UGCNET Computer Science Dec 2013 Paper II

Q1. When data and acknowledgement are sent in the same frame, this is called as

(A) Piggy packing

(B) Piggy backing

(D) Good packing

Ans .

(B) Piggy backing

Explanation :

Q2. Encryption and Decryption is the responsibility of _____________ Layer .

(A) Physical

(B) Network

(D) Datalink

Ans .

Explanation :

Q3. An analog signal carries 4 bits in each signal unit. If 1000 signal units are sent per second, then baud rate and bit rate of the signal are ___________________ and ____________________

(A) 4000 bauds \ sec & 1000 bps

(B) 2000 bauds \ sec & 1000 bps

(D) 1000 bauds \ sec & 4000 bps

Ans .

(D) 1000 bauds \ sec & 4000 bps

Explanation :
Bit rate is the number of bits per second. Baud rate is the number of signal units per second. Baud rate is less than or equal to the bit rate. Baud rate = 1000 bauds per second (baud/s) Bit rate = 1000 x 4 = 4000 bps

Q4.The VLF and LF bauds use ______________ propagation for communication.

(A) Ground

(B) Sky

(D) Space

Ans .

(A) Ground

Explanation :
VLF (Very Low Frequency) LF (Low Frequency) In general there are three type of propagation.1.Ground Propagation 2.Sky propagation 3.Line-of-sight propagation. In ground propagation, radio waves travel through the lowest portion of the atmosphere. These low-frequency signals travel in all directions from the transmitting antenna.

Q5.Using the RSA public key crypto system, if p=13, q=31 and d=7, then the value of e is

(A) 101

(B) 105

(D) 107

Ans .

Explanation :
Basic RSA Algorithm: 1. Choose two primes, p & q. 2. Compute n=p*q and z=(p-1)*(q-1). 3. Choose a number relatively prime to z and call it d. 4. Find e such that e*d=1modz. Given p=13, q=31 & d=7, e=? n=p*q=403 z=(p-1)(q-1)=360 e*d=1modz 7e=1mod360, then 7e must be 361, 721, 1081, 1441, etc. Dividing each of these in turn by 7 to see which is divisible by 7, we find that 721/7 = 103, hence e = 103.

Q6. FAN IN of a component A is defined as

(A) Number of components that can call or pass control to component A.

(B) Number of components that are called by component A.

(D) Number of components dependent on component A.

Ans .

(A) Number of components that can call or pass control to component A.

Explanation :

Q7. The relationship of data elements in a module is called

(A) Coupling

(B) Modularity

(D) Granularity

Ans .

Explanation :
Cohesion is the indication of the relationship within module. Coupling is the indication of the relationships between modules. While designing you should strive for high cohesion. While designing you should strive for low coupling.

Q8. Software Configuration Management is the discipline for systematically controlling

(A) the changes due to the evolution of work products as the project proceeds.

(B) the changes due to defects (bugs) being found and then fixed.

(D) all of the above

Ans .

(D) all of the above

Explanation :

Q9. Which one of the following is not a step of requirement engineering ?

(A) Requirement elicitation

(B) Requirement analysts

(D) Requirement documentation

Ans .

Explanation :

Q10. Testing of software with actual data and in actual environment is called

(A) Alpha testing

(B) Beta testing

(D) None of the above

Ans .

(B) Beta testing

Explanation :

Q11. The student marks should not be greater than 100. This is

(A) Integrity constraint

(B) Referential constraint

(D) Feasible constraint

Ans .

(A) Integrity constraint

Explanation :

Q12. GO BOTTOM and SKIP-3 commands are given one after another in a database file of 30 records. It shifts the control to

(A) 28th record

(B) 27th record

(D) 4th record

Ans .

(B) 27th record

Explanation :

Q13. An ER Model includes
I. An ER diagram portraying entity types.
II. Attributes for each entity type
III. Relationships among entity types.
IV . Semantic integrity constraints that reflects the business rules about data not captured in the ER diagram.

(A) I, II, III & IV

(B) I&IV

(D) I & III

Ans .

(A) I, II, III & IV

Explanation :

Q14.Based on the cardinality ratio and participation ___________ associated with a relationship type, choose either the Foreign Key Design, the Cross Referencing Design or Mutual Referencing Design.

(A) Entity

(B) Constraints

(D) Keys

Ans .

(B) Constraints

Explanation :

Q15. Data Integrity control uses _______________

(A) Upper and lower limits on numeric data.

(B) Passwords to prohibit unauthorised access to files.

(D) Data dictionary to find last access of data

Ans .

(B) Passwords to prohibit unauthorised access to files.

Explanation :

Q16. What does the following declaration mean ?
int (*ptr) [10];

(A) ptr is an array of pointers of 10 integers.

(B) ptr is a pointer to an array of 10 integers.

(D) none of the above.

Ans .

(B) ptr is a pointer to an array of 10 integers.

Explanation :

Q17. Which of the following has compilation error in C ?

(A) int n = 32;

(B) char ch = 65;

(D) none of the above

Ans .

(D) none of the above

Explanation :

Q18. Which of the following operators cannot be overloaded in C+ + ?

(A) *

(B) +=

(D) ::

Ans .

(D) ::

Explanation :

Q19. ______________ allows to create classes which are derived from other classes, so that they automatically include some of its "parent's" members, plus its own members.

(A) Overloading

(B) Inheritance

(D) Encapsulation

Ans .

(B) Inheritance

Explanation :

Q20. The correct way to round off a floating number x to an integer value is

(A) y = (int)(x+0.5)

(B) y = int(x+0.5)

(D) y = (int)((int)x+0.5)

Ans .

(A) y = (int)(x+0.5)

Explanation :

Q21. What is the value of the postfix expression ? a b c d + - * (where a = 8, b = 4, c = 2 and d = 5)

(A) -3/8

(B) -8/3

(D) -24

Ans .

(D) -24

Explanation :

Q22. If the queue is implemented with a linked list, keeping track of a front pointer and a rear pointer , which of these pointers will change during an insertion into a non-empty queue?

(A) Neither of the pointers change

(B) Only front pointer changes

(D) Both of the pointers changes

Ans .

Explanation :

Q23. _______________ is often used to prove the correctness of a recursive function.

(A) Diagonalization

(B) Communitivity

(D) Matrix Multiplication

Ans .

Explanation :

Q24. For any B-tree of minimum degree t ≥2, every node other than the root must have atleast ___________ keys and every node can have at most ___________ keys.

(A) t-1, 2t+1

(B) t+1, 2t+1

(D) t+1, 2t-1

Ans .

Explanation :

Q25. Given two sorted list of size 'm' and 'n' respectively. The number of comparison needed in the worst case by the merge sort algorithm will be

(A) m x n

(B) max (m, n)

(D) m + n – 1

Ans .

(D) m + n – 1

Explanation :

Q26. Given the following statements :
S1 : SLR uses follow information to guide reductions. In case of LR and LALR parsers, the look-aheads are associated with the items and they make use of the left context available to the parser.
S2 : LR grammar is a larger sub-class of context free grammar as compared to that SLR and LALR grammars.
Which of the following is true ?

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

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

(D) S1 is correct and S2 is correct.

Ans .

(D) S1 is correct and S2 is correct.

Explanation :

Q27. The context free grammar for the language L = {an bm | n≤m+3, n≥0, m≥0} is

(A) S→aaaA; A→aAb|B, B→Bb|λ

(B) S→aaaA|λ, A→aAb|B, B→Bb|λ

(D) S→aaaA|aaA|aA|λ, A→aAb|B, B→Bb|λ

Ans .

(D) S→aaaA|aaA|aA|λ, A→aAb|B, B→Bb|λ

Explanation :

Q28.Given the following statements :
S1 : If L is a regular language then the language {uv | uϵL, vϵLR} is also regular.
S2 : L = {wwR} is regular language.
Which of the following is true ?

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

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

(D) S1 is correct and S2 is correct.

Ans .

Explanation :

Q29. The process of assigning load addresses to the various parts of the program and adjusting the code and data in the program to reflect the assigned addresses is called _________

(A) Symbol resolution

(B) Parsing

(D) Relocation

Ans .

(D) Relocation

Explanation :

Q30. Which of the following derivations does a top-down parser use while parsing an input string ? The input is scanned from left to right.

(A) Leftmost derivation

(B) Leftmost derivation traced out in reverse

(D) Rightmost derivation

Ans .

(A) Leftmost derivation

Explanation :

Q31. The dual of a Boolean expression is obtained by interchanging

(A) Boolean sums and Boolean products

(B) Boolean sums and Boolean products or interchanging 0's and 1's

(D) Interchanging 0's and 1's

Ans .

Explanation :

Q32. Given that (292)10 = (1204)x in some number system x. The base x of that number system is

(A) 2

(B) 8

(D) None of the above

Ans .

(D) None of the above

Explanation :
6|292
6|48| 4
6|8| 0
6|1| 2
6|1| 1
Solution: (1204)6
So here, x=6

Q33.The sum of products expansion for the function F(x, y, z) = (x + y)z’ is given as

(A) x’y’z + xyz’ + x’yz’

(B) xyz + xyz’ + xy’z’

(D) xyz’ + xy’z’ + x’yz’

Ans .

(D) xyz’ + xy’z’ + x’yz’

Explanation :
Explanation:
Use Boolean identities to expand the product and simplify.
F(x, y, z)=(x + y)z’
=xz’+yz’ Distributive law
=x1z’+1yz’ Identity law
=x(y+y’)z’+(x+x’)yz’ Unit property
=xyz’+xy’z’+xyz’+x’yz’ Distributive law
=xyz’+xy’z’+x’yz’ Idempotent law

Q34. 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 each of the following propositions:
I. ∀ m ∀ n P(m,n),
II. ∃ m ∀ n P(m, n)

(A) Both I and II are true

(B) Both I and II are false

(D) I - true & II – false

Ans .

Explanation :

Q35.Big - O estimate for f(x) = (x + 1) log(x2 + 1) + 3x2 is given as

(A) O(xlogx)

(B) O(x2)

(D) O(x2logx)

Ans .

(B) O(x2)

Explanation :
Big-O notation of f(x)=(x+1) log(x2+1) + 3x2
Note (x+1) is O(x) and x2+1≤2x2 when x>1
So, log x2+1≤log(2x2)=log 2+ log x2=log 2+ 2 log x
≤ 3 log x if x >2
Thus, log x2+1 is O(log x)
The first part of f(x) is O(x log x)
Also, 3x2 is O(x2)
So, f(x) is O(max(x log x, x2))=O(x2) as x log x ≤ x2 for x > 1

Q36. How many edges are there in a forest of t-trees containing a total of n vertices ?

(A) n+t

(B) n-t

(D) nt

Ans .

(B) n-t

Explanation :

Q37. Let f and g be the functions from the set of integers to the set integers defined by
f(x) = 2x + 3 and g(x) = 3x + 2
Then the composition of f and g and g and f is given as

(A) 6x + 7, 6x + 11

(B) 6x + 11, 6x + 7

(D) None of the above

Ans .

(A) 6x + 7, 6x + 11

Explanation :
fog(x)=f(g(x))=f(3x+2)=2(3x+2)+3=6x+7
gof(x)=g(f(x))=g(2x+3)=3(2x+3)+2=6x+11

Q38. If n and r are non-negative integers and n≥r , then p(n + 1, r) equals to

(A) P(n,r)(n+1) / (n+1-r)

(B) P(n,r)(n+1) / (n-1+r)

(D) p(n,r)(n+1) / (n+1+r)

Ans .

(A) P(n,r)(n+1) / (n+1-r)

Explanation :
p(n, r) = n!/(n-r)!
p( n+1, r) = (n+1)!/(n+1-r)!
= (n+1) n! /(n+1-r) (n-r)!
= P(n, r)(n+1)/(n+1-r)

Q39. A graph is non-planar if and only if it contains a subgraph homeomorphic to

(A) K3,2 or K5

(B) K3,3 and K6

(D) K2,3 and K5

Ans .

Explanation :
Kuratowski’s Theorem: A graph is non-planar if and only if it contains a subgraph that is homeomorphic to either K5 or K3,3.

Q40. Which of the following statements are true ?
I. A circuit that adds two bits, producing a sum bit and a carry bit is called half adder.
II. A circuit that adds two bits, producing a sum bit and a carry bit is called full adder.
III. A circuit that adds two bits and a carry bit producing a sum bit and a carry bit is called full adder.
IV . A device that accepts the value of a Boolean variable as input and produces its complement is called an inverter.

(A) I & II

(B) II & III

(D) I, III & IV

Ans .

(D) I, III & IV

Explanation :

Q41. Active X controls are Pentium binary programs that can be embedded in __________

(A) Word pages

(B) URL pages

(D) Web pages

Ans .

(D) Web pages

Explanation :

Q42.Match the following :
a. Wireless Application Environment i. HTTP
b. Wireless Transaction Protocol ii. IP
c. Wireless Datagram Protocol iii. Scripts
d. Wireless iv. UDP

(A) ii iv i iii

(B) iv iii ii i

(D) iii i iv ii

Ans .

(D) iii i iv ii

Explanation :

Q43. Which of the following is widely used inside the telephone system for long-haul data traffic ?

(A) ISDN

(B) ATM

(D) ISTN

Ans .

(B) ATM

Explanation :

Q44. The document standards for EDI were first developed by large business house during the 1970s and are now under the control of the following standard organisation:

(A) ISO

(B) ANSI

(D) IEEE

Ans .

(B) ANSI

Explanation :

Q45. Electronic Data Interchange Software consists of the following four layers:

(A) Business application, Internal format conversion, Network translator, EDI envelope

(B) Business application, Internal format conversion, EDI translator, EDI envelope

(D) Application layer, Transport layer, IP layer, EDI envelope

Ans .

(B) Business application, Internal format conversion, EDI translator, EDI envelope

Explanation :

Q46. Consider a pre-emptive priority based scheduling algorithm based on dynamically changing priority. Larger priority number implies higher priority. When the process is waiting for CPU in the ready queue (but not yet started execution), its priority changes at a rate a = 2. When it starts running, its priority changes at a rate b = 1. All the processes are assigned priority value 0 when they enter ready queue. Assume that the following processes want to execute :
Process ID Arrival Time Service Time
P1 0 4
P2 1 1
P3 2 2
P4 3 1
The time quantum q = 1. When two processes want to join ready queue simultaneously, the process which has not executed recently is given priority. The finish time of processes P1, P2, P3 and P4 will respectively be

(A) 4, 5, 7 and 8

(B) 8, 2, 7 and 5

(D) 8, 2, 5 and 7

Ans .

(B) 8, 2, 7 and 5

Explanation :
T EP Priority After T
00 P1 P1[0] P2[-] P3[-] P4[-]
01 P2 P1[1] P2[0] P3[-] P4[-]
02 P1 P1[1] P2[X] P3[2] P4[-] ........P2 completed at 2
03 P3 P1[2] P2[X] P3[2] P4[2]
04 P4 P1[3] P2[X] P3[3] P4[2]
05 P1 P1[3] P2[X] P3[4] P4[X] .......P4 completed at 5
06 P3 P1[4] P2[X] P3[4] P4[X]
07 P1 P1[4] P2[X] P3[X] P4[X] .......P3 completed at 7
08 -- P1[X] P2[X] P3[X] P4[X] .......P1 completed at 8

Q47. The virtual address generated by a CPU is 32 bits. The Translation Look-aside Buffer (TLB) can hold total 64 page table entries and a 4-way set associative (i.e. with 4- cache lines in the set). The page size is 4 KB. The minimum size of TLB tag is

(A) 12 bits

(B) 15 bits

(D) 20 bits

Ans .

Explanation :
VirtualAddress = 32 bits
PageSize = 4KB = 12 bits
therefore : VPNTag = 20 bits, OffsetTag = 12 bits
TLBEntryLength = VPNTag = 20 bits
TotalTLBEntries = 64,
4-way implies 64/ 4 = 16 sets = 4 bits
therefore : TLBIndex = 4 bits
TLBTag = TLBEntryLength - TLBIndex = 20 - 4 = 16 bits

Q48. Consider a disk queue with request for input/output to block on cylinders
98, 183, 37, 122, 14, 124, 65, 67 in that order . Assume that disk head is initially positioned at cylinder 53 and moving towards cylinder number 0. The total number of head movements using Shortest Seek Time First (SSTF) and SCAN algorithms are respectively

(A) 236 and 208 cylinders

(B) 640 and 236 cylinders

(D) 235 and 252 cylinders

Ans .

(A) 236 and 208 cylinders

Explanation :
SSTF
Initial head position =53
The closest queue to initial head position=65
head moves from 53 to 65=12
head moves from 65 to 67=2
head moves from 67 to 37=30
head moves from 37 to 14=23
head moves from 14 to 98=84
head moves from 98 to 122=24
head moves from 122 to 124=2
head moves from 124 to 183=59
Total head movement=236
SCAN
Initial head position=53 and moving towards 0
head moves from 53 to 37=16
head moves from 37 to 14=23
head moves from 14 to 65=51
head moves from 65 to 67=2
head moves from 67 to 98=31
head moves from 98 to 122=24
head moves from 122 to 124=2
head moves from 124 to 183=59
Total head movement=208

Q49. How much space will be required to store the bit map of a 1.3 GB disk with 512 bytes block size ?

(A) 332.8 KB

(B) 83.6 KB

(D) 256.6 KB

Ans .

(A) 332.8 KB

Explanation :
block size=29x23 bits (512 bytes)
disk size=1.3x230x23 bits (1.3 GB)
n=1.3x233/212=1.3x221 bits=1.3x210x28x23 bits=1.3x28 Kilo Bytes=332.8 KB

Q50. Linux operating system uses

(A) Affinity Scheduling

(B) Fair Preemptive Scheduling

(D) Highest Penalty Ratio Next

Ans .

(B) Fair Preemptive Scheduling

Explanation :
Linux uses two process-scheduling algorithms:
1. A time-sharing algorithm for fair preemptive scheduling between multiple processes
2. A real-time algorithm for tasks where absolute priorities are more important than fairness

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