Digital electronics MCQ PDF

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Digital Electronics MCQ 17.06.2019

Digital Electronics MCQ by Ratnesh Sir 1. A code converter is a logic circuit that a) Inverts the given input b) Converts into decimal number c) Converts data of one type into another type d) None of the Mentioned 2. Use the weighting factors to convert the following BCD numbers to binary: 0101 0011 & 0010 0110 1000 a) 01010011 001001101000 b) 11010100 100001100000 c) 110101 100001100 d) 101011 001100001 3 The primary use for Gray code is a) Coded representation of a shaft’s mechanical position b) Turning on/off software switches c) To represent the correct ASCII code to indicate the angular position of a shaft on rotating machinery d) To convert the angular position of a shaft on rotating machinery into hexadecimal code 4. Why do we use gray codes? a) To count the no of bits changes b) To rotate a shaft c) Error correction d) None of the Mentioned 5. The binary representation of BCD number 00101001 (decimal 29) is a) 0011101 b) 0110101 c) 1101001 d) 0101011 6.

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Convert binary number into gray code: 100101 a) 101101 b) 001110 c) 110111 d) 111001 7. A binary digit is called a : (a) Bit (b) Byte (c) Number (d) Character 8. Which of the following is not a weighted code ? (a) Decimal Number system (b) Excess 3-code (c) Binary number System (d) None of these 9. The gray code equivalent of (1011) is : (a) 1101 (b) 1010 (c) 1110 (d) 1111 10. Number 85 in BCD code is : (a) 1000 1100 (b) 1101 1010 (c) 1000 0101 (d) 1101 1001 11. Excess-3 code is known as : (a) Weighted code (b) Cyclic redundancy code (c) Self-complementing code (d) Algebraic code 12. The binary equivalent of gray code 1110 is : (a) (1101) (b) (1011) (c) (1110)

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(d) (1111) 13. The binary equivalent of gray code 1111 is: (a) (1101) (b) (1011) (c) (1110) (d) (1010) 14. What is the excess-3 equivalent codes of (6) in 16-bit. (a) 0011001100011000 (b) 0011001100111001 (c) 0111001101011000 (d) 0111001101011200 15. What is the excess-3 equivalent codes of (78) in 16-bit. (a) 0011001110101011 (b) 0011001100111001 (c) 0111001101011000 (d) 0111001101011100 16. Binary coded decimal is a combination of __________ a) Two binary digits b) Three binary digits c) Four binary digits d) Five binary digits 17. The decimal number 10 is represented in its BCD form as __________ a) 10100000 b) 01010111 c) 00010000 d) 00101011 18. Add the two BCD numbers: 1001 + 0100 = ? a) 10101111 b) 01010000 c) 00010011 d) 00101011 19. Carry out BCD subtraction for (68) – (61) using 10’s complement method. a) 00000111

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b) 01110000 c) 100000111 d) 011111000 20. A three digit decimal number requires ________ for representation in the conventional BCD format. a) 3 bits b) 6 bits c) 12 bits d) 24 bits 21. The excess-3 code for 597 is given by __________ a) 100011001010 b) 100010100111 c) 010110010111 d) 010110101101 22. The decimal equivalent of the excess-3 number 110010100011.01110101 is _____________ a) 920.42 b) 1253.75 c) 861.75 d) 1132.87 23. What is a parity bit? a) An error detection is achieved by adding an extra bit b) After addition, the carry is found c) Bit generated during data transmission d) None of the Mentioned 24. The odd parity output of decimal number 9 is a) 0 b) 1 c) 1001 d) 0011 25. 1’s complement of 1011101 is a) 0101110 b) 1001101 c) 0100010 d) 1100101

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26. 2’s complement of 11001011 is a) 01010111 b) 11010100 c) 00110101 d) 11100010 27. On subtracting (01010)2 from (11110)2 using 1’s complement, we get a) -01001 b) -11010 c) -10101 d) -10100 28. On subtracting (010110)2 from (1011001)2 using 2’s complement, we get a) 0111001 b) 1100101 c) 0110110 d) 1000011 29. On subtracting (001100)2 from (101001)2 using 2’s complement, we get a) 1101100 b) 011101 c) 11010101 d) 11010111 30. On addition of 28 and 18 using 2’s complement, we get a) 00101110 b) 0101110 c) 00101111 d) 1001111 31. On addition of +38 and -20 using 2’s complement, we get a) 11110001 b) 100001110 c) 010010 d) 110101011 32. On addition of -46 and +28 using 2’s complement, we get a) -10010 b) -00101

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c) 01011 d) 0100101 33. On addition of -33 and -40 using 2’s complement, we get a) 1001110 b) -110101 c) 0110001 d) -1001001 34. On subtracting +28 from +29 using 2’s complement, we get a) 11111010 b) 111111001 c) 010101011 d) 1 35. 1’s complement can be easily obtained by using _________ a) Comparator b) Inverter c) Adder d) Subtractor 36. The advantage of 2’s complement system is that _________ a) Only one arithmetic operation is required b) Two arithmetic operations are required c) No arithmetic operations are required d) Different Arithmetic operations are required 37. For arithmetic operations only _________ a) 1’s complement is used b) 2’s complement c) 10’s complement d) 9’s complement 38. The addition of +19 and +43 results as _________ in 2’s complement system. a) 11001010 b) 101011010 c) 00101010 d) 0111110 39.

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There are ______ cells in a 4-variable K-map. a) 12 b) 16 c) 18 d) 8 40. The prime implicant which has at least one element that is not present in any other implicant is known as ___________ a) Essential Prime Implicant b) Implicant c) Complement d) Prime Complement 41. Don’t care conditions can be used for simplifying Boolean expressions in ___________ a) Registers b) Terms c) K-maps d) Latches 42. It should be kept in mind that don’t care terms should be used along with the terms that are present in ___________ a) Minterms b) Expressions c) K-Map d) Latches 43. There are many situations in logic design in which simplification of logic expression is possible in terms of XOR and _________________ operations. a) X-NOR b) XOR c) NOR d) NAND 44. These logic gates are widely used in _______________ design and therefore are available in IC form. a) Sampling b) Digital c) Analog d) Systems 45.

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A logic circuit that provides a HIGH output for both inputs HIGH or both inputs LOW is ____________ a) Ex-NOR gate b) OR gate c) Ex-OR gate d) NAND gate 46. How many basic binary subtraction operations are possible? a) 1 b) 4 c) 3 d) 2 47. The Boolean expression Y = (AB)’ is logically equivalent to what single gate? a) NAND b) NOR c) AND d) OR 48. Which combinational circuit is renowned for selecting a single input from multiple inputs & directing the binary information to output line? a) Data Selector b) Data distributor c) Both data selector and data distributor d) DeMultiplexer 49. What is the function of an enable input on a multiplexer chip? a) To apply Vcc b) To connect ground c) To active the entire chip d) To active one half of the chip 50. A digital multiplexer is a combinational circuit that selects ___________ a) One digital information from several sources and transmits the selected one b) Many digital information and convert them into one c) Many decimal inputs and transmits the selected information d) Many decimal outputs and accepts the selected information 51. In a multiplexer, the selection of a particular input line is controlled by ___________ a) Data controller b) Selected lines

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c) Logic gates d) Both data controller and selected lines 52. If the number of n selected input lines is equal to 2^m then it requires _____ select lines. a) 2 b) m c) n d) 2n 53. How many NOT gates are required for the construction of a 4-to-1 multiplexer? a) 3 b) 4 c) 2 d) 5 54. The enable input is also known as ___________ a) Select input b) Decoded input c) Strobe d) Sink 55. A combinational circuit that selects one from many inputs are ____________ a) Encoder b) Decoder c) Demultiplexer d) Multiplexer 56. Which of the following circuit can be used as parallel to serial converter? a) Multiplexer b) Demultiplexer c) Decoder d) Digital counter 57. A combinational circuit is one in which the output depends on the ____________ a) Input combination at the time b) Input combination and the previous output c) Input combination at that time and the previous input combination d) Present output and the previous output 58.

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The word demultiplex means ___________ a) One into many b) Many into one c) Distributor d) One into many as well as Distributor 59. Why is a demultiplexer called a data distributor? a) The input will be distributed to one of the outputs b) One of the inputs will be selected for the output c) The output will be distributed to one of the inputs d) Single input to Single Output 60. In a multiplexer the output depends on its ___________ a) Data inputs b) Select inputs c) Select outputs d) Enable pin 61. In 1-to-4 multiplexer, if C1 = 0 & C2 = 1, then the output will be ___________ a) Y0 b) Y1 c) Y2 d) Y3 62. In 1-to-4 multiplexer, if C1 = 1 & C2 = 1, then the output will be ___________ a) Y0 b) Y1 c) Y2 d) Y3 63. How many AND gates are required for a 1-to-8 demultiplexer? a) 2 b) 6 c) 8 d) 5 64. How many inputs will a decimal-to-BCD encoder have? a) 4 b) 8 c) 10

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d) 16 65. How many outputs will a decimal-to-BCD encoder have? a) 4 b) 8 c) 12 d) 16

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