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Digital Circuits Multiple-Choice Questions (MCQs)

Digital circuits is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them.

Digital Circuits MCQs: This section contains multiple-choice questions and answers on the various topics of Digital Circuits. Practice these MCQs to test and enhance your skills on Digital Circuits.

List of Digital Circuits MCQs

1. What is the base of the decimal number system?

1. 2
2. 8
3. 10
4. 16

Answer: C) 10

Explanation:

The base of the decimal number system is 10.

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2. What is the range of the decimal number system?

1. 1-10
2. 0-10
3. 0-9

Answer: C) 0-9

Explanation:

The range of the decimal number system is 10.

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3. Integer part is the part that lies to the ____ of the decimal point in the Decimal number system.

1. Right
2. Left

Answer: B) Left

Explanation:

The integer part is the part that lies to the left of the decimal point in the Decimal number system.

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4. The ____ component is the part of the number to the right of the decimal point.

1. Fractional
2. Integer

Answer: A) Fractional

Explanation:

The Fractional component is the part of the number to the right of the decimal point.

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5. What of the following is the correct representation of a decimal number system?

1. 192.146 = (1 × 10²) + (9 × 10¹) + (2 × 10⁰) + (1 × 10^-1) + (4 × 10^-2) + (6 × 10^-3)
2. 192.146 = (1 × 10³) + (9 × 10²) + (2 × 10¹) + (1 × 10^-1) + (4 × 10^-2) + (6 × 10^-3)
3. 192.146 = (1 × 10¹) + (9 × 10²) + (2 × 10³) + (1 × 10^-1) + (4 × 10^-2) + (6 × 10^-3)
4. None

Answer: A) 192.146 = (1 × 10²) + (9 × 10¹) + (2 × 10⁰) + (1 × 10^-1) + (4 × 10^-2) + (6 × 10^-3)

Explanation:

192.146 = (1 × 10²) + (9 × 10¹) + (2 × 10⁰) + (1 × 10^-1) + (4 × 10^-2) + (6 × 10^-3) is the correct answer.

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6. What is the base number of the binary number system?

1. 2
2. 4
3. 6
4. 8

Answer: A) 2

Explanation:

The base of the binary number system is 2.

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7. What is the range of numbers used in a binary number system?

1. 0-2
2. 0-1
3. 1-2
4. None

Answer: B) 0-1

Explanation:

O and 1 numbers are used in the binary number system.

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8. What is the base of the Octal number system?

1. 2
2. 4
3. 8
4. 16
5. 10

Answer: C) 8

Explanation:

The base of the Octal number system is 8.

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9. What range of numbers are used in the octal number system?

1. 0-8
2. 1-9
3. 0-9
4. 0-7

Answer: D) 0-7

Explanation:

From 0 to 7 numbers are used in the octal number system.

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10. What is the base of the hexadecimal number system?

1. 10
2. 16
3. 20
4. 18

Answer: B) 16

Explanation:

The base of the hexadecimal number system is = 6.

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11. What is the range of the hexadecimal number system?

1. 0 to 10 and A to F
2. 0 to 9 and A to F
3. 1-10 and A to E
4. 0-9 and A to E

Answer: B) 0 to 9 and A to F

Explanation:

The range of the hexadecimal number system is: 0 to 9 and A to F.

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12. All unsigned numbers are ____.

1. Positive
2. Negative

Answer: A) Positive

Explanation:

All unsigned numbers are positive.

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13. What is the full form of MSB?

1. Main significant bit
2. Minimum significant bit
3. Most significant bit

Answer: C) Most significant bit

Explanation:

MSB stands for the most significant bit.

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14. MSB of signed binary numbers is also known as ____.

1. Most bit
2. Min bit
3. Signed bit
4. Sign bit

Answer: D) Sign bit

Explanation:

MSB of signed binary numbers is also known as the sign bit.

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15. How many types of representation are there for signed binary numbers?

1. 5
2. 4
3. 3
4. 2

Answer: C) 3

Explanation:

There are three types of representations for signed binary numbers:

• Sign-Magnitude form
• 1's complement form
• 2's complement form

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16. 1's complement of positive number gives a ____ number.

1. Positive number
2. Negative number
3. Both

Answer: B) Negative number

Explanation:

1's complement of a positive number gives a negative number.

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17. 1's complement of negative number gives a ____ number.

1. Positive
2. Negative
3. Original signed binary number

Answer: A) Positive

Explanation:

1's complement of a negative number gives a positive number.

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18. If you do two times the one's complement of a binary number including the sign bit, what result you would get?

1. Positive
2. Negative
3. Original signed binary number

Answer: C) Original signed binary number

Explanation:

If you do two times the one's complement of a binary number including the sign bit, you will get the original signed binary number.

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19. The 2's complement of positive number gives a ____ number?

1. Negative number
2. Positive number

Answer: A) Negative number

Explanation:

The 2's complement of a positive number gives a negative number.

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20. What will be the 1's complement of 50 in binary number?

1. 110010
2. 001101
3. 110110

Answer: C) 110110

Explanation:

First step is to convert the decimal 50 into binary which is equal to 110010, now to find the 1's complement just replace 0 with 1 therefore the final answer is = 001101.

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21. What will be the 1's complement of 30 in binary number?

1. 11110
2. 00000
3. 11111
4. 00001

Answer: D) 00001

Explanation:

First step is to convert decimal 30 to binary i.e., 11110, now just change the value of 0 to 1 and 1 to 0 therefore the final answer is = 00001.

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22. Binary codes are classified into how many types?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

Binary codes are classified into 2 types:

• Weighted codes
• Unweighted codes

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23. Weighted codes are classified into how many types?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

Weighted codes are classified into 2 types: positively weighted codes and negatively weighted codes.

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24. What is the full form of BCD?

1. Base decimal code
2. Binary dialogue code
3. Binary coded decimal
4. Base-coded decimal

Answer: C) Binary coded decimal

Explanation:

BCD stands for binary coded decimal.

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25. How many types of parity codes are there?

1. 5
2. 4
3. 2
4. 1

Answer: C) 2

Explanation:

There are two types of parity codes: Even parity code and odd parity code.

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26. The value of an even parity bit should be ____ if an even number of ones is present in the binary code.

1. 0
2. 1

Answer: A) 0

Explanation:

If the binary code has an even number of ones, the value of the even parity bit should be zero.

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27. Even parity bit is used only for ____.

1. Error detection
2. Error correction

Answer: A) Error detection

Explanation:

Even parity bit is used only for Error detection.

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28. The value of the odd parity bit should be ____ if an odd number of ones is present in the binary code.

1. 0
2. 1

Answer: A) 0

Explanation:

If there are an odd number of ones in the binary code, the value of the odd parity bit should be zero.

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29. Hamming code is used for ____.

1. Error detection
2. Error correction
3. None
4. Both

Answer: D) Both

Explanation:

Hamming code is used for Error detection and Error correction.

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30. Which of the following theorem is used to find the complement of the Boolean function?

1. Duality theorem
2. DeMorgan's theorem

Answer: B) DeMorgan's theorem

Explanation:

DeMorgan's theorem is used to find the complement of a Boolean function.

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31. What do you mean by Canonical SoP?

1. Canonical sum of products
2. Canonical solution of problems
3. Canonical solution of products

Answer: A) Canonical sum of products

Explanation:

Canonical SoP stands for Canonical sum of products.

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32. Canonical SoP form is also known as ____.

1. Sum of Max terms
2. Sum of Min terms

Answer: B) Sum of Min terms

Explanation:

Canonical SoP form is also known as the Sum of min terms form.

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33. Canonical PoS form is also known as ____.

1. Product of Max terms
2. Sum of Max terms
3. Product of Min terms
4. Sum of Min terms

Answer: A) Product of Max terms

Explanation:

Canonical PoS is also known as Product of Max terms.

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34. What is the number of cells in 3 variable K-map?

1. 5
2. 2
3. 6
4. 8

Answer: D) 8

Explanation:

There are 8 cells in 3 variable K-map.

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35. What is the number of cells in 2 variable K-map?

1. 4
2. 2
3. 6
4. 8

Answer: A) 4

Explanation:

There are 4 cells in 2 variable K-map.

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36. What is the number of cells in 4 variable K-map?

1. 32
2. 16
3. 20
4. 14

Answer: B) 16

Explanation:

There are 16 cells in 4 variable K-map.

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37. What is the number of cells in 5 variable K-map?

1. 40
2. 24
3. 32
4. 20
5. 14

Answer: C) 32

Explanation:

There are 32 cells in 5 variable K-map.

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38. Ex-OR and Ex-NOR gate comes under which category of the gate?

1. Basic gate
2. Special gate
3. Universal gate

Answer: B) Special gate

Explanation:

Ex-OR and Ex-NOR gate comes under the category of special gate.

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39. Which of the following is the universal gate?

1. NAND
2. NOR
3. Both
4. None

Answer: C) Both

Explanation:

NAND and NOR both come under the category of universal gate.

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40. ____ form is used when the output of a two-level logic realization cannot be achieved using a single logic gate.

1. Non-degenerative
2. Degenerative

Answer: A) Non-degenerative

Explanation:

Non-degenerative form is used when the output of a two-level logic realization cannot be achieved using a single logic gate.

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41. Octal to binary encoder has how many inputs?

1. 2
2. 8
3. 16
4. 1

Answer: B) 8

Explanation:

Octal to binary encoder has 8 inputs.

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42. A 4*1 mux has how many inputs?

1. 5
2. 4
3. 2
4. 1

Answer: B) 4

Explanation:

4*1 mux has 4 data inputs, two selection lines, and one output.

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43. What do you mean by PLDs?

1. Programmable Logic devices
2. Perfect Logic devices
3. Prune Logic devices
4. Personal Logic devices

Answer: A) Programmable Logic devices

Explanation:

PLDs are known as Programmable Logic devices. These are the integrated circuits.

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44. How many types of PLDs are there based on the types of arrays?

1. 5
2. 4
3. 3
4. 2

Answer: C) 3

Explanation:

On the basis of type of array there are 3 kinds of PLDs:

• Programmable Read Only Memory
• Programmable Array Logic
• Programmable Logic Array

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45. Which of the following statement is correct?

1. PROMs are programmable logic devices with fixed AND and programmable OR arrays
2. PROMs are programmable logic devices with fixed NAND and programmable OR arrays
3. PROMs are programmable logic devices with fixed NOR and programmable OR arrays

Answer: A) PROMs are programmable logic devices with fixed AND and programmable OR arrays.

Explanation:

PROMs are programmable logic devices with fixed AND and programmable OR arrays.

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46. Which of the following statement is TRUE about PAL (Programmable array logic)?

1. PAL is a programmable logic device with a fixed NOR array and a programmable OR array
2. PAL is a programmable logic device with a fixed AND array and a programmable NOR array
3. PAL is a programmable logic device with a fixed OR array and a programmable AND array

Answer: C) PAL is a programmable logic device with a fixed OR array and a programmable AND array.

Explanation:

PAL is a programmable logic device with a fixed OR array and a programmable AND array.

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47. PAL's outputs will be in the form of a ____.

1. Product of sum
2. Sum of products

Answer: B) Sum of products

Explanation:

PAL's outputs will be in the form of a sum of products.

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48. The threshold gate has how many inputs and outputs?

1. At least one output and only one input
2. At least one input and only one output
3. Any number of output and inputs

Answer: B) At least one input and only one output.

Explanation:

The threshold gate has at least one input and only one output.

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49. How do you represent the threshold gate?

1. Via circle
2. Via Square
3. Via Combinational circuit
4. None

Answer: A) Via circle

Explanation:

A circle represents a threshold gate.

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50. Which of the following statement is correct about the combinational and Sequential circuit?

1. In sequential circuits Only the current inputs determine the outputs, and in combinational circuits, Outputs are determined by both the current inputs and the current state
2. In combinational circuits, Only the current inputs determine the outputs and in sequential circuits, Outputs are determined by both the current inputs and the current state

Answer: B) In combinational circuits, Only the current inputs determine the outputs and in sequential circuits, Outputs are determined by both the current inputs and the current state.

Explanation:

In combinational circuits, Only the current inputs determine the outputs and in sequential circuits, Outputs are determined by both the current inputs and the current state.

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51. Among combinational and sequential circuits in which of the following feedback is not present?

1. Combinational Circuits
2. Sequential Circuits

Answer: A) Combinational Circuits

Explanation:

In combinational circuits, feedback is not present.

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52. How many types of sequential circuits are there?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

There are two types of sequential circuits:

• Asynchronous sequential circuits
• Synchronous Sequential circuits

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53. If all of the outputs of a sequential circuit change in response to the active transition of the clock signal, the sequential circuit is said to be ____.

1. Asynchronous
2. Synchronous

Answer: B) Synchronous

Explanation:

If all of the outputs of a sequential circuit change in response to the active transition of the clock signal, the sequential circuit is said to be synchronous.

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54. How many types of triggers are used in sequential circuits?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

Two types of triggers are used in sequential circuits:

• Level triggering
• Edge Triggering

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55. How many types of level triggering are there?

1. 2
2. 3
3. 4
4. 5

Answer: A) 2

Explanation:

There are two types of level triggering:

• Positive level triggering
• Negative level triggering

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56. ____ level triggering occurs when the sequential circuit is operated with the clock signal while it is in Logic High.

1. Positive level triggering
2. Negative level triggering

Answer: A) Positive level triggering

Explanation:

Positive level triggering occurs when the sequential circuit is operated with the clock signal while it is in Logic High.

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57. How many types of edge triggering are there based on the transitions of the clock signal?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

There are two types of edge triggering based on the transitions of clock signal:

• Positive level triggering
• Negative level triggering

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58. What is the full form of the SR latch?

1. Set Reset Latch
2. Set Remind Latch
3. Save Reset Latch

Answer: A) Set Reset Latch

Explanation:

SR latch stands for Set reset latch.

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59. Which of the following is the drawback of the SR latch?

1. When both S and R are zero, the next state value cannot be predicted
2. When both S and R are one, the next state value cannot be predicted
3. When both S and R are one, the next state value can be predicted

Answer: B) When both S and R are one, the next state value cannot be predicted.

Explanation:

SR latch has a drawback i.e., When both S and R are one, the next state value cannot be predicted.

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60. What is the full form of a D latch?

1. Datagram latch
2. Dataset latch
3. Database latch
4. Data latch

Answer: D) Data latch

Explanation:

Full form of the D latch is the Data latch.

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61. Which of the following is the simplest version of the JK flipflop?

1. T flip-flop
2. SR flip-flop
3. D flip-flop

Answer: A) T flip-flop

Explanation:

T flip-flop is the simplest version of JK flip-flop.

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62. The ____ is a collection of flip-flops that are used to store binary data.

1. Log
2. Database
3. Ledger
4. Register

Answer: D) Register

Explanation:

The register is a collection of flip-flops that are used to store binary data.

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63. The register is known as a ____- register if it is capable of moving bits either to the right or to the left.

1. Flag
2. Shift
3. Accumulator
4. Stack

Answer: B) Shift

Explanation:

The register is known as a shift register if it is capable of moving bits either to the right or to the left.

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64. An 'N' bit shift register contains ____ flip-flops.

1. N-1
2. N+1
3. N
4. N2

Answer: C) N

Explanation:

An 'N' bit shift register contains 'N' flip-flops.

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65. ____ shift register is a shift register that accepts serial input and outputs serial output.

1. SISO
2. SIPO
3. PISO
4. PIPO

Answer: A) SISO

Explanation:

Serial In - Serial Out SISO shift register is a shift register that accepts serial input and outputs serial output.

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66. Shift registers are used as ____.

1. Parallel to serial converter
2. Serial to parallel converter
3. Sequence generator
4. Counters
5. All of the above

Answer: E) All of the above

Explanation:

Shift registers are used as:

• Parallel to serial converter
• Serial to parallel converter
• Sequence generator
• Counters

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67. When a counter counts from 0 to 2N -1, it is referred to as a ____ counter.

1. Binary down counter
2. Binary up counter

Answer: B) Binary up counter

Explanation:

When a counter counts from 0 to 2N- 1, it is referred to as a binary up counter.

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68. How many types of counters are there based on the flip-flops?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

There are two types of counters based on the flip flops:

• Asynchronous counter
• Synchronous counter

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69. If the flip-flops do not receive the same clock signal, the counter is referred to as ____.

1. Asynchronous
2. Synchronous

Answer: A) Asynchronous

Explanation:

If the flip-flops do not receive the same clock signal, the counter is referred to as asynchronous.

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70. The synchronous sequential circuits is also known as ____.

1. Finite state machine
2. Regular expression
3. Grammar

Answer: A) Finite state machine

Explanation:

Synchronous sequential circuits is also known as Finite state machine.

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71. How many types of Finite state machines are there?

1. 5
2. 4
3. 3
4. 2

Answer: D) 2

Explanation:

There are two types of FSM:

• Mealy state machine
• Moore state machine

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72. A ____ machine is a finite state machine in which the current state and current input symbol determine the future state.

1. Moore
2. Mealy

Answer: A) Moore

Explanation:

A Moore machine is a finite-state machine in which the current state and current input symbol determine the future state.

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73. What is the Mealy machine?

1. A Mealy machine is a machine in which the output symbol depends upon the present input symbol and the present state of the machine
2. A Mealy machine is a machine in which the output symbol depends upon the present input symbol and the next state of the machine
3. A Mealy machine is a machine in which the output symbol depends upon the next input symbol and the next state of the machine
4. A Mealy machine is a machine in which the output symbol depends upon the next input symbol and the present state of the machine

Answer: A) A Mealy machine is a machine in which the output symbol depends upon the present input symbol and the present state of the machine.

Explanation:

A Mealy machine is a machine in which the output symbol depends upon the present input symbol and the present state of the machine.

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74. What do you mean by ASM charts?

1. Algorithmic state machine
2. Altar state machine
3. Algo state machine

Answer: A) Algorithmic state machine

Explanation:

ASM stands for Algorithmic state machine.

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75. In ASM charts state box is represented in which shape?

1. Oval
2. Cube
3. Triangle
4. Rectangular

Answer: D) Rectangular

Explanation:

In ASM charts state box is represented in a rectangular shape.

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76. In ASM charts decision box is represented in which shape?

1. Oval
2. Cube
3. Triangle
4. Diamond

Answer: D) Diamond

Explanation:

In ASM charts decision box is represented in a diamond shape.

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77. In ASM charts conditional output box is represented in which shape?

1. Oval
2. Cube
3. Triangle
4. Square

Answer: A) Oval

Explanation:

In ASM charts conditional output box is represented in an oval shape.

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