## 50+ Top Combinational Circuits Multiple Choice Questions with Answers

### Combinational circuits are digital circuits that:

a) Have memory elements

b) Include flip-flops

c) Generate output based on input only

d) Use feedback

Answer: c) Generate output based on input only

### Which of the following is NOT a characteristic of combinational circuits?

a) Feedback loop

b) No memory

c) Output depends only on input

d) No internal state

Answer: a) Feedback loop

### The main building blocks of combinational circuits are:

a) Flip-flops

b) Counters

c) Logic gates

d) Memory units

Answer: c) Logic gates

### In a combinational circuit, the output is a function of:

a) Input and time

b) Output and time

c) Input and output

d) Input, output, and time

Answer: c) Input and output

### Which logic gate is used to perform the Boolean OR operation?

a) AND gate

b) NOT gate

c) NOR gate

d) OR gate

Answer: d) OR gate

### The output of a combinational circuit changes:

a) Continuously with time

b) At regular intervals

c) In response to clock signals

d) Instantaneously with input changes

Answer: d) Instantaneously with input changes

### A half-adder circuit adds:

a) Two binary numbers and a carry-in

b) Two binary numbers without a carry-in

c) Two decimal numbers and a carry-in

d) Two decimal numbers without a carry-in

Answer: b) Two binary numbers without a carry-in

### A full-adder circuit adds:

a) Two binary numbers and a carry-in

b) Two binary numbers without a carry-in

c) Three binary numbers and a carry-in

d) Three binary numbers without a carry-in

Answer: c) Three binary numbers and a carry-in

### A multiplexer is used to:

a) Add binary numbers

b) Multiply binary numbers

c) Divide binary numbers

d) Select one of many input lines based on a selected signal

Answer: d) Select one of many input lines based on a selected signal

### A demultiplexer is used to:

a) Add binary numbers

b) Multiply binary numbers

c) Divide binary numbers

d) Distribute data from one input line to multiple output lines based on a select signal

Answer: d) Distribute data from one input line to multiple output lines based on a select signal

### A decoder is used to:

a) Perform arithmetic operations

b) Convert binary codes into a more complex format

c) Convert binary codes into decimal numbers

d) Convert binary codes into their respective outputs

Answer: d) Convert binary codes into their respective outputs

### The number of input combinations for an n-input multiplexer is:

a) n

b) 2^n

c) n^2

d) 2n

Answer: b) 2^n

### Which gate is used to implement a binary decoder?

a) AND gate

b) OR gate

c) XOR gate

d) NOT gate

Answer: a) AND gate

### The output of a decoder is typically in:

a) Binary format

b) Gray code format

c) Decimal format

d) Octal format

Answer: a) Binary format

### A 3-to-8 decoder has how many input lines?

a) 3

b) 4

c) 8

d) 10

Answer: a) 3

### A priority encoder is used to:

a) Assign priority to different inputs

b) Combine multiple inputs into one output

c) Convert binary to BCD

d) Add binary numbers

Answer: a) Assign priority to different inputs

### In a priority encoder, the input with the highest priority is represented by:

a) The highest binary value

b) The lowest binary value

c) The middle binary value

d) Any arbitrary binary value

Answer: a) The highest binary value

### How many output lines does a 4-to-2 priority encoder have?

a) 2

b) 3

c) 4

d) 5

Answer: a) 2

### An encoder is used to:

a) Assign priority to different inputs

b) Combine multiple inputs into one output

c) Convert binary to BCD

d) Convert multiple input lines into a coded output

Answer: d) Convert multiple input lines into a coded output

### The output of an encoder is typically in:

a) Binary format

b) Gray code format

c) Decimal format

d) Octal format

Answer: a) Binary format

### How many output lines does an 8-to-3 encoder have?

a) 2

b) 3

c) 8

d) 10

Answer: b) 3

### A binary comparator is used to:

a) Perform arithmetic operations

b) Compare two binary numbers and produce outputs based on the comparison

c) Convert binary to BCD

d) Divide binary numbers

Answer: b) Compare two binary numbers and produce outputs based on the comparison

### The output of a binary comparator is typically in:

a) Binary format

b) Gray code format

c) Decimal format

d) Octal format

Answer: a) Binary format

### In a 4-bit binary comparator, how many outputs are used for the comparison result?

a) 2

b) 3

c) 4

d) 5

Answer: c) 4

### A BCD-to-7 segment decoder is used to:

a) Assign priority to different inputs

b) Combine multiple inputs into one output

c) Convert binary to BCD

d) Convert BCD to a format suitable for a 7-segment display

Answer: d) Convert BCD to a format suitable for a 7-segment display

### How many inputs does a BCD-to-7 segment decoder have?

a) 2

b) 3

c) 4

d) 5

Answer: c) 4

### In a BCD-to-7 segment decoder, each input combination corresponds to:

a) One segment of the display

b) One digit of the display

c) One position of the display

d) One character of the display

Answer: a) One segment of the display

### Which gate is used to implement a BCD-to-7 segment decoder?

a) AND gate

b) OR gate

c) XOR gate

d) NOT gate

Answer: a) AND gate

### How many outputs does a BCD-to-7 segment decoder have?

a) 2

b) 3

c) 4

d) 7

Answer: d) 7

### A magnitude comparator is used to compare:

a) Binary numbers and determine their relative magnitudes

b) The speed of different combinational circuits

c) The power consumption of different combinational circuits

d) The fan-out of different combinational circuits

Answer: a) Binary numbers and determine their relative magnitudes

### How many outputs does a 4-bit magnitude comparator have?

a) 1

b) 2

c) 3

d) 4

Answer: c) 3

### In a 4-bit magnitude comparator, the outputs are used to indicate whether:

a) The two numbers are equal

b) The first number is greater than the second number

c) The first number is less than the second number

d) All of the above

Answer: d) All of the above

### Which logic gate is used to implement a magnitude comparator?

a) AND gate

b) OR gate

c) XOR gate

d) NAND gate

Answer: c) XOR gate

### A binary subtractor is used to:

a) Add two binary numbers

b) Multiply two binary numbers

c) Divide two binary numbers

d) Subtract one binary number from another

Answer: d) Subtract one binary number from another

### In a 4-bit binary subtractor, how many output lines are used to represent the difference?

a) 2

b) 3

c) 4

d) 5

Answer: c) 4

### How many inputs does a 4-bit binary subtractor have?

a) 2

b) 3

c) 4

d) 5

Answer: c) 4

### Which logic gate is used to implement a binary subtractor?

a) AND gate

b) OR gate

c) XOR gate

d) NAND gate

Answer: c) XOR gate

### A comparator is used to:

a) Compare two analog signals

b) Compare two digital signals

c) Add two binary numbers

d) Multiply two binary numbers

Answer: b) Compare two digital signals

### A multiplexer with n select lines can select one input from:

a) 2^n inputs

b) n inputs

c) 2 inputs

d) n^2 inputs

Answer: a) 2^n inputs

### A demultiplexer with n select lines can distribute data from one input line to:

a) 2^n output lines

b) n output lines

c) 2 output lines

d) n^2 output lines

Answer: a) 2^n output lines

### A 3-to-8 decoder has how many output lines?

a) 3

b) 4

c) 8

d) 10

Answer: c) 8

### A 4-to-2 priority encoder has how many output lines?

a) 2

b) 3

c) 4

d) 5

Answer: a) 2

### How many inputs does an 8-to-3 encoder have?

a) 2

b) 3

c) 8

d) 10

Answer: c) 8

### A BCD-to-7 segment decoder has how many output lines?

a) 2

b) 3

c) 4

d) 7

Answer: d) 7

### A 4-bit magnitude comparator has how many output lines?

a) 1

b) 2

c) 3

d) 4

Answer: c) 3

### In a 4-bit binary subtractor, the inputs are:

a) Two 4-bit binary numbers and a borrow-in

b) Two 4-bit binary numbers without a borrow-in

c) Three 4-bit binary numbers and a borrow-in

d) Three 4-bit binary numbers without a borrow-in

Answer: a) Two 4-bit binary numbers and a borrow-in

### The output of a binary subtractor is the:

a) Sum of two binary numbers

b) Difference of two binary numbers

c) Product of two binary numbers

d) Quotient of two binary numbers

Answer: b) Difference of two binary numbers

### In a 4-to-2 priority encoder, the highest priority input is represented by:

a) The highest binary value

b) The lowest binary value

c) The middle binary value

d) Any arbitrary binary value

Answer: a) The highest binary value

### The main building blocks of combinational circuits are:

a) Flip-flops

b) Counters

c) Logic gates

d) Memory units

Answer: c) Logic gates

### In a combinational circuit, the output is a function of:

a) Input and time

b) Output and time

c) Input and output

d) Input, output, and time

Answer: c) Input and output