GATE Computer Science and IT Solved Paper 2015 Session 1 - Part 3

21.       Consider a 4-bit Johnson counter with an initial value of 0000. The counting sequence of this counter is
(A) 0, 1, 3, 7, 15, 14, 12, 8, 0
(B) 0, 1, 3, 5, 7, 9, 11, 13, 15, 0
(C) 0, 2, 4, 6, 8, 10, 12, 14, 0
(D) 0, 8, 12, 14, 15, 7, 3, 1, 0
Answer: D
22.       For computers based on three-address instruction formats, each address field can be used to specify which of the following:
(S1) A memory operand
(S2) A processor register
(S3) An implied accumulator register
(A) Either S1 or S2                  (B) Either S2 or S3
(C) Only S2 and S3                 (D) All of S1, S2 and S3
Answer: A
23.       Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are FALSE with respect to the TCP connection?
I. If the sequence number of a segment is m, then the sequence number of the subsequent segment is always m+1.
II. If the estimated round trip time at any given point of time is t sec, the value of the retransmission timeout is always set to greater than or equal to t sec.
III. The size of the advertised window never changes during the course of the TCP connection.
IV. The number of unacknowledged bytes at the sender is always less than or equal to the advertised window.
(A) III only                      (B) I and III only
(C) I and IV only           (D) II and IV only
Answer: B
24.       Suppose that everyone in a group of N people wants to communicate secretly with the N-1 others using symmetric key cryptographic system. The communication between any two persons should not be decodable by the others in the group. The number of keys required in the system as a whole to satisfy the confidentiality requirement is
(A) 2N                (B) N(N-1)
(C) N(N-1)/2      (D) (N-1)2
Answer: C
25.       Which of the following statements is/are FALSE?
I. XML overcomes the limitations in HTML to support a structured way of organizing content.
II. XML specification is not case sensitive while HTML specification is case sensitive.
III. XML supports user defined tags while HTML uses pre-defined tags.
IV. XML tags need not be closed while HTML tags must be closed.
(A) II only                       (B) I only
(C) II and IV only                      (D) III and IV only
Answer: C

26.       Which one of the following fields of an IP header is NOT modified by a typical IP router?
(A) Checksum              (B) Source address
(C) Time to Live (TTL) (D) Length
Answer: B
27.       In one of the pairs of protocols given below, both the protocols can use multiple TCP connections between the same client and the server. Which one is that?
(A) HTTP, FTP              (B) HTTP, TELNET
(C) FTP, SMTP             (D) HTTP, SMTP
Answer: A
28.       For any two languages L1 and L2 such that L1 is context-free and L2 is recursively enumerable but not recursive, which of the following is/are necessarily true?
I. L1’ (complement of L1) is recursive
II. L2’ (complement of L2) is recursive
III. L1’ is context-free
IV. L1L2 is recursively enumerable
(A) I only                        (B) III only
(C) III and IV only         (D) I and IV only
Answer: D
29.       Consider a system with byte-addressable memory, 32-bit logical addresses, 4 kilobyte page size and page table entries of 4 bytes each. The size of the page table in the system in megabytes is ................
Answer: 4
30.    The following two functions P1 and P2 that share a variable B with an initial value of 2 execute concurrently.
P1( )       {                                   P2( )    {
C = B – 1;                               D = 2 * B;
B = 2 * C;                               B = D - 1;
}                                                  }
The number of distinct values that B can possibly take after the execution is ...............
Answer: 3

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