Friday, 28 October 2016

UGC Net Computer Science Paper 3 July-16 Page 6

51. Which of the following information about the UNIX file system is not correct ?
(1) Super block contains the number of i-nodes, the number of disk blocks, and the start
of the list of free disk blocks.
(2) An i-node contains accounting information as well as enough information to locate
all the disk blocks that holds the file’s data.
(3) Each i-node is 256-bytes long.
(4) All the files and directories are stored in data blocks.

Answer C
Explanation : 

The default bytes per inode is approximately 16384. If you're running out of inodes, you might try for
example:mkfs.ext4 -i 8192 /dev/mapper/main-var2

52. Which of the following option with reference to UNIX operating system is not correct ?
(1) INT signal is sent by the terminal driver when one types <Control-C> and it is a
request to terminate the current operation.
(2) TERM is a request to terminate execution completely. The receiving process will
clean up its state and exit.
(3) QUIT is similar to TERM, except that it defaults to producing a core dump if not
caught.
(4) KILL is a blockable signal.

Answer D
Explanation : 

SIGINT
SIGTERM
SIGQUIT
SIGKILL
The SIGINT signal is sent to a process by its controlling terminal when a user wishes to interrupt the process. This is typically initiated by pressing Ctrl+C., but on some systems, the "delete" character or "break" key can be used. The SIGTERM signal is sent to a process to request its termination. Unlike the SIGKILL signal, it can be caught and interpreted or ignored by the process. This allows the process to perform nice termination releasing resources and saving state if appropriate. SIGINT is nearly identical to SIGTERM. The SIGQUIT signal is sent to a process by its controlling terminal when the user requests that the process quit and perform a core dump.

The SIGKILL signal is sent to a process to cause it to terminate immediately (kill). In contrast to SIGTERM and SIGINT, this signal cannot be caught or ignored, and the receiving process cannot perform any clean-up upon receiving this signal.

Dump


In computing, a core dump (in Unix parlance), memory dump, or system dump consists of the recorded state of the working memory of a computer program at a specific time, generally when the program has crashed or otherwise terminated abnormally. In practice, other key pieces of program state are usually dumped at the same time, including the processor registers, which may include the program counter and stack pointer, memory management information, and other processor and operating system flags and information. Core dumps are often used to assist in diagnosing and debugging errors in computer programs.

53. A multicomputer with 256 CPUs is organized as 16 × 16 grid. What is the worst case
delay (in hops) that a message might have to take ?
(1) 16
(2) 15
(3) 32
 (4) 30

54. Suppose that the time to do a null remote procedure call (RPC) (i.e. 0 data bytes) is
1.0 msec, with an additional 1.5 msec for every 1K of data. How long does it take to read
32 K from the file server as 32 1K RPCs ?
(1) 49 msec
 (2) 80 msec
(3) 48 msec
 (4) 100 msec

55. Let L be the language generated by regular expression 0*10* and accepted by the
deterministic finite automata M. Consider the relation RM defined by M. As all states are
reachable from the start state, RM has _____ equivalence classes.
(1) 2
(2) 4
(3) 5
(4) 6

56. Let L = {0n1n|n ≥ 0} be a context free language.
Which of the following is correct ?
(1) –L is context free and Lk is not context free for any k ≥ 1.
(2) –L is not context free and Lk is context free for any k ≥ 1.
(3) Both –L and Lk is for any k ≥ 1 are context free.
(4) Both –L and Lk is for any k ≥ 1 are not context free.

57. Given a Turing Machine
M = ({q0, q1, q2, q3}, {a, b}, {a, b, B}, δ, B, {q3})
Where δ is a transition function defined as
δ(q0, a) = (q1, a, R)
δ(q1, b) = (q2, b, R)
δ(q2, a) = (q2, a, R)
δ(q2, b) = (q3, b, R)
The language L(M) accepted by the Turing Machine is given as :
(1) aa*b
(2) abab
(3) aba*b
(4) aba*

58. Consider a discrete memoryless channel and assume that H(x) is the amount of
information per symbol at the input of the channel; H(y) is the amount of information per
symbol at the output of the channel; H(x|y) is the amount of uncertainty remaining on x
knowing y; and I (x; y) is the information transmission.
Which of the following does not define the channel capacity of a discrete memoryless
channel ?
(1) max I (x; y)
(2) max [H(y) – H(y|x)]
p(x) p(x)
(3) max [H(x) – H(x|y)]
 (4) max H(x|y)
p(x) p(x)

59. Consider a source with symbols A, B, C, D with probabilities 1/2, 1/4, 1/8, 1/8
respectively. What is the average number of bits per symbol for the Huffman code
generated from above information ?
(1) 2 bits per symbol
(2) 1.75 bits per symbol
(3) 1.50 bits per symbol
 (4) 1.25 bits per symbol

60. Which of the following is used for the boundary representation of an image object ?
(1) Quad Tree
 (2) Projections
(3) Run length coding
(4) Chain codes

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