UGCNET Computer Science August 2016 Paper II Retest

Q1. The Boolean function [~ (~p˄q)˄~(~p˄~q)]˅(p˄r) is equal to the Boolean function:

(A) q

(B) p˄r

(D) p

Ans .

(D) p

Explanation :

Q2. Let us assume that you construct ordered tree to represent the compound proposition (~(p˄q))↔(~p˅~q). Then, the prefix expression and post-fix expression determined using this ordered tree are given as ........... and ............. respectively.

(A) ↔~˄pq˅ ~~pq, pq˄~p~q~˅↔

(B) ↔~˄pq˅ ~p~q, pq˄~p~q~˅↔

(D) ↔~˄pq˅ ~p~q, pq˄~p~~q˅↔

Ans .

(B) ↔~˄pq˅ ~p~q, pq˄~p~q~˅↔

Explanation :
(~(p˄q))↔(~p˅~q)

Q3. Let A and B be sets in a finite universal set U. Given the following:
|A – B|, |AB|, |A|+|B| and |AB|
which of the following is in order of increasing size ?

(A) |A – B| ≤ |AB| ≤ |A| + |B| ≤ |AB|

(B) |AB| ≤ |A – B| ≤ |AB| ≤ |A| + |B|

(D) |A – B| ≤ |AB| ≤ |AB| ≤ |A| + |B|

Ans .

(D) |A – B| ≤ |AB| ≤ |AB| ≤ |A| + |B|

Explanation :

Q4. What is the probability that a randomly selected bit string of length 10 is a palindrome?

(A) 1/64

(B) 1/32

(D) 1/4

Ans .

(B) 1/32

Explanation :
select 10 bits and with every bit we have two choice either 0 or 1 so the total no of 10 length bit strings are 2^10
Now in palindrome if we chose first 5 bits then our job is done as next 5 are fixed ( first 5 in reverse order).
So, for five bits can be chosen in 25 (for every bit either 0 or 1).
Probability = 2^5/2^10= 1/ 32

Q5. Given the following graphs : Which of the following is correct?

(A) G1 contains Euler circuit and G2 does not contain Euler circuit.

(B) G1 does not contain Euler circuit and G2 contains Euler circuit. (

C) Both G1 and G2 do not contain Euler circuit.

(D) Both G1 and G2 contain Euler circuit.

Ans .

C) Both G1 and G2 do not contain Euler circuit.

Explanation :

Q6. The octal number 326.4 is equivalent to

(A) (214.2)10 and (D6.8)16

(B) (212.5)10 and (D6.8)16

(D) (214.5)10 and (D6.4)16

Ans .

Explanation :

Q7. Which of the following is the most efficient to perform arithmetic operations on the numbers?

(A) Sign-magnitude

(B) 1’s complement

(D) 9’s complement

Ans .

Explanation :

Q8. The Karnaugh map for a Boolean function is given as The simplified Boolean equation for the above Karnaugh Map is

(A) AB + CD + AB’ + AD

(B) AB + AC + AD + BCD

(D) AB + AC + BC + BCD

Ans .

(B) AB + AC + AD + BCD

Explanation :

Q9. Which of the following logic operations is performed by the following given combinational circuit ?

(A) EXCLUSIVE-OR

(B) EXCLUSIVE-NOR

(D)NOR

Ans .

(A) EXCLUSIVE-OR

Explanation :
(X+(X+Y)’)’ + (Y+(X+Y)’)’
Apply DE MORGAN theorem
X'(X+Y)+Y'(X+Y)
XX’+X’Y+Y’X+Y’Y
0+X’Y+Y’X+0
X XOR Y

Q10. Match the following:

(A) iii ii iv i

(B) ii iv i iii

(D) iii i iv ii

Ans .

(D) iii i iv ii

Explanation :
Half adder-> Its is used to add 2 bits.
Full adder-> It is used to add 3 bits.
controlled inverter-> a circuit that transmits a binary word or its 1’s complement
Binary adder -> It is used to add 2 binary numbers

Q11. Given i= 0, j = 1, k = – 1 x = 0.5, y = 0.0 What is the output of given ‘C’ expression ? x * 3 & & 3 || j | k

(A) -1

(B) 0

(D) 2

Ans .

(D) 2

Explanation :
⇒⇒ (x*3)&&3 || j | k
⇒⇒ 0&&3 || (j | k)
⇒⇒ 0&&3 || 1
⇒⇒ (0&&3) || 1
⇒⇒ 0||1
⇒⇒ 1

Q12. The following ‘C’ statement :
int * f[ ]( );
declares :

(A) A function returning a pointer to an array of integers.

(B) Array of functions returning pointers to integers.

(D) An illegal statement.

Ans .

(B) Array of functions returning pointers to integers.

Explanation :
f is an array of integer pointers and return type of a function
int * f[] () as we can see that return type of function is an array of pointers i.e. f

Q13. If a function is friend of a class, which one of the following is wrong ?

(A) A function can only be declared a friend by a class itself.

(B) Friend functions are not members of a class, they are associated with it.

(D) It can have access to all members of the class, even private ones.

Ans .

Explanation :
friend function is not a member of class it works as a bridge between Two classes.

Q14. In C++, polymorphism requires:

(A) Inheritance only

(B) Virtual functions only

(D) Inheritance, Virtual functions and references

Ans .

(D) Inheritance, Virtual functions and references

Explanation :
Polymorphism requires inheritance, Virtual functions and references

Q15. A function template in C++ provides ............ level of generalization.

(A) 4

(B) 3

(D) 1

Ans .

Explanation :

Q16. DBMS provides the facility of accessing data from a database through

(A) DDL

(B) DML

(D) Schema

Ans .

(B) DML

Explanation :

Q17. Relational database schema normalization is NOT for:

(A) reducing the number of joins required to satisfy a query.

(B) eliminating uncontrolled redundancy of data stored in the database.

(D) ensuring that functional dependencies are enforced.

Ans .

(A) reducing the number of joins required to satisfy a query.

Explanation :

Q18. Consider the following statements regarding relational database model:
(a) NULL values can be used to opt a tuple out of enforcement of a foreign key.
(b) Suppose that table T has only one candidate key. If Q is in 3NF, then it is also in BCNF.
(c) The difference between the project operator (P) in relational algebra and the SELECT keyword in SQL is that if the resulting table/set has more than one occurrences of the same tuple, then P will return only one of them, while SQL SELECT will return all. One can determine that:

(A) (a) and (b) are true.

(B) (a) and (c) are true.

(D) (a), (b) and (c) are true.

Ans .

(D) (a), (b) and (c) are true.

Explanation :

Q19. Consider the following Entity-Relationship (E-R) diagram and three possible relationship sets (I, II and III) for this E-R diagram: If different symbols stand for different values (e.g., t1 is definitely not equal to t2), then which of the above could not be the relationship set for the E-R diagram ?

(A) I only

(B) I and II only

(D) I, II and III

Ans .

(A) I only

Explanation :
We know that cardinalty constraints on more-than-binary relationship with more than one arrow (1 sides) creates ambiguity in ER diagram. [For more info on this, please refer to the DBMS book by Korth]
The given ER diagram can mean any one of the following two cases:
Case 1: PQ → ST
Case 2: PQS → T and PQT → S
Now, going through the three instances, we can identify the FDs and non-FDs satisfied for the instances as follows:
Instance 1:
PQ↛ T (so, case 1 isnot valid)
PQS ↛ T (so, case 2 is also not vaid)
So, the ER-diagram can NOT be a representation of Instance 1.
Instance 2:
PQ↛ S and PQ↛ T (so, case 1 is not valid)
However, PQS → T and PQT → S (so, case 2 is valid)
So, the ER-diagram can be a representation of Instance 2.
Instance 3:
PQ → S and PQ → T as well (so, case 1 is valid)
Validy of case 1 ensures validity of the FDs in case 2 as well.
So, the ER-diagram can also be a representation of Instance 3.
Therefore, correct answer is (A) I only.

Q20. Consider a database table R with attributes A and B. Which of the following SQL queries is illegal ?

(A) SELECT A FROM R;

(B) SELECT A, COUNT(*) FROM R;

(D) SELECT A, B, COUNT(*) FROM R GROUP BY A, B;

Ans .

(B) SELECT A, COUNT(*) FROM R;

Explanation :
Aggregate functions,grouping attribute must be used with group by clause.

Q21. Consider an implementation of unsorted single linked list. Suppose it has its representation with a head and a tail pointer (i.e. pointers to the first and last nodes of the linked list). Given the representation, which of the following operation cannot be implemented in O(1) time ?

(A) Insertion at the front of the linked list.

(B) Insertion at the end of the linked list.

(D) Deletion of the last node of the linked list.

Ans .

(D) Deletion of the last node of the linked list.

Explanation :
A)Insertion at the front of the linked list.
new_node->next=head;
head=new_node;
Θ(1)
B) Insertion at the end of the linked list.
Tail->next=new_node;
new_node->next=NULL;
Θ(1)
C) Deletion of the front node of the linked list.
Next_node=Head;
Head=Next_node->next;
free(Next_node);
Θ(1)
D)Deletion of the last node of linked list
Here, we have tail pointer but it will be of no use because there is no previous pointer (as it is single linked list).we need to have second last pointer so that we make it the last pointer and can free the last pointer i.e deleting the last node.So we need to traverse the whole linked list making it Θ(n).
struct node *p,*prev;
p=head;
while(p)
{
prev=p;
p=p->next;
}
prev->next=NULL;
free(p);
so ANSWER is (d)

Q22. Consider an undirected graph G where self-loops are not allowed. The vertex set of G is {(i, j) | 1 ≤ i ≤ 12, 1 ≤ j ≤ 12}. There is an edge between (a, b) and (c, d) if |a – c| ≤ 1 or |b–d| ≤ 1. The number of edges in this graph is

(A) 726

(B) 796

(D) 616

Ans .

(D) 616

Explanation :

Q23. The runtime for traversing all the nodes of a binary search tree with n nodes and printing them in an order is

(A) O(lg n)

(B) O(n lg n)

(D) O(n2)

Ans .

Explanation :
Printing the elements in an order means the elements should be printed in sorted order and we know inorder traversal of BST takes gives the sorted order and takes O(n) time.The recurrence involved is :
T(n) = 2T(n/2) + c for balanced BST which on solving gives O(n).

Q24. Consider the following statements :
S1: A queue can be implemented using two stacks.
S2: A stack can be implemented using two queues.
Which of the following is correct ?

(A) S1 is correct and S2 is not correct.

(B) S1 is not correct and S2 is correct.

(D) Both S1 and S2 are not correct.

Ans .

Explanation :
Both of the statements are true.
A queue can be implemented using two stacks:
Consider two stacks s1 & s2 ( we will be using STL stacks for implementation ).
Enqueue Operation :: Simply push the element onto s1.
Dequeue Operation :: Transfer all elements from s1 onto s2. Popthe top element from s2. Transfer remaining elements from s2 back to s1.
A stack can be implemented using two queues: Let S1 and S2 be the two Stacks to be used in the implementation of queues.
struct Stack
{ struct Queue *Q1;
struct Queue *Q2;
}
We make sure that one queue is empty always.
Push operation : Whichever queue is not empty, insert the element in it.
Check whether queue Q1 is empty or not. If Q1 is empty then Enqueue the element in it.
Otherwise EnQueue the element into Q1.
Push (struct Stack *S, int data) { if(isEmptyQueue(S->Q1) EnQueue(S->Q2, data);

else EnQueue(S->Q1, data); }
Time Complexity: O(1)
Pop Operation: Transfer n-1 elements to other queue and delete last from queue for performing pop operation.
If queue Q1 is not empty then transfer n-1 elements from Q1 to Q2 and then, DeQueue the last element of Q1 and return it.
If queue Q2 is not empty then transfer n-1 elements from Q2 to Q1 and then, DeQueue the last element of Q2 and return it.

Q25. Given the following prefix expression:
* + 3 + 3 ↑ 3 + 3 3 3
What is the value of the prefix expression?

(A) 2178

(B) 2199

(D) 2232

Ans .

Explanation :
=> * + 3 + 3 ^ 3 ( 3+ 3) 3
=> * + 3 + 3 ^ 3 6 3
=> * + 3 + 3 (3^6) 3
=> * + 3 + 3 729 3
=> * + 3 ( 3 + 729 ) 3
=> * + 3 732 3
=> * ( 3 + 732) 3
=> * 735 3
=> (735 ) * 3
=> 2205 ( ans- C)

Q26. Which of the following statements is not true with respect to microwaves?

(A) Electromagnetic waves with frequencies from 300 GHz to 400 THz.

(B) Propagation is line-of-sight.

(D) Use of certain portions of the band requires permission from authorities.

Ans .

(A) Electromagnetic waves with frequencies from 300 GHz to 400 THz.

Explanation :
electromagnetic radiationwith wavelengths ranging from one meter to one millimeter; with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm)

Q27. In a fast Ethernet cabling, 100 Base-TX uses ........... cable and maximum segment size is ............

(A) twisted pair, 100 metres

(B) twisted pair, 200 metres

(D) fibre optics, 2000 metres

Ans .

(A) twisted pair, 100 metres

Explanation :
100 Base-TX uses 100 Base-TX uses cable and maximum segment size is 100 metres

Q28. A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute with each frame carrying an average of 10,000 bits. What is the throughput of this network ?

(A) 1 Mbps

(B) 2 Mbps

(D) 12 Mbps

Ans .

(B) 2 Mbps

Explanation :
12000*10000/60= 2 Mbps

Q29. Match the following:

(A) iv i ii iii

(B) i iv ii iii

(D) iv ii i iii

Ans .

(A) iv i ii iii

Explanation :
a) Application layer is the topmost layer in TCP/IP protocol stack.Hence is related to software related things.
b) Presentation layer presents the data in proper format for transmission so it is concerned with semantics of the data.
c) Session layer maintains multiple connections and synchronization since we know session is a combination of multiple connections and hence it is associated with dialog control management
d) transport layer deals with flow control and congestion control mainly.

Q30. Which of the following protocols is used by email server to maintain a central repository that can be accessed from any machine?

(A) POP3

(B) IMAP

(D) DMSP

Ans .

(B) IMAP

Explanation :

Q31. The number of strings of length 4 that are generated by the regular expression (0+1+|2+3+)*, where | is an alternation character and {+, *} are quantification characters, is:

(A) 08

(B) 09

(D) 12

Ans .

Explanation :

Q32. The content of the accumulator after the execution of the following 8085 assembly language program, is MVI A, 35H
MOV B, A
STC
CMC
RAR
XRA B

(A) 00H

(B) 35H

(D) 2FH

Ans .

(D) 2FH

Explanation :
MVI A, 35H // content of accumulator = 35H = 0011 0101
MOV B, A // content of register B = 35H
STC // set carry flag = 1.
CMC // complement carry flag = not( 1) = 0.
RAR // Each binary bit of the accumulator is rotated right by one position through the Carry flag. And modify carry = D0.
and D7 = previous carry. // Now content of accumulator = 0001 1010 , carry = 1.
XRA B // The content of accumulator are exclusive OR with register B.
(0011 0101 )XOR ( 0001 1010 )
= 0010 1111
= 2F H

Q33. In compiler optimization, operator strength reduction uses mathematical identities to replace slow math operations with faster operations. Which of the following code replacements is an illustration of operator strength reduction?

(A) Replace P + P by 2 * P or Replace 3 + 4 by 7.

(B) Replace P * 32 by P<<5

(D) Replace (P<<4) – P by P * 15

Ans .

(B) Replace P * 32 by P<<5

Explanation :

Q34. Which of the following are the principles tasks of the linker?
I. Resolve external references among separately compiled program units.
II. Translate assembly language to machine code.
III. Relocate code and data relative to the beginning of the program.
IV . Enforce access-control restrictions on system libraries.

(A) I and II

(B) I and III

(D) I and IV

Ans .

(B) I and III

Explanation :
Linker Tasks: I and III
Assembler task: II
Access control task: IV

Q35. Which of the following is FALSE?

(A) The grammar S→aS|aSbS|, where S is the only non-terminal symbol, and is the null string, is ambiguous.

(B) An unambiguous grammar has same left most and right most derivation.

(D) Recursive descent parser is a top-down parser.

Ans .

(B) An unambiguous grammar has same left most and right most derivation.

Explanation :

Q36. Consider a system with seven processes A through G and six resources R through W .
Resource ownership is as follows:
process A holds R and wants T
process B holds nothing but wants T
process C holds nothing but wants S
process D holds U and wants S & T
process E holds T and wants V
process F holds W and wants S
process G holds V and wants U
Is the system deadlocked ? If yes, ............. processes are deadlocked.

(A) No

(B) Yes, A, B, C

(D) Yes, A, B, F

Ans .

Explanation :

Q37. Suppose that the virtual Address space has eight pages and physical memory with four page frames. If LRU page replacement algorithm is used, .............. number of page faults occur with the reference string.
0 2 1 3 5 4 6 3 7 4 7 3 3 5 5 3 1 1 1 7 2 3 4 1

(A) 11

(B) 12

(D) 9

Ans .

(A) 11

Explanation :

Q38. Consider a system having ‘m’ resources of the same type. These resources are shared by three processes P1, P2 and P3 which have peak demands of 2, 5 and 7 resources respectively. For what value of ‘m’ deadlock will not occur?

(A) 70

(B) 14

(D) 7

Ans .

(B) 14

Explanation :
Peak demands of p1,p2,p3 are 2,5 and 7.
allocate 1 less than peak demand i.e,, p1 –> 1 ,p2–>4 ,p3–>6
the number of resources for which deadlock occurs is 1+4+6 = 11
Add one to the number of resources we get 12 ,the value for which deadlock will not occur . ( 13 is nearest possible answer )

Q39. Five jobs A, B, C, D and E are waiting in Ready Queue. Their expected runtimes are 9, 6, 3, 5 and x respectively. All jobs entered in Ready queue at time zero. They must run in ............. order to minimize average response time if 3 < x < 5.

(A) B, A, D, E, C

(B) C, E, D, B, A

(D) C, B, A, E, D

Ans .

(B) C, E, D, B, A

Explanation :

Q40. Consider three CPU intensive processes P1, P2, P3 which require 20, 10 and 30 units of time, arrive at times 1, 3 and 7 respectively. Suppose operating system is implementing Shortest Remaining Time first (preemptive scheduling) algorithm, then .............. context switches are required (suppose context switch at the beginning of Ready queue and at the end of Ready queue are not counted).

(A) 3

(B) 2

(D) 5

Ans .

(A) 3

Explanation :

Q41. Which of the following is used to determine the specificity of requirements ?
Where n1 is the number of requirements for which all reviewers have identical interpretations, n2 is number of requirements in a specification.

(A) n1/n2

(B) n2/n1

(D) n1–n2

Ans .

(A) n1/n2

Explanation :

Q42. The major shortcoming of waterfall model is

(A) the difficulty in accommodating changes after requirement analysis.

(B) the difficult in accommodating changes after feasibility analysis.

(D) the maintenance of system.

Ans .

(A) the difficulty in accommodating changes after requirement analysis.

Explanation :

Q43. The quick design of a software that is visible to end users leads to ............

(A) iterative model

(B) prototype model

(D) waterfall model

Ans .

(B) prototype model

Explanation :
Prototype model: The basic idea here is that instead of freezing the requirements before a design or coding can proceed, a throwaway prototype is built to understand the requirements. This prototype is developed based on the currently known requirements. By using this prototype, the client can get an “actual feel” of the system, since the interactions with prototype can enable the client to better understand the requirements of the desired system. Prototyping is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determining the requirements. Waterfall model is the simplest model of software development paradigm. It says the all the phases of SDLC will function one after another in linear manner. Iterative model leads the software development process in iterations. It projects the process of development in cyclic manner repeating every step after every cycle of SDLC process. V -model‘ is also used by many of the companies in their product. ‘V -model’ is nothing but ‘Verification’ and ‘Validation’ model. In ‘V -model’ the developer’s life cycle and tester’s life cycle are mapped to each other. In this model testing is done side by side of the development. Likewise ‘Incremental model’, ‘RAD model’, ‘Iterative model’ and ‘Spiral model’ are also used based on the requirement of the customer and need of the product. Big Bang Model This model is the simplest model in its form. It requires little planning, lots of programming and lots of funds. This model is conceptualized around the big bang of universe.

Q44. For a program of k variables, boundary value analysis yields .............. test cases.

(A) 4k – 1

(B) 4k

(D) 2k – 1

Ans .

Explanation :
boundary value analysis 4n+1
Robusness testing 6n+1
worst case testing 5n

Q45. The extent to which a software performs its intended functions without failures, is termed as

(A) Robustness

(B) Correctness

(D) Accuracy

Ans .

Explanation :
Reliability is the probability of failure-free operation of a system over a specified time within a specified environment for a specified purpose Robustness is the ability of a computer system to cope with errors during execution and cope with erroneous input. Correctness of an algorithm is asserted when it is said that the algorithm is correct with respect to a specification Accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity’s true value

Q46. An attacker sits between the sender and receiver and captures the information and retransmits to the receiver after some time without altering the information. This attack is called as ..............

(A) Denial of service attack

(B) Masquarade attack

(D) Complex attack

Ans .

(A) Denial of service attack

Explanation :
Simple And Complex Attack-:Heard first time of this type of attack,classification is actually active and passive attack.
Denial of service attack-:Not Giving/allowing Legitimate user to access /use his resources which he is supposed to use.
Masquarade attack-:Using fake identity to gain unauthorized access. Given Question is a type of Man in the middle attack.

Q47. ................. is subject oriented, integrated, time variant, nonvolatile collection of data in support of management decisions.

(A) Data mining

(B) Web mining

(D) Database Management System

Ans .

Explanation :
DATA WAREHOUSE is subject oriented, integrated, time variant, non-volatile collection of data in support of management decisions.a large store of data accumulated from a wide range of sources within a company and used to guide management decisions.

Q48. In Data mining, classification rules are extracted from ..............

(A) Data

(B) Information

(D) Database

Ans .

Explanation :
A decision tree is a graph that uses a branching method to illustrate every possible outcome of a decision. Decision trees can be drawn by hand or created with a graphics program or specialized software. Informally, decision trees are useful for focusing discussion when a group must make a decision and classification rules are extracted from Decision tree

Q49. Discovery of cross sales opportunities is called as ...............

(A) Association

(B) Visualization

(D) Segmentation

Ans .

(A) Association

Explanation :
Cross-selling is the action or practice of selling an additional product or service to an existing customer. In practice, businesses define cross-selling in many different ways. Elements that might influence the definition might include the size of the business, the industry sector it operates within and the financial motivations of those required to define the term.
The objectives of cross-selling can be either to increase the income derived from the client or to protect the relationship with the client or clients. The approach to the process of cross-selling can be varied.

Q50. In Data mining, .............. is a method of incremental conceptual clustering.

(A) STRING

(B) COBWEB

(D) OLAD

Ans .

(B) COBWEB

Explanation :

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