UGCNET Computer Science December 2015 Paper II

Q1. How many committees of five people can be chosen from 20 men and 12 women such that each committee contains at least three women?

(A) 75240

(B) 52492

(D) 9900

Ans .

(B) 52492

Explanation :
We must choose at least 3 women, so we calculate the case of 3 women, 4 women and 5 women and by addition rule add the results.
12C3 x 20C2 + 12C4 x 20C1 + 12C5 x 20C0 = (12x11x10/3x2x1) x (20x19/2x1) + (12x11x10x9/4x3x2x1) x 0 + (12x11x10x9x8/5x4x3x2x1) x 1 = 220 x 190 + 495 x 20 + 792 = 52492

Q2. Which of the following statement(s) is/are false?
(a) A connected multigraph has an Euler Circuit if and only if each of its vertices has even degree.
(b) A connected multigraph has an Euler Path but not an Euler Circuit if and only if it has exactly two vertices of odd degree.
(c) A complete graph (Kn) has a Hamilton Circuit whenever n≥3
(d) A cycle over six vertices (C6) is not a bipartite graph but a complete graph over 3 vertices is bipartite.

(A) (a) only

(B) (b) and (c)

(D) (d) only

Ans .

(D) (d) only

Explanation :
Euler Circuits
Hamilton Circuit
Bipartite Graph From the above definitions, we can see that (d) is false. So Answer is (D)

Q3. Which of the following is/are not true?
(a) The set of negative integers is countable.
(b) The set of integers that are multiples of 7 is countable.
(c) The set of even integers is countable.
(d) The set of real numbers between 0 and 1/2 is countable.

(A) (a) and (c)

(B) (b) and (d)

(D) (d) only

Ans .

(D) (d) only

Explanation :

Q4. Consider the graph given below: The two distinct sets of vertices, which make the graph bipartite are:

(A) (v1, v4, v6); (v2, v3, v5, v7, v8)

(B) (v1, v7, v8); (v2, v3, v5, v6)

(D) (v1, v4, v6, v7, v8); (v2, v3, v5)

Ans .

Explanation :
A simple graph G=(V ,E) is called bipartite if its vertex set can be partitioned into two disjoint subsets V=V1∪ V2, such that every edge has the form e=(a,b) where aϵV1 and bϵV2.
Bipartite graphs are equivalent to two-colorable graphs. 1. Assign Red color to the source vertex (putting into set V1).
2. Color all the neighbours with Black color (putting into set V2).
3. Color all neighbour’s neighbour with Red color (putting into set V1).
4. This way, assign color to all vertices such that it satisfies all the constraints of m way coloring problem where m = 2.
5. While assigning colors, if we find a neighbour which is colored with same color as current vertex, then the graph cannot be colored with 2 colors (ie., graph is not Bipartite).
So Answer is option (C).

Q5. A tree with n vertices is called graceful, if its vertices can be labelled with integers 1, 2, ...,n such that the absolute value of the difference of the labels of adjacent vertices are all different. Which of the following trees are graceful?

(A) (a) and (b)

(B) (b) and (c)

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

Ans .

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

Explanation :
Caterpillar tree: In graph theory, a caterpillar is a tree in which all the vertices are within distance 1 of a central path.
Theorem: All caterpillars are graceful.
So, (a), (b) and (c) are graceful.

Q6. Which of the following arguments are not valid?
(a) “If Gora gets the job and works hard, then he will be promoted. If Gora gets promotion, then he will be happy. He will not be happy, therefore, either he will not get the job or he will not work hard”.
(b) “Either Puneet is not guilty or Pankaj is telling the truth. Pankaj is not telling the truth, therefore, Puneet is not guilty”.
(c) If n is a real number such that n>1, then n2>1. Suppose that n2>1, then n>1.

(A) (a) and (c)

(B) (b) and (c)

(D) (a) and (b)

Ans .

(B) (b) and (c)

Explanation :
(a) P: Gora gets the job
Q: Gora works hard
R: Gora gets promotion
S: Gora will be happy
The argument can bet written as
(P˄Q)→R
R→S
¬S
Therefore ¬P˅¬Q
(b) Let P: Puneet is not guilty
Q: Pankaj is telling the truth
The argument can bet written as
P˅Q
~Q
Therefore, P
Thus by disjunctive syllogism, the argument is valid.

Disjunctive Syllogism:
The disjunctive syllogism rule may be written as:
P˅Q, ¬P ⊢ Q
It may also be written as:
((P˅Q)˄¬P)→Q
where P, and Q are propositions expressed in some formal system

Q7. Let P(m,n) be the statement “m divides n” where the Universe of discourse for both the variables is the set of positive integers. Determine the truth values of the following propositions.
(a) ∃ m∀ n P(m,n) (b) ∀ n P(1,n) (c) ∀ m ∀ n P(m,n)

(A) (a)-True; (b)-True; (c)-False

(B) (a)-True; (b)-False; (c)-False

(D) (a)-True; (b)-True; (c)-True

Ans .

(A) (a)-True; (b)-True; (c)-False

Explanation :

Q8. Match the following terms:

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

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

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

Ans .

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

Explanation :

Q9. Consider the compound propositions given below as: (a) p˅~(p˄q) (b) (p˄~q)˅~(p˄q) (c) p˄(q˅r) Which of the above propositions are tautologies?

(A) (a) and (c)

(B) (b) and (c)

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

Ans .

Not matched any option

Explanation :
because Only (a) p˅~(p˄q) is tautology.

Q10. Which of the following property/ies a Group G must hold, in order to be an Abelian group?
(a) The distributive property
(b) The commutative property
(c) The symmetric property

(A) (a) and (b)

(B) (b) and (c)

(D) (b) only

Ans .

(D) (b) only

Explanation :

Q11. Consider the following program:
#include
main() {
int i, inp;
float x,
term=1, sum=0;
scanf(“%d %f”,&inp, &x);
for(i=1;i<=inp;i++)
{
term=term*x/i;
sum=sum+term;
}
printf(“Result=%f\n”,sum); }
The program computes the sum of which of the following series?

(A) x+x2/2+x3/3+x4/4+...

(B) x+x2/2!+x3/3!+x4/4!+...

(D) 1+x2/2!+x3/3!+x4/4!+...

Ans .

(B) x+x2/2!+x3/3!+x4/4!+...

Explanation :
term =1 , sum=0
suppose inp entered = 3 so First iteration
term= 1*x/1 = x
sum = 0 + x =x

Second iteration
term = x*x/2= x2/2 =x2/2! sum= x+x2/2!

Third iteration
term = =x2/2! *x/3
=x3/3.2.1=x3/3! sum= x+x2/2!+x3/3!
and so on so sum= x+x2/2!+x3/3!+……

Q12. Consider the following two statements:
(a) A publicly derived class is a subtype of its base class.
(b) Inheritance provides for code reuse.
Which of the following statements is correct?

(A) Both the statements (a) and (b) are correct

(B) Neither of the statements (a) and (b) are correct

(D) Statement (a) is incorrect and (b) is correct

Ans .

(A) Both the statements (a) and (b) are correct

Explanation :
A publicly derived class is a subtype of its base class.
Inheritance provides for code reuse. BOTH are correct

Q13. Consider a “CUSTOMERS” database table having a column “CITY” filled with all the names of Indian cities (in capital letters). The SQL statement that finds all cities that have “GAR” somewhere in its name, is:

(A) Select *from customers where city=’%GAR%’;

(B) Select *from customers where city=’$GAR$’;

(D) Select *from customers where city as ’%GAR’;

Ans .

Explanation :
For Matching Any String in Oracle Like Operator is Used. also % symbol is used as a wild card character to represent multiple characters

Q14. Match the following database terms to their functions:

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

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

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

Ans .

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

Explanation :
Normalization: Reduces data redundancy in a database.
Data Dictionary: Contains metadata describing database structure.
Referential Integrity : Enforces match of primary key to foreign key.
External Schema: Define view(s) of the database for particular user(s).

Q15. In general, in a recursive and non-recursive implementation of a problem (program):

(A) Both time and space complexities are better in recursive than in non-recursive program

(B) Both time and space complexities are better in non-recursive than in recursive program

(C) Time complexity is better in recursive version but space complexity is better in non-recursive version of the program

(D) Space complexity is better in recursive version but time complexity is better in non-recursive version of the program

Ans .

(B) Both time and space complexities are better in non-recursive than in recursive program

Explanation :

Q16. A three dimensional array in ‘C’ is declared as int A[x][y][z]. Here, the address of an item at the location A[p][q][r] can be computed as follows (where w is the word length of an integer):

(A) &A[0][0][0]+w(y*z*q+z*p+r)

(B) &A[0][0][0]+w(y*z*p+z*q+r)

(D) &A[0][0][0]+w(x*y*q+z*p+r)

Ans .

(B) &A[0][0][0]+w(y*z*p+z*q+r)

Explanation :

Q17. In C++, which system-provided function is called when no handler is provided to deal with an exception?

(A) terminate()

(B) unexpected()

(D) kill()

Ans .

(A) terminate()

Explanation :
This function is provided so that the terminate handler can be explicitly called by a program that needs to abnormally terminate, and works even if set_terminate has not been used to set a custom terminate handler

Q18. Which of the following provides the best description of an entity type?

(A) A specific concrete object with a defined set of processes (e.g. Jatin with diabetes)

(B) A value given to a particular attribute (e.g. height-230 cm)

(D) A template for a group of things with the same set of characteristics that may exist in the real world

Ans .

(D) A template for a group of things with the same set of characteristics that may exist in the real world

Explanation :

Q19. Data which improves the performance and accessibility of the database are called:

(A) Indexes

(B) User Data

(D) Data Dictionary

Ans .

(A) Indexes

Explanation :

Q20. A relation R={A,B,C,D,E,F ,G} is given with following set of functional dependencies:
F={AD→E, BE→F , B→C, AF→G}
Which of the following is a candidate key?

(A) A

(B) AB

(D) ABD

Ans .

(D) ABD

Explanation :
ABD CLOSURE = { ABDE}={ABDEF}={ABCDEFG}
SO CANDIDATE KEY IS ABD

Q21. Which of the following services is not provided by wireless access point in 802.11 WLAN?

(A) Association

(B) Disassociation

(D) Integration

Ans .

Explanation :
IEEE 802.11 Services

Q22. Which of the following fields in IPv4 datagram is not related to fragmentation?

(A) Type of service

(B) Fragment offset

(D) Identification

Ans .

(A) Type of service

Explanation :

Q23. Four channels are multiplexed using TDM. If each channel sends 100 bytes/second and we multiplex 1 byte per channel, then the bit rate for the link is ______________

(A) 400 bps

(B) 800 bps

(D) 3200 bps

Ans .

(D) 3200 bps

Explanation :

Q24. In a typical mobile phone system with hexagonal cells, it is forbidden to reuse a frequency band in adjacent cells. If 840 frequencies are available, how many can be used in a given cell?

(A) 280

(B) 210

(D) 120

Ans .

(A) 280

Explanation :

Q25. Using p=3, q=13, d=7 and e=3 in the RSA algorithm, what is the value of ciphertext for a plain text 5?

(A) 13

(B) 21

(D) 33

Ans .

Marks to all

Explanation :
p=3, q=13, d=7, e=3, M=5, C=?
C = Me mod n
n = p*q
= 3*13 = 39
C = 53 mod 39
= 8 Answer is 8.

Q26. A virtual memory has a page size of 1K words. There are eight pages and four blocks. The associative memory page table contains the following entries:
Which of the following list of virtual addresses (in decimal) will not cause any page fault if referenced by the CPU?

(A) 1024, 3072, 4096, 6144

(B) 1234, 4012, 5000, 6200

(D) 2021, 4050, 5112, 7100

Ans .

Explanation :

Q27. Suppose that the number of instructions executed between page faults is directly proportional to the number of page frames allocated to a program. If the available memory is doubled, the mean interval between page faults is also doubled. Further , consider that a normal instruction takes one micro second, but if a page fault occurs, it takes 2001 micro seconds. If a program takes 60 sec to run, during which time it gets 15000 page faults, how long would it take to run if twice as much memory were available?

(A) 60 sec

(B) 30 sec

(D) 10 sec

Ans .

Explanation :

Q28. Consider a disk with 16384 bytes per track having a rotation time of 16 msec and average seek time of 40 msec. What is the time in msec to read a block of 1024 bytes from this disk?

(A) 57 msec

(B) 49 msec

(D) 17 msec

Ans .

(B) 49 msec

Explanation :
Time in msec to read a block of 1024 bytes (Access time or Disk Latency) = seek time + average rotational delay + transfer time
If there are 16384 bytes per track there are 1024/16384 tracks to be read for this block.
Seek time = 40 msec
Rotational delay = 16 msec
Transfer time = (sectors_read/sectors per rev.) x rotational delay
= (1024/16384) x 16 = 1
average rotational delay = rotational delay/2 = 16/2 = 8
access time = 40 + 8 + 1 = 49

Q29. A system has four processes and five allocatable resources. The current allocation and maximum needs are as follows: The smallest value of x for which the above system in safe state is ____________

(A) 1

(B) 3

(D) 0

Ans .

Marks to all

Explanation :

Q30. In Unix, the login prompt can be changed by changing the contents of the file ______________

(A) contrab

(B) init

(D) inittab

Ans .

Explanation :

Q31. A data cube C, has n dimensions, and each dimension has exactly p distinct values in the base cuboid. Assume that there are no concept hierarchies associated with the dimensions. What is the maximum number of cells possible in the data cube, C?

(A) pn

(B) p

(D) (p+1)n

Ans .

(D) (p+1)n

Explanation :
(a) What is the maximum number of cells possible in the base cuboid? pn. This is the maximum number of distinct tuples that you can form with p distinct values per dimensions.
(b) What is the minimum number of cells possible in the base cuboid? p. You need at least p tuples to contain p distinct values per dimension. In this case no tuple shares any value on any dimension.
(c) What is the minimum number of cells possible in the data cube, C? (2n-1)×p+1. The minimum number of cells is when each cuboid contains only p cells, except for the apex, which contains a single cell.
(d) What is the maximum number of cells possible (including both base cells and aggregate cells) in the data cube, C? (p+1)n.
The argument is similar to that of part (a), but now we have p+1 because in addition to the p distinct values of each dimension we can also choose ∗ .

Q32. Suppose that from given statistics, it is known that meningitis causes stiff neck 50% of the time, that the proportion of persons having meningitis is 1/50000, and that the proportion of people having stiff neck is 1/20. Then the percentage of people who had meningitis and complain about stiff neck is:

(A) 0.01%

(B) 0.02%

(D) 0.05%

Ans .

(B) 0.02%

Explanation :
The computation is based on the simplified Bayes’ formula.
P{B|A} = (P{A|B}·P{B) / P{A}.
P{M|S} = probability that a person had meningitis, conditioned by the existence of stiff neck.
P{S|M} = probability that a person complains about stiff neck, conditioned by the existence of meningitis. = 50%=1/2
P{S} = proportion of people who complain about stiff neck. = 1/20
P{M} = proportion of people who had meningitis. = 1/50,000
Then:
P{M|S} = (P{S|M}·P{M}) / P{S} =(1/2 x 1/50,000) / 1/20 = 0.0002 = 0.02%

Q33. _________________ system is market oriented and is used for data analysis by knowledge workers including Managers, Executives and Analysts.

(A) OLTP

(B) OLAP

(D) Market System

Ans .

(B) OLAP

Explanation :
– OLTP (On-line Transaction Processing) is characterized by a large number of short on-line transactions (INSERT, UPDATE, DELETE). The main emphasis for OLTP systems is put on very fast query processing, maintaining data integrity in multiaccess environments and an effectiveness measured by number of transactions per second. In OLTP database there is detailed and current data, and schema used to store transactional databases is the entity model (usually 3NF). – OLAP (On-line Analytical Processing) is characterized by relatively low volume of transactions. Queries are often very complex and involve aggregations. For OLAP systems a response time is an effectiveness measure. OLAP applications are widely used by Data Mining techniques. In OLAP database there is aggregated, historical data, stored in multi-dimensional schemas (usually star schema).

Q34. _______________ allows selection of the relevant information necessary for the data warehouse.

(A) The Top-Down View

(B) Data Warehouse Viewspan class="glyphicon glyphicon-remove">

(D) Business Query View

Ans .

(A) The Top-Down View

Explanation :

Q35. The hash function used in double hashing is of the form:

(A) h(k, i)=(h1(k)+h2(k)+i)mod m

(B) h(k, i)= (h1(k)+h2(k)-i)mod m

(D) h(k, i)=(h1(k)ih2(k))mod m

Ans .

Explanation :
Double hashing uses the idea of applying a second hash function to the key when a collision occurs. The result of the second hash function will be the number of positions form the point of collision to insert. There are a couple of requirements for the second function: it must never evaluate to 0 must make sure that all cells can be probed

Q36. In the following graph, discovery time stamps and finishing time stamps of Depth First Search (DFS) are shown as x/y where x is discovery time stamp and y is finishing time stamp. It shows which of the following depth first forest?

(A) {a,b,e} {c,d,f,g,h}

(B) {a,b,e} {c,d,h} {f,g}

(D) {a,b,c,d} {e,f,g} {h}

Ans .

(A) {a,b,e} {c,d,f,g,h}

Explanation :
Check for the Cycles in the graph, you will find that node A,B,E form one cycle. node F,G form another cycle. Node C,D form another cycle. and H is having self loop.

Q37. The number of disk pages access in B-tree search, where h is height, n is the number of keys, and t is the minimum degree, is:

(A) θ(logn h*t)

(B) θ(logt n*h)

(D) θ(logt n)

Ans .

(D) θ(logt n)

Explanation :

Q38. The inorder traversal of the following tree is:

(A) 2 3 4 6 7 13 15 17 18 18 20

(B) 20 18 18 17 15 13 7 6 4 3 2

(D) 2 4 3 13 7 6 15 17 20 18 18

Ans .

(D) 2 4 3 13 7 6 15 17 20 18 18

Explanation :
Use In-order Traversal i.e Left–Root–Right. following this we have first root at 15, then left sub tree root at 13, then left subtree root at 4, then left is 2 and so on which results in 2 4 3 13 7 6 15 17 20 18 18

Q39. An ideal sort is an in-place-sort whose additional space requirement is _________________

(A) O(log2n)

(B) O(nlog2n)

(D) O(n)

Ans .

Explanation :

Q40. Which of the following is not a congestion policy at network layer?

(A) Flow Control Policy

(B) Packet Discard Policy

(D) Routing Algorithm

Ans .

(A) Flow Control Policy

Explanation :

Q41. Loop unrolling is a code optimization technique:

(A) that avoids tests at every iteration of the loop

(B) that improves performance by decreasing the number of instructions in a basic block.

(D) that reorders operations to allow multiple computations to happen in parallel.

Ans .

(A) that avoids tests at every iteration of the loop

Explanation :
Loop unrolling is a compiler optimization applied to certain kinds of loops to reduce the frequency of branches and loop maintenance instructions. It is easily applied to sequential array processing loops where the number of iterations is known prior to execution of the loop.
The general idea of loop unrolling is to replicate the code inside a loop body a number of times. The number of copies is called the loop unrolling factor. The number of iterations is divided by the loop unrolling factor.

Q42. What will be the hexadecimal value in the register ax (32-bit) after executing the following instructions?
Mov al, 15
Mov ah, 15
Xor al, al
Mov cl, 3
Shr ax, cl

(A) 0F00 h

(B) 0F0F h

(D) FFFF h

Ans .

Explanation :

Q43. Which of the following statements is false?

(A) Top-down parsers are LL parsers where first L stands for left-to-right scan and second L stands for a leftmost derivation.

(B) (000)* is a regular expression that matches only strings containing an odd number of zeroes, including the empty string.

(D) The class of context-free languages is closed under reversal. That is, if L is any context-free language, then the language LR={WR:wϵL} is context free.

Ans .

(B) (000)* is a regular expression that matches only strings containing an odd number of zeroes, including the empty string.

Explanation :

Q44. System calls are usually invoked by using:

(A) A privileged instruction

(B) An indirect jump

(D) Polling

Ans .

Explanation :

Q45. The _______________ transfers the executable image of a C++ program from hard disk to main memory.

(A) Compiler

(B) Linker

(D) Loader

Ans .

(D) Loader

Explanation :

Q46. In software testing, how the error , fault and failure are related to each other?

(A) Error leads to failure but fault is not related to error and failure

(B) Fault leads to failure but error is not related to fault and failure

(D) Fault leads to error and error leads to failure

Ans .

Explanation :

Q47. Which of the following is not a software process model?

(A) Prototyping

(B) Iterative

(D) Glassboxing

Ans .

(D) Glassboxing

Explanation :

Q48. How many solutions are there for the equation x+y+z+u=29 subject to the constraints that x≥1, y≥2, z≥3 and u≥0?

(A) 4960

(B) 2600

(D) 8855

Ans .

(B) 2600

Explanation :
We let y1=x-1, y2=y-2, y3=z-3, y4=u-0
We count the number of solutions for y1+y2+y3+y4=29-6=23
n=4, r=23
The number of solutions is C(n+r-1, r) = C(4+23-1, 23)
= C(26,23) = C(26,3) = 26x25x24/1x2x3 = 2600

Q49. A unix file system has 1-KB blocks and 4-byte disk addresses. What is the maximum file size if i-nodes contain 10 direct entries and one single, double and triple indirect entry each?

(A) 32 GB

(B) 64 GB

(D) 1 GB

Ans .

Explanation :
block = 2^10
block pointer size = 4B
entries possible in block = 2^10/2^2 = 256
direct pointer gives = 10 * 256 = 10 blocks
single indirect gives = 256 * 256 = 2^8 blocks
double indirect gives = 256 * 256 * 256 = 2^16 blocks
triple indirect gives = 256 * 256 * 256 * 256 = 2^24 blocks
total = 10 blocks + 2^8 blocks + 2^16 blocks + 2^24 blocks = 16843018 blocks
= 16843018 * 1024 = 17247250432 ≈ 16 GB

Q50. ______________ uses electronic means to transfer funds directly from one account to another rather than by cheque or cash?

(A) M-Banking

(B) E-Banking

(D) C-Banking

Ans .

(B) E-Banking

Explanation :

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