Gate IT 2008

Question 61

Data transmitted on a link uses the following 2D parity scheme for error detection: Each sequence of 28 bits is arranged in a 4×7 matrix (rows r₀ through r₃, and columns d₇ through d₁) and is padded with a column d₀ and row r₄ of parity bits computed using the Even parity scheme. Each bit of column d₀ (respectively, row r₄) gives the parity of the corresponding row (respectively, column). These 40 bits are transmitted over the data link.

The table shows data received by a receiver and has n corrupted bits. What is the mini­mum possible value of n?

• 1
• 2
• 3
• 4

Question 62

Two popular routing algorithms are Distance Vector(DV) and Link State (LS) routing. Which of the following are true?
(S1) Count to infinity is a problem only with DV and not LS routing
(S2) In LS, the shortest path algorithm is run only at one node
(S3) In DV, the shortest path algorithm is run only at one node
(S4) DV requires lesser number of network messages than LS

• S1, S2 and S4 only
• S1, S3 and S4 only
• S2 and S3 only
• S1 and S4 only

Question 63

Which of the following statements are TRUE?
(S1) TCP handles both congestion and flow control
(S2) UDP handles congestion but not flow control
(S3) Fast retransmit deals with congestion but not flow control
(S4) Slow start mechanism deals with both congestion and flow control

• S1, S2 and S3 only
• S1 and S3 only
• S3 and S4 only
• S1, S3 and S4 only

Question 64

The three way handshake for TCP connection establishment is shown below. 

[caption width="800"] [/caption]

Which of the following statements are TRUE?
(S1) Loss of SYN + ACK from the server will not establish a connection
(S2) Loss of ACK from the client cannot establish the connection
(S3) The server moves LISTEN → SYN_RCVD → SYN_SENT → ESTABLISHED in the state machine on no packet loss 
(S4) The server moves LISTEN → SYN_RCVD → ESTABLISHED in the state machine on no packet loss.

• S2 and S3 only

• S1 and S4

• S1 and S3

• S2 and S4

Question 65

The total number of keys required for a set of n individuals to be able to communicate with each other using secret key and public key crypto-systems, respectively are:

• n(n-1) and 2n
• 2n and ((n(n - 1))/2)
• ((n(n - 1))/2) and 2n
• ((n(n - 1))/2) and n

Question 66

A Binary Search Tree (BST) stores values in the range 37 to 573. Consider the following sequence of keys.

I.  81, 537, 102, 439, 285, 376, 305

II. 52, 97, 121, 195, 242, 381, 472

III. 142, 248, 520, 386, 345, 270, 307

IV. 550, 149, 507, 395, 463, 402, 270 

Suppose the BST has been unsuccessfully searched for key 273. Which all of the above sequences list nodes in the order in which we could have encountered them in the search?

• II and III only
• I and III only
• III and IV only
• III only

Question 67

A Binary Search Tree (BST) stores values in the range 37 to 573. Consider the following sequence of keys.
I. 81, 537, 102, 439, 285, 376, 305
II. 52, 97, 121, 195, 242, 381, 472
III. 142, 248, 520, 386, 345, 270, 307
IV. 550, 149, 507, 395, 463, 402, 270
Which of the following statements is TRUE?

• I, II and IV are inorder sequences of three different BSTs
• I is a preorder sequence of some BST with 439 as the root
• II is an inorder sequence of some BST where 121 is the root and 52 is a leaf
• IV is a postorder sequence of some BST with 149 as the root

Question 68

How many distinct BSTs can be constructed with 3 distinct keys?

• 4
• 5
• 6
• 9

Question 69

Student (school-id, sch-roll-no, sname, saddress)
School (school-id, sch-name, sch-address, sch-phone)
Enrolment(school-id sch-roll-no, erollno, examname)
ExamResult(erollno, examname, marks)
What does the following SQL query output?

C

SELECT	sch-name, COUNT (*)
FROM	School C, Enrolment E, ExamResult R
WHERE	E.school-id = C.school-id
AND
E.examname = R.examname AND E.erollno = R.erollno
AND
R.marks = 100 AND S.school-id IN (SELECT school-id
                                FROM student
                                GROUP BY school-id
                                 HAVING COUNT (*) > 200)
GROUP By school-id
 /* Add code here. Remove these lines if not writing code */ 

• for each school with more than 200 students appearing in exams, the name of the school and the number of 100s scored by its students
• for each school with more than 200 students in it, the name of the school and the number of 100s scored by its students
• for each school with more than 200 students in it, the name of the school and the number of its students scoring 100 in at least one exam
• nothing; the query has a syntax error

Question 70

A binary tree with n > 1 nodes has n₁, n₂ and n₃ nodes of degree one, two and three respectively. The degree of a node is defined as the number of its neighbors.
n₃ can be expressed as

• n₁ + n₂ - 1
• n₁ - 2
• [((n₁ + n₂)/2)]
• n₂ - 1