FULL ADDER

1.
What does a full adder do?
A) Adds 2 bits
 B) Adds 3 bits
C) Adds 1 bit
D) Adds 4 bits
Answer: B

2.
Inputs to a full adder are:
A) A, B only
B) A, B, Carry-out
C) A, B, Carry-in
D) A, Carry-in only
Answer: C

3.
How many outputs does a full adder have?
A) 1
B) 2
C) 3
D) 4
Answer: B (Sum, Carry-out)

4.
Which gates are typically used to build a full adder?
A) OR, NOR
B) XOR, AND, OR
C) NAND only
D) NOT, AND
Answer: B
5.
How many full adders are needed to add two 4-bit binary numbers?
A) 1
B) 2
C) 3
D) 4
Answer: D

HALF ADDER
6.
What does a half adder do?
A) Adds 2 bits without carry
B) Adds 3 bits
C) Subtracts 2 bits
D) Adds 2 decimal numbers
Answer: A

7.
How many inputs does a half adder have?
A) 3
B) 2
C) 1
D) 4
Answer: B
8.
How many outputs does a half adder provide?
A) 1
B) 2
C) 3
D) 4
Answer: B (Sum and Carry)

9.
Which logic gates are used in a half adder?
A) XOR and AND
B) OR and NOT
C) NAND and NOR
D) Only OR
Answer: A

10.
Half adder cannot handle:
A) Decimal input
B) Carry input
C) Binary input
D) XOR operation
Answer: B

DECODER
11.
What is the function of a decoder?
A) To encode data
B) To multiplex data
C) To convert binary input to one active output
D) To perform addition
Answer: C

12.
A 3-to-8 decoder has how many inputs and outputs?
A) 3 inputs, 8 outputs
B) 8 inputs, 3 outputs
C) 4 inputs, 16 outputs
D) 2 inputs, 4 outputs
Answer: A

13.
Which of these is an application of a decoder?
A) Data encryption
B) Binary addition
C) Memory addressing
D) Full adder
Answer: C

14.
A 2-to-4 decoder activates:
A) All outputs simultaneously
B) One output at a time
C) Two outputs
 D) Four outputs always
Answer: B

15.
Which gate is commonly used in decoders?
A) AND
B) XOR
C) NOT
D) NAND
Answer: A

ENCODER
16.
What is the purpose of an encoder?
A) Convert binary to decimal
B) Convert analog to digital
C) Convert 1-of-n input into binary code
D) Perform addition
Answer: C

17.
How many outputs does a 4-to-2 encoder have?
A) 2
B) 4
 C) 1
D) 8
Answer: A

18.
Which input condition is valid for a simple encoder?
A) All inputs are 1
B) More than one input active
C) Only one input active at a time
D) No input active
Answer: C

19.
An encoder is the inverse of:
A) Multiplexer
B) Demultiplexer
C) Decoder
D) Adder
Answer: C

20.
A priority encoder resolves:
A) Input conflicts
B) Output priority
C) Multiplexing
D) Address resolution
Answer: A
 MULTIPLEXER
21.
A multiplexer (MUX) does what?
A) Routes one output to many inputs
B) Selects one input from many and sends it to output
C) Adds multiple numbers
D) Encodes binary data
Answer: B

22.
How many selection lines are needed for a 4-to-1 MUX?
A) 2
B) 4
C) 1
D) 3
Answer: A

23.
A multiplexer is also called:
A) Data generator
B) Data selector
C) Adder
D) Splitter
Answer: B

24.
A 2-to-1 MUX selects:
 A) One of 2 inputs
B) One of 4 inputs
C) Two outputs
D) No input
Answer: A

25.
Which gate is commonly used in multiplexers?
A) AND
B) OR
C) NOT
D) All of the above
Answer: D

FLIP-FLOP
26.
Flip-flop is used for:
A) Multiplication
B) Counting
C) Storage of 1-bit data
D) Addition
Answer: C

27.
 The basic flip-flop is:
A) JK
B) D
C) SR
D) T
Answer: C

28.
What is the output of a D flip-flop when D = 1 and clock triggers?
A) 0
B) 1
C) Unchanged
D) Toggles
Answer: B

29.
Which flip-flop toggles on every clock pulse?
A) SR
B) D
C) JK
D) T
Answer: D

30.
Which condition is invalid for SR flip-flop?
A) S = 0, R = 1
B) S = 1, R = 0
C) S = 0, R = 0
D) S = 1, R = 1
Answer: D
(…continued in next message due to length limit…)

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continued
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Continuing from question 30, here are questions 31 to 100 covering flip-flops and registers and reinforcing earlier topics.

FLIP-FLOP (continued)
31.
A JK flip-flop avoids the invalid state of:
A) SR flip-flop
B) D flip-flop
C) T flip-flop
D) None
Answer: A

32.
What is the output of a T flip-flop if T = 0?
A) Toggles
B) Resets
C) No change
D) Set
Answer: C

33.
Edge triggering in flip-flops means:
A) Change on high signal
B) Change on rising/falling clock edge
C) No change at all
D) Always active
Answer: B

34.
D flip-flop stores data from:
A) Output
B) Set pin
C) D input line
D) Clock
 Answer: C

35.
Flip-flops are used in:
A) Memory units
B) Adders
C) Decoders
D) Encoders
Answer: A

36.
Master-slave flip-flop is built using:
A) One D flip-flop
B) Two flip-flops in series
C) NAND gates
D) Registers
Answer: B

37.
Which flip-flop is best for counters?
A) D
B) T
C) SR
D) JK
Answer: B

38.
Clock signal in flip-flops is used for:
A) Turning off the circuit
 B) Triggering state change
C) Power saving
D) Error detection
Answer: B

39.
SR flip-flop is constructed using:
A) XOR gates
B) NAND or NOR gates
C) OR gates
D) Buffers
Answer: B

40.
Flip-flops store:
A) Bit streams
B) Logic gates
C) Binary data
D) Program code
Answer: C

REGISTERS
41.
What is a register?
 A) Output device
B) Data storage device
C) Logical gate
D) Clock circuit
Answer: B

42.
Registers are used to store:
A) Only instructions
B) One bit
C) One or more bits
D) Only carry bits
Answer: C

43.
Which device stores multiple flip-flops together?
A) Decoder
B) Register
C) Counter
D) Encoder
Answer: B

44.
A 4-bit register uses how many flip-flops?
A) 1
B) 2
C) 3
D) 4
Answer: D
45.
Which type of register shifts data left/right?
A) Circular register
B) ROM
C) Shift register
D) Counter
Answer: C

46.
What is a parallel-in, parallel-out register?
A) Serial port
B) I/O port
C) Register that loads and outputs data in parallel
D) Counter
Answer: C

47.
Which register type is used in serial data transmission?
A) Shift register
B) Adder
C) Decoder
D) ROM
Answer: A

48.
The basic building block of a register is:
A) AND gate
B) D flip-flop
C) NOR gate
 D) NAND gate
Answer: B

49.
Registers are present in:
A) ALU
B) Control Unit
C) CPU
D) Memory chip only
Answer: C

50.
Which register loads data bit-by-bit?
A) Parallel-in
B) Serial-in
C) Memory
D) Accumulator
Answer: B

REINFORCEMENT (Mix of All Topics)

51–100: Here’s a variety for review.

51.
 Full adder carry-out depends on:
A) A and B
B) B and Cin
C) A and Cin
D) All three inputs
Answer: D

52.
A decoder's number of outputs is:
A) 2ⁿ
B) n²
C) n ²
D) 2n
Answer: A

53.
How many outputs does a 2-to-4 decoder have?
A) 2
B) 4
C) 8
D) 16
Answer: B

54.
In encoder, output is:
A) Always analog
B) One-hot code
C) Binary code
D) Excess-3 code
Answer: C
55.
Multiplexers are used for:
A) Reading memory
B) Device selection
C) Bit shifting
D) Code conversion
Answer: B

56.
A 4x1 multiplexer has how many control lines?
A) 1
B) 2
C) 4
D) 3
Answer: B

57.
An 8-to-1 multiplexer can select:
A) 4 outputs
B) 8 outputs
C) 1 of 8 inputs
D) 8 control lines
Answer: C

58.
**D flip-flop is called: **
A) Toggle flip-flop
B) Delay flip-flop
C) Set-reset flip-flop
 D) None
Answer: B

59.
Main difference between register and flip-flop:
A) Speed
B) Function
C) Capacity
D) Bit storage count
Answer: D

60.
Which flip-flop stores data on the clock’s falling edge?
A) Level triggered
B) Edge triggered
C) Transparent latch
D) Memory cell
Answer: B

61–100: Mixed & Scenario-Based

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 61–100 in similar style?

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ChatGPT said:
Great! Here's the continuation from question 61 to 100, in the same multiple-choice choose-one style, covering all seven topics: full adder, half
adder, decoder, encoder, multiplexer, flip-flop, and register.

CONTINUED: Mixed & Applied Understanding

61. What is the output of a full adder when A=1, B=1, Cin=1?
A) Sum = 0, Cout = 1
B) Sum = 1, Cout = 1
C) Sum = 0, Cout = 0
D) Sum = 1, Cout = 0
Answer: A

62. A half adder is suitable for:

A) Multi-bit addition
B) Subtraction
C) Adding two bits without carry-in
D) Multiplying two numbers
Answer: C

63. A 3-to-8 decoder requires how many enable inputs typically?

A) 0
B) 1
C) 2
D) 3
Answer: B
64. Which component can be used to build a decoder?
A) NAND gates
B) OR gates only
C) AND + NOT gates
D) XOR gates only
Answer: C

65. An encoder's output is undefined if:

A) No input is active
B) All inputs are active
C) Both A and B
D) Only one input is active
Answer: C

66. Which of these is not an application of encoders?

A) Keyboard encoding
B) Binary to decimal conversion
C) Interrupt prioritizing
D) Barcode reader
Answer: B

67. How many selection lines are required for a 16-to-1 multiplexer?
A) 2
B) 3
C) 4
D) 5
Answer: C
68. In a 4-to-1 MUX, how many input data lines are there?
A) 2
B) 4
C) 8
D) 16
Answer: B

69. Multiplexers can be used for:

A) Signal routing
B) Addition
C) Decoding
D) Storage
Answer: A

70. The primary use of a D flip-flop is:

A) Toggle logic
B) Shift data
C) Store a single bit
D) Add numbers
Answer: C

Flip-Flop & Register Logic

71. How many flip-flops are required to make an 8-bit register?

A) 2
B) 4
C) 8
D) 16
Answer: C

72. T flip-flop toggles when T=1 and:

A) Clock is high
B) Clock is low
C) Clock edge occurs
D) Clock is disabled
Answer: C

73. The output of a JK flip-flop is invalid when:

A) J = 0, K = 0
B) J = 1, K = 0
C) J = 0, K = 1
D) Never invalid
Answer: D

74. Which flip-flop is useful for frequency division?

A) SR
B) D
C) T
D) JK
Answer: C

75. What does a 'rising edge trigger' mean?

A) Trigger on low to high transition
B) Trigger on high to low
C) Trigger on level high
D) Trigger on level low
Answer: A

76. In a register, parallel loading refers to:

A) Loading 1 bit at a time
B) Loading all bits simultaneously
C) Loading using one clock cycle
D) Loading from memory
Answer: B

77. Which flip-flop has the least inputs?

A) SR
B) JK
C) D
D) T
Answer: C

78. A universal flip-flop is:

A) SR
B) D
C) JK
D) T
Answer: C

79. Registers are used in CPUs for:

A) Arithmetic only
B) Instruction decoding
C) Temporary data storage
D) Clock control
 Answer: C

80. A shift register moves data based on:

A) Power cycle
B) Clock pulse
C) External sensor
D) Multiplexer control
Answer: B

Application-Oriented & Conceptual

81. A decoder converts:

A) Binary input to single active output
B) Analog to digital
C) Serial to parallel
D) Carry to sum
Answer: A

82. A register with 8 flip-flops stores:

A) 1 byte
B) 2 bits
C) 8 bytes
D) 4 nibbles
Answer: A
83. The carry-out of a full adder is 1 when:
A) All inputs are 0
B) Only one input is 1
C) Two or more inputs are 1
D) Sum is 0
Answer: C

84. The main difference between multiplexer and decoder is:

A) Direction of data flow
B) Use of clock
C) Power consumption
D) Use of flip-flops
Answer: A

85. To represent 16 combinations, encoder must have:

A) 4 outputs
B) 3 outputs
C) 5 outputs
D) 2 outputs
Answer: A

86. What is a key feature of synchronous flip-flops?

A) Triggered by input level
B) Triggered by clock edge
C) Work without power
D) Toggle without input
Answer: B

87. Which logic circuit is used in a serial-to-parallel converter?

A) Register
B) Multiplexer
C) Decoder
D) Encoder
Answer: A

88. The 'reset' input in a flip-flop:

A) Sets output to 1
B) Holds current state
C) Clears output to 0
D) Increments counter
Answer: C

89. What is the output of a 4-to-2 priority encoder when input 3 is high?
A) 00
B) 01
C) 10
D) 11
Answer: D

90. In 8086 microprocessor, registers are used to:

A) Perform I/O operations
B) Decode instructions
C) Temporarily store data during processing
D) Set program counter
Answer: C
 Final 10: Concept Reinforcement

91. Which device outputs data depending on control signals?

A) Flip-flop
B) Decoder
C) Multiplexer
D) Register
Answer: C

92. The 'overflow' in adder circuits happens when:

A) Data exceeds memory
B) Result exceeds bit width
C) Inputs are zero
D) Clock fails
Answer: B

93. T flip-flop output toggles if:

A) T = 0
B) T = 1
C) Clock is low
D) No input is given
Answer: B

94. Which flip-flop is used in RAM circuits?

A) SR
B) JK
C) D
D) T
Answer: C
95. Parallel data transfer uses which register?
A) Serial-in
B) Serial-out
C) Parallel-in parallel-out
D) Shift register
Answer: C

96. Which unit uses multiplexers heavily?

A) Decoder
B) CPU ALU
C) Cache memory
D) Stack
Answer: B

97. The ‘Sum’ output in full adder is generated using:

A) XOR
B) OR
C) AND
D) NOT
Answer: A

98. Carry in full adder is derived using:

A) XOR gates
B) Multiple AND-OR operations
C) NOT and OR
D) NAND only
Answer: B
99. The flip-flop used to prevent race-around in JK is:
A) D flip-flop
B) Master-Slave JK
C) T flip-flop
D) Edge-triggered SR
Answer: B

100. Registers operate under control of:

A) Multiplexers
B) Clock signal
C) Memory
D) Decoder
Answer: B