CS and IT GATE 2015 Set-1 Questions with Answer

Ques 1 Automata

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. L₁' ∪ L₂ is recursively enumerable

I only

III only

III and IV only

I and IV only

Ques 2 C Programming

The output of the following C program is __________.

void f1 (int a, int b)
{
int c;
c=a; a=b; b=c;
}
void f2 (int *a, int *b)
{
int c;
c=*a; *a=*b;*b=c;
}
int main()
{
int a=4, b=5, c=6;
f1(a, b);
f2(&b, &c);
printf (“%d”, c-a-b);
return 0;
}

a is the correct answer.

Ques 3 C Programming

Which of 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.

II only

I only

I and IV only

III and IV only

Ques 4 COA

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_________

a is the correct answer.

Ques 5 COA

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

Either S₁ or S₂

Either S₂ or ₃

Only S₂ and ₃

All of S₁, S₂ and S₃

Ques 6 Compiler Design

Which one of the following is True at any valid state in shift-reduce parsing?

Viable prefixes appear only at the bottom of the stack and not inside

Viable prefixes appear only at the top of the stack and not inside

The stack contains only a set of viable prefixes

The stack never contains viable prefixes

Ques 7 Compiler Design

A variable x is said to be live at a statement S_i in a program if the following three conditions hold simultaneously:
i. There exists a statement S_j that uses x
ii. There is a path from S_i to S_j in the flow graph corresponding to the program
iii. The path has no intervening assignment to x including at S_i and S_j

The variables which are live both at the statement in basic block 2 and at the statement in basic block 3 of the above control flow graph are

p, s, u

r, s, u

r, u

q, v

Ques 8 Compiler Design

The least number of temporary variables required to create a three-address code in static single assignment form for the expression q + r / 3 + s - t * 5 + u * v / w is _______.

Ques 9 Computer Network

Consider a LAN with four nodes S₁, S₂, S₃ and S₄. Time is divided into fixed-size slots, and a node can begin its transmission only at the beginning of a slot. A collision is said to have occurred if more than one node transmit in the same slot. The probabilities of generation of a frame in a time slot by S₁, S₂, S₃ and S₄ are 0.1, 0.2, 0.3 and 0.4, respectively. The probability of sending a frame in the first slot without any collision by any of these four stations is_________

a is the correct answer.

Ques 10 Computer Network

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 is the correct answer.

Ques 11 Computer Network

Which one of the following fields of an IP header is NOT modified by a typical IP router?

Checksum

Source address

Time to Live (TTL)

Length

Ques 12 Computer Network

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

N(N – 1)

N(N – 1)/2

(N – 1)²

Ques 13 Computer Network

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?

HTTP, FTP

HTTP, TELNET

FTP, SMTP

HTTP, SMTP

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CS and IT GATE 2015 Set-1 Questions with Answer