Computer Science Study Materials for Competitive Exams

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Thursday, 29 September 2016

CBSE UGC NET Computer Science Paper III August 2016 (Re-test) - Part 6

51.       An operating system supports a paged virtual memory, using a central processor with a cycle time of one microsecond. It costs an additional one microsecond to access a page other than the current one. Pages have 1000 words, and the paging device is a drum that rotates at 3000 revolutions per minute and transfers one million words per second. Further, one percent of all instructions executed accessed a page other than the current page. The instruction that accessed another page, 80% accessed a page already in memory and when a new page was required, the replaced page was modified 50% of the time. What is the effective access time on this system, assuming that the system is running only one process and the processor is idle during drum transfers ?
(A) 30 microseconds               (B) 34 microseconds
(C) 60 microseconds               (D) 68 microseconds
Answer: B
52.       Consider the following page reference string :
1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6
Which of the following options, gives the correct number of page faults related to LRU, FIFO, and optimal page replacement algorithms respectively, assuming 05 page frames and all frames are initially empty ?
(A) 10, 14, 8      (B) 8, 10, 7
(C) 7, 10, 8        (D) 7, 10, 7
Answer: B
53.       Consider a file currently consisting of 50 blocks. Assume that the file control block and the index block is already in memory. If a block is added at the end (and the block information to be added is stored in memory), then how many disk I/O operations are required for indexed (single-level) allocation strategy ?
(A) 1       (B) 101
(C) 27     (D) 0
Answer: A
54.       An experimental file server is up 75% of the time and down for 25% of the time due to bugs. How many times does this file server have to be replicated to give an availability of at least 99% ?
(A) 2       (B) 4
(C) 8       (D) 16
Answer: B
55.       Given the following two languages:
L1 = {uwwRn | u, v, w ϵ {a, b}+}
L2 = {uwwRn | u, v, w ϵ {a, b}+, |u| ≥ |v|}
Which of the following is correct ?
(A) L1 is regular language and L2 is not regular language.
(B) L1 is not regular language and L2 is regular language.
(C) Both L1 and L2 are regular languages.
(D) Both L1 and L2 are not regular languages.
Answer: A

56.       Given a Turing Machine
M = ({q0, q1}, {0, 1}, {0, 1, B}, δ, B, {q1})
Where δ is a transition function defined as
δ (q0, 0) = (q0, 0, R)
δ (q0, B) = (q1, B, R)
The language L(M) accepted by Turing machine is given as :
(A) 0* 1*             (B) 00*
(C) 10*               (D) 1*0*
Answer: B
57.       Let G = (V, T, S, P) be a context-free grammar such that every one of its productions is of the form A → n, with |v| = k > 1. The derivation tree for any string W ϵ L (G) has a height such that
Answer: D
58.       Which of the following is not used in standard JPEG image compression?
(A) Huffman coding    (B) Runlength encoding
(C) Zig-zag scan          (D) K-L Transform
Answer: D
59.       Which of the following is a source coding technique?
(A) Huffman coding                (B) Arithmetic coding
(C) Run-length coding           (D) DPCM
Answer: D
60.    If the histogram of an image is clustered towards origin on X-axis of a histogram plot then it indicates that the image is .............
(A) Dark             (B) Good contrast
(C) Bright          (D) Very low contrast
Answer: A

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