PSC HSST Computer Science Model Questions and Answers – Part 4

51. Graph having every pair of vertices connected is called:
(A) Cycle graph (B) Complete graph
(C) Peterson graph (D) Is a Tree
Answer: B

52. The Eigen vectors of a real symmetric matrix corresponding to different Eigen values are:
(A) Orthogonal matrix (B) Singular matrix
(C) Non-singular matrix (D) Inverse matrix
Answer: A

53. The system of equations 4x+6y=8, 3x+2y=1, 7x+8y=9 has:
(A) only one solution (B) infinite solutions
(C) two solutions (D) none of these
Answer: C

54. The Eigen values of the square matrix are:
(A) positive (B) imaginary
(C) real (D) negative
Answer: C

55. The Equations will have:
(A) no unique solution (B) only one solution
(C) has only two solutions (D) has infinite
Answer: Question not complete.

56. Which is fastest?
(A) DTL (B) TTL
(C) ECL (D) CMOS
Answer: C

57. Which is commutative but not associative?
(A) NOT (B) NOR
(C) XOR (D) NAND
Answer: B, D
Explanation:
NAND and NOR operations are commutative, but not associative.
(x↓y)↓z ≠ x↓(y↓z) (↓ = NOR operation)
(x↑y)↑z ≠ x↑(y↑z) (↑ = NAND operation)

58. Which is Universal gate?
(A) AND (B) NOR
(C) XOR (D) NOT
Answer: B
Explanation:
A universal gate is one from which all other basic gates can be formed. NAND and NOR are Universal gates.

59. How many NAND gates are needed to perform X.Y?
(A) 3 (B) 4
(C) 2 (D) 1
Answer: Invalid Question
Explanation: If the question was the minimum NAND gates required to perform X.Y the answer will be C (2).

60. Which is non-volatile?
(A) RAM (B) PROM
(C) EPROM (D) ROM
Answer: D

61. Which is the access method to take data from tape memory?
(A) Direct (B) Sequential
(C) Parallel (D) Serial
Answer: B

62. The cycle time for a memory system is:
(A) access time (B) longer than access time
(C) less than access time (D) sub multiple of access time
Answer: B

63. How many RAM chips are needed to generate the (256K X 1 bit)?
(A) 8 (B) 12
(C) 32 (D) 64
Answer: C

64. T flip-flops are generally used for:
(A) counter (B) delay switch
(C) counter and frequency divider (D) decoder
Answer: C

65. Register used as working area in CPU is:
(A) Program counter (B) Stack
(C) Instruction register (D) Accumulator
Answer: D

66. A microprocessor can be:
(A) Programmable (B) Non Programmable
(C) Micro programmable (D) All of the above
Answer: D

67. Which is 16 bit microprocessor?
(A) Z 80 (B) Motorola 6800
(C) Intel 8086 (D) Intel 80486
Answer: C

68. “n” flip-flops will divide the frequency into a factor of:
(A) n (B) 1/n
(C) 2 to the power of ‘n’ (D) log(n)
Answer: C

69. 8 2 4 1 is the:
(A) BCD code (B) Gray code
(C) Excess -3 code (D) ASCII code
Answer: 8421 is BCD code.
Explanation:
BCD Code is 8421 (not 8241). Excess-3 and gray code are non-weighted codes.

70. (1001000010011001) base 2; equivalent in base 16 is:
(A) 9899 (B) 9989
(C) 8999 (D) 9999
Answer: Correct answer is 9099
Explanation:
An easy way to convert from binary to hexadecimal is to group binary digits into sets of four, starting with the least significant (rightmost) digits. Pad the most significant digits with zeros if necessary to complete a group of four. Here 1001000010011001 is grouped as 1001, 0000, 1001, 1001. Decimal equivalent of each group is 9 0 9 9. Hence 9099 base 16 is the answer.

71. Which is a programmable interval timer?
(A) 8253 (B) NE 555
(C) 8275 (D) 8251
Answer: A

72. Negative number cannot be represented in:
(A) Signed magnitude form (B) 1’s complement form
(C) 2’s complement form (D) None of the above forms
Answer: D

73. Which of the following interrupt is both level and edge sensitive?
(A) RST 5.5 (B) INTER
(C) TRAP (D) RST 7.5
Answer: C

74. What is a BUFFER?
(A) Convert input data to output
(B) CPU stores program counter
(C) An Interphase between CPU and peripheral
(D) Convert program to EXE form
Answer: C

75. By default any real number in C is represented as:
(A) a float (B) a double
(C) a long double (D) long float
Answer: B