stores data using:
A) Flip-flops
B) Capacitors
C) Latches
D) Registers
✅ Answer: B) Capacitors
18. Which of the following is faster but more expensive?
A) DRAM
B) SRAM
C) ROM
D) PROM
✅ Answer: B) SRAM
19. Which of the following best compares RAM and ROM?
A) RAM is permanent, ROM is volatile
B) RAM is faster, ROM is slower
C) RAM stores firmware, ROM stores data
D) ROM loses data when power is off
✅ Answer: B) RAM is faster, ROM is slower
20. Cache memory is used to:
A) Store BIOS
B) Backup hard disk
C) Provide faster access to frequently used data
D) Stor
e output permanently
✅ Answer: C) Provide faster access to frequently used data
