UGCNET Computer Science June 2015 Paper II

Q1. How many strings of 5 digits have the property that the sum of their digits is 7 ?

(A) 66

(B) 330

(D) 99

Ans .

(B) 330

Explanation :
Let n=7 and r=5.
n+r-1Cr-1=330

Q2. Consider an experiment of tossing two fair dice, one black and one red. What is the probability that the number on the black die divides the number on red die ?

(A) 22 / 36

(B) 12 / 36

(D) 6 / 36

Ans .

Explanation :

Q3. In how many ways can 15 indistinguishable fish be placed into 5 different ponds, so that each pond contains at least one fish ?

(A) 1001

(B) 3876

(D) 200

Ans .

(A) 1001

Explanation :
15C1x14C4/15

Q4. Consider the following statements:
(a) Depth - first search is used to traverse a rooted tree.
(b) Pre - order, Post-order and Inorder are used to list the vertices of an ordered rooted tree.
(c) Huffman's algorithm is used to find an optimal binary tree with given weights.
(d) Topological sorting provides a labelling such that the parents have larger labels than their children.
Which of the above statements are true ?

(A) (a) and (b)

(B) (c) and (d)

(D) (a), (b) , (c) and (d)

Ans .

(D) (a), (b) , (c) and (d)

Explanation :

Q5. Consider a Hamiltonian Graph (G) with no loops and parallel edges. Which of the following is true with respect to this Graph (G) ?
(a) deg(v) ≥ n/2 for each vertex of G
(b) |E(G)| ≥ 1/2 (n-1)(n-2)+2 edges
(c) deg(v) + deg(w) ≥ n for every v and w not connected by an edge

(A) (a) and (b)

(B) (b) and (c)

(D) (a), (b) and (c)

Ans .

(D) (a), (b) and (c)

Explanation :

Q6. Consider the following statements :
(a) Boolean expressions and logic networks correspond to labelled acyclic digraphs.
(b) Optimal Boolean expressions may not correspond to simplest networks.
(c) Choosing essential blocks first in a Karnaugh map and then greedily choosing the largest remaining blocks to cover may not give an optimal expression.
Which of these statement(s) is/ are correct?

(A) (a) only

(B) (b) only

(D) (a), (b) and (c)

Ans .

(D) (a), (b) and (c)

Explanation :

Q7. Consider a full-adder with the following input values:
(a) x=1, y=0 and Ci(carry input) = 0
(b) x=0, y=1 and Ci = 1,br> Compute the values of S(sum) and C0 (carry output) for the above input values.

(A) S=1 , C0= 0 and S=0 , C0= 1

(B) S=0 , C0= 0 and S=1 , C0= 1

(D) S=0 , C0= 1 and S=1 , C0= 0

Ans .

(A) S=1 , C0= 0 and S=0 , C0= 1

Explanation :

Q8. "lf my computations are correct and I pay the electric bill, then I will run out of money. If I don't pay the electric bill, the power will be turned off. Therefore, if I don't run out of money and the power is still on, then my computations are incorrect."
Convert this argument into logical notations using the variables c, b, r , p for propositions of computations, electric bills, out of money and the power respectively. (Where ¬ means NOT)

(A) if (c ∧ b) → r and ¬b → ¬p, then (¬r ∧ p)→¬c

(B) if (c ∨ b) → r and ¬b → ¬p, then (r ∧ p)→c

(D) if (c ∨ b) → r and ¬b → ¬p, then (¬r ∧ p)→¬c

Ans .

(A) if (c ∧ b) → r and ¬b → ¬p, then (¬r ∧ p)→¬c

Explanation :

Q9. Match the following:

(A) (i) (ii) (iii) (iv)

(B) (ii) (iii) (i) (iv)

(D) (iv) (ii) (iii) (i)

Ans .

(A) (i) (ii) (iii) (iv)

Explanation :

Q10. Consider a proposition given as:
"x≥6, if x2≥25 and its proof as:
If x≥6, then x2=x.x=6.6=36≥25
Which of the following is correct w.r .to the given proposition and its proof ?
(a) The proof shows the converse of what is to be proved.
(b) The proof starts by assuming what is to be shown.
(c) The proof is correct and there is nothing wrong.

(A) (a) only

(B) (c) only

(D) (b) only

Ans .

Explanation :
Proof says any number greater than or equal to 6, its square is greater than or equal to 25.
6×6>25. 7×7>25——-.
Proposition 1 Fails because it does not prove that number (6,7,8—) square is not greater than 25.
Proposition 2 fails because there is no requirement of assumption as numbers are already given.
Proposition 3 is correct.

Q11. What is the output of the following program ?
(Assume that the appropriate pre-processor directives are included and there is no syntax error)
main()
{
char S[ ] = "ABCDEFGH";
printf ("%C",* (& S[3]));
printf ("%s", S+4);
printf ("%u", S);
/* Base address of S is 1000 */
}

(A) ABCDEFGH1000

(B) CDEFGH1000

(D) DEFGH1000

Ans .

(D) DEFGH1000

Explanation :
S[0]=A at address 1000.
S[1]=B at address 1001.
S[2]=C at address 1002.
S[3]=D. at address 1003.
S[4]=E. at address 1004.
S[5]=F S[6]=G S[7]=H.
printf(“%c”,*(&S[3]));
prints character at subscript S[3].
printf(“%s”,S+4);
prints from base address 1000+4.
printf(“%u”,S);
prints base address.

Q12. Which of the following, in C++, is inherited in a derived class from base class ?

(A) constructor

(B) destructor

(D) virtual methods

Ans .

Explanation :

Q13. Given that x=7.5, j=-1.0, n=1.0, m=2.0 the value of --x+j == x>n>=m is:

(A) 0

(B) 1

(D) 3

Ans .

(A) 0

Explanation :
–(x)+-1.0==7.5>1>=2.
5.5==7.5>0 (as 1>=2 is false).
6.5==1.(as 7.5>0).
6.5==1 is false.

Q14. Which of the following is incorrect in C++ ?

(A) When we write overloaded function we must code the function for each usage.

(B) When we write function template we code the function only once.

(D) Templates are more efficient than macros

Ans .

(D) Templates are more efficient than macros

Explanation :

Q15. When the inheritance is private, the private methods in base class are ____________ in the derived class (in C++).

(A) inaccessible

(B) accessible

(D) public

Ans .

(A) inaccessible

Explanation :

Q16. An Assertion is a predicate expressing a condition we wish database to always satisfy. The correct syntax for Assertion is :

(A) CREATE ASSERTION ‘ASSERTION Name’ CHECK ‘Predicate’

(B) CREATE ASSERTION ‘ASSERTION NAME’

(D) SELECT ASSERTION

Ans .

(A) CREATE ASSERTION ‘ASSERTION Name’ CHECK ‘Predicate’

Explanation :
1.An assertion is a predicate expressing a condition we wish the database to always satisfy.
2. Domain constraints, functional dependency and referential integrity are special forms of assertion.
3. Where a constraint cannot be expressed in these forms, we use an assertion.
e.g. Ensuring the sum of loan amounts for each branch is less than the sum of allaccount balances at the branch. Ensuring every loan customer keeps a minimum of $100 in an account.
4. An assertion in DQL-92 takes the form.

Q17. Which of the following concurrency protocol ensures both conflict serializability and freedom from deadlock ? (a) 2-phase Locking (b) Time stamp - ordering

(A) Both (a) and (b)

(B) (a) only

(D) Neither (a) nor (b)

Ans .

Explanation :

Q18. Drop Table cannot be used to drop a Table referenced by _______________ constraint. (a) Primary key (b) Sub key (c) Super key (d) Foreign key

(A) (a)

(B) (a), (b) and (c)

(D) (a) and (d)

Ans .

Explanation :

Q19. Database applications were built directly on top of file system to overcome the following drawbacks of using file-systems
(a) Data redundancy and inconsistency
(b) Difficulty in accessing Data
(c) Data isolation
(d) Integrity problems

(A) (a)

(B) (a) and (d)

(D) (a), (b), (c) and (d)

Ans .

(D) (a), (b), (c) and (d)

Explanation :

Q20. For a weak entity set to be meaningful, it must be associated with another entity set in combination with some of their attribute values, is called as :

(A) Neighbour Set

(B) Strong Entity Set

(D) Weak Set

Ans .

Explanation :

Q21. Consider the given graph: Its Minimum Cost Spanning Tree is _____________

(A)

(B)

(C)

(D)

Ans .

(B) smily face

Explanation :
Kruskal algo arrange weights in ascending order.
6-1->10
3-4->12
2-7->14
2-3->16
7-4->18
4-5->22
7-5->24
5-6->25
1-2->28.
put all the nodes in ascending order so that it does not form a circuit.untill all the nodes are traversed.
So nodes are.
6-1,3-4,2-7,2-3,4-5,5-6,1-2.
it avoids 7-4 and 7-5 to avoid the circuit.

Q22. The inorder and preorder Traversal of binary Tree are dbeafcg and abdecfg respectively. The post-order Traversal is _____________

(A) dbefacg

(B) debfagc

(D) debfgca

Ans .

(D) debfgca

Explanation :

Q23. Level order Traversal of a rooted Tree can be done by starting from root and performing:

(A) Breadth First Search

(B) Depth first search

(D) Deep search

Ans .

(A) Breadth First Search

Explanation :

Q24. The average case occurs in the Linear Search Algorithm when:

(A) The item to be searched is in some where middle of the Array

(B) The item to be searched is not in the array

(D) The item to be searched is either in the last or not in the array

Ans .

(A) The item to be searched is in some where middle of the Array

Explanation :
let there are n elements to be searched linearly.
1st element will take 1 search.
2nd element will take 2 search.
—-------
—-------
n th element will take n search.
Average search will take. (1+2+3—–n)/n
= n(n+1)/2n hence approximately n/2.
when item is not there it will search whole list.
last element will take n search time.
Hence option A is the correct

Q25. To determine the efficiency of an algorithm the time factor is measured by:

(A) Counting micro seconds

(B) Counting number of key operations

(D) Counting kilobytes of algorithm

Ans .

(B) Counting number of key operations

Explanation :

Q26. Which of the following protocols is an application layer protocol that establishes, manages and terminates multimedia sessions?

(A) Session Maintenance Protocol

(B) Real - time Streaming Protocol

(D) Session Initiation Protocol

Ans .

(D) Session Initiation Protocol

Explanation :

Q27. Match the following port numbers with their uses:

(A) (iv) (i) (ii) (iii)

(B) (ii) (i) (iv) (iii)

(D) (ii) (iv) (i) (iii)

Ans .

(D) (ii) (iv) (i) (iii)

Explanation :

Q28. Which of the following is not associated with the session layer ?

(A) Dialog control

(B) Token management

(D) Synchronization

Ans .

Explanation :

Q29. What is the size of the 'total length' field in IPv 4 datagram ?

(A) 4 bits

(B) 8 bits

(D) 32 bits

Ans .

Explanation :

Q30. Which of the following is/are restriction(s) in classless addressing ?

(A) The number of addresses needs to be a power of 2.

(B) The mask needs to be included in the address to define the block.

(D) All of the above

Ans .

(D) All of the above

Explanation :

Q31. Match the following:

(A) (ii) (iii) (iv) (i)

(B) (iii) (iv) (ii) (i)

(D) (iv) (iii) (ii) (i)

Ans .

(D) (iv) (iii) (ii) (i)

Explanation :

Q32. The translator which performs macro calls expansion is called :

(A) Macro processor

(B) Micro pre-processor

(D) Dynamic linker

Ans .

Explanation :

Q33. If all the production rules have single non - terminal symbol on the left side, the grammar defined is :

(A) context free grammar

(B) context sensitive grammar

(D) phrase grammar

Ans .

(A) context free grammar

Explanation :

Q34. Which one from the following is false ?

(A) LALR parser is Bottom - Up parser

(B) A parsing algorithm which performs a left to right scanning and a right most deviation is RL (1).

(D) In LL(1), the 1 indicates that there is a one - symbol look - ahead.

Ans .

(B) A parsing algorithm which performs a left to right scanning and a right most deviation is RL (1).

Explanation :

Q35. Which phase of compiler generates stream of atoms ?

(A) Syntax analysis

(B) Lexical Analysis

(D) Code optimization

Ans .

(A) Syntax analysis

Explanation :

Q36. A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cyclinders 12, 26, 24, 4, 42, 8 and 50 in that order . The driver is currently serving a request at cyclinder 24. A seek takes 6 msec per cyclinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?

(A) 0.984 sec

(B) 0.396 sec

(D) 0.42 sec

Ans .

(D) 0.42 sec

Explanation :
current position of head is at cylinder 24.
24->26->12->8->4->42->50.
total cylinders traversed are.
(2+14+4+4+38+8)=70 cylinders.
1 cylinders is traversed in 6 ms.
70 cylinders are traveresed in 420ms.= 420s/1000=0.42sec

Q37. Let Pi and Pj be two processes, R be the set of variables read from memory, and W be the set of variables written to memory. For the concurrent execution of two processes Pi and Pj, which of the following conditions is not true?

(A) R(Pi)∩W(Pj)=Φ

(B) W(Pi)∩R(Pj)=Φ

(D) W(Pi)∩W(Pj)=Φ

Ans .

Explanation :

Q38. A LRU page replacement is used with four page frames and eight pages. How many page faults will occur with the reference string 0172327103 if the four frames are initially empty?

(A) 6

(B) 7

(D) 8

Ans .

(B) 7

Explanation :
LRU
Whenever a page is used it is stamped with a counter value. When a page is to be replaced page with lowest stamp value is selected as the victim.
0172 3 2 7 1 0 3.
0(1 page fault,Counter=1),1(2 page fault,Counter=2),7(3 page fault,Counter=3),2 (4 page fault,Counter=4).
0 is selected as the victim .and replaced by.3. now frame is. 3(5 page fault,counter=5),1(2 page fault,Counter=2),7(3 page fault,Counter=3),2 (4 page fault,Counter=4)
2 is already in the frame so counter is increased. 3(5 page fault,counter=5),1(2 page fault,Counter=2),7(3 page fault,Counter=3),2 (4 page fault,Counter=6)
7 is already in the frame so counter is increased.3(5 page fault,counter=5),1(2 page fault,Counter=2),7(3 page fault,Counter=7),2 (4 page fault,Counter=6)
1 is already in the frame so counter is increased. 3(5 page fault,counter=5),1(2 page fault,Counter=8),7(3 page fault,Counter=7),2 (4 page fault,Counter=6)
0 is not in the frame so counter 5 is the least so 3 is replaced by 0.and page fault is increased.
0(6 page fault,counter=9),1(2 page fault,Counter=8),7(3 page fault,Counter=7),2 (4 page fault,Counter=6) 3 replaces 2
0(6 page fault,counter=9),1(2 page fault,Counter=8),7(3 page fault,Counter=7),3 (7 page fault,Counter=10)

Q39. What does the following command do? grep −vn “abc” x

(A) It will print all of the lines in the file x that match the search string “abc”

(B) It will print all of the lines in file x that do not match the search string “abc”

(D) It will print the specific line numbers of the file x in which there is a match for string “abc”

Ans .

(A) It will print all of the lines in the file x that match the search string “abc”

Explanation :

Q40. The Unix Kernel maintains two key data structures related to processes, the process table and the user structure. Which of following information is not the part of user structure?

(A) File descriptor table

(B) System call state

(D) Kernel stack

Ans .

Explanation :

Q41. Match the following:

(A) (iii) (iv) (i) (ii)

(B) (ii) (i) (iv) (iii)

(D) (iii) (i) (iv) (ii)

Ans .

(D) (iii) (i) (iv) (ii)

Explanation :

Q42. In which testing strategy requirements established during requirements analysis are validated against developed software?

(A) Validation testing

(B) Integration testing

(D) System testing

Ans .

(A) Validation testing

Explanation :

Q43. Which process model is also called as classic life cycle model?

(A) Waterfall model

(B) RAD model

(D) Incremental model

Ans .

(A) Waterfall model

Explanation :

Q44. Cohesion is an extension of:

(A) Abstraction concept

(B) Refinement concept

(D) Modularity

Ans .

Explanation :

Q45. Which one from the following is highly associated activity of project planning?

(A) Keep track of the project progress.

(B) Compare actual and planned progress and costs

(D) Both (B) and (C)

Ans .

Explanation :

Q46. In the case of parallelization, Amdahl's law states that if P is the proportion of a program that can be made parallel and (1-P) is the proportion that cannot be parallelized, then the maximum speed-up that can be achieved by using N processors is:

(A) 1/((1-P)+N.P)

(B) 1/((N-1)P+P)

(D) 1/(P+(1-P)/N)

Ans .

Explanation :

Q47. Which of the following statements is incorrect for Parallel Virtual Machine (PVM)?

(A) The PVM Communication model provides asynchronous blocking send, asynchronous blocking receive and non-blocking receive function.

(B) Message buffers are allocated dynamically.

(C) The PVM communication model assumes that any task can send a message to any other PVM task and that there is no limit to the size or number of such messages.

(D) In PVM Model, the message order is not preserved.

Ans .

(D) In PVM Model, the message order is not preserved.

Explanation :

Q48. Which of the following algorithms sort n integers, having the range 0 to (n2-1), in ascending order in O(n) time ?

(A) Selection sort

(B) Bubble sort

(D) Insertion sort

Ans .

Explanation :

Q49. Which of the following statements is FALSE about weak entity set ?

(A) Weak entities can be deleted automatically when their strong entity is deleted.

(B) Weak entity set avoids the data duplication and consequent possible inconsistencies caused by duplicating the key of the strong entity.

(D) Tuples in a weak entity set are not partitioned according to their relationship with tuples in a strong entity set.

Ans .

(D) Tuples in a weak entity set are not partitioned according to their relationship with tuples in a strong entity set.

Explanation :

Q50. Which of the following is not valid with reference to Message Passing Interface (MPI)?

(A) MPI can run on any hardware platform

(B) The programming model is a distributed memory model.

(D) MPI - Comm - Size returns the total number of MPI processes in specified communication.

Ans .

Explanation :

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