HSST

(In the question paper with Question Booklet Code D; the following Questions are erroneous.

Answers given by PSC is underlined)

12. Which is not possible in a thread

A.Ready B.Wait C.Suspended D. Running

Correct is B

[Comment:- “Thread exists in several states. A thread can be running .It can be ready to run as soon as it gets CPU time. A running state can be suspended”. It is quoted from "The Complete Reference JAVA 2" by Herbert Schildt –fourth Edn. page 273. ]

18.Bankers algorithm in resource allocation deals with

A. Dead lock prevention B.Dead lock recovery C. Dead lock avoidance

D. Mutual Exclusion.

Correct is C

[Comment:- “The deadlock avoidance algorithm that we describe next is applicable to such a system,but is less efficient than the resource –allocation graph scheme. This algorithm is commonly known as Bankers algorithm” .It is quoted from "Operating System Concepts" Sixth Edition by Silberschatz]

19.Thrashing Occurs in

A. large computers B.a natural consequence of virtual memory system

C.can always be avoided by swapping D. Poor Paging Algorithm

Correct is D

[Comment:- As per "Operating System Concepts" Sixth Edition by Silberschatz, ‘A process is thrashing if it is spending more time paging than executing’(ie,page fault occurs frequently). If we work with a poor paging algorithm it must be engaged in paging activity almost in all time. No. of Page faults depends on paging algorithm. As poor paging algorithm is used page fault occurs frequently. That is thrashing.

Given answer has no role in thrashing. Apart from all, it not even matches sentential to the given question. That is, “ Thrashing Occurs in can always be avoided by swapping” . What does it mean????]

31.Error correction in Data Link Layer is achieved by

A. Equalization B.Cyclic Redundancy Code C.Hamming Code D.Bit stuffing

Correct is C

[Comment:-‘Cyclic Redundancy Code’ Error detection Code only. Hamming Code is an error correcting code used in Data link layer.Please refer "Computer Networks" fourth Edition by Andrew. S. Tanenbaum page 193]

38.In any undirected graph ,the sum of degree of all nodes is

A. Must be even B.is always ODD C. need not be even D.is twice the number of edges

Answer : No Answer[correct is A&D]

[Comment:- D is true. But it also implies option A is true. Because twice of any number “must be even” ]

48. Which is Universal Gate?

A. AND B. NOR C.XOR D.NOT

Correct is B

[Comment: A universal gate is one from which all other basic gates can be formed. NAND gate& NOR gate are called Universal]

49. How many NAND gates are needed to perform X.Y ?

A. 3 B. 4 C. 2 D.1

[Comment:- Connect two NAND gates serially]

For qns 48&49;refer “Digital fundamentals" by Floyd, “Digital fundamentals" by Floyd&Jain

51.Which is the access method to take data from tape memory

A. Direct B. Sequential C. Parallel D. Serial

[Comment: “ Sequential access is based on a tape model of file” it is quoted from "Operating System Concepts" Sixth Edition by Silberschatz page 380

Please refer any fundamental books.eg:- "Computer Fundementals" by P.K Sinha]

52.8241 Code is

A. BCD Code B. Gray Code C. Excess 3 Code D. ASCII

[Comment:- BCD Code is 8421 code(not 8241); Gray code and Excess3 code are unweighted codes. Please refer "Computer System Architecture" by M.Morris Mano ]

53. 1001000010011001 base 2 is equivalent in base 16 is

A. 9899 B. 9989 C.8999 D. 9999

No answer

[Comment : To convert a binary number in to Hexadecimal(base 16) .Binary number is grouped(with 4 digits in agroup) from left. Then each group’s decimal equivalent together gives answer. Here 1001000010011001 is grouped as 1001, 0000, 1001, 1001. decimal equivalent of each group is 9 0 9 9. Hence 9099 base 16 in the answer]

61. Which is programmable interval timer?

A. 8253 B. NE555 C. 8275 D. 8251

Correct anser is A

[Comment:- just use the link http://en.wikipedia.org/wiki/intel_8253

Or refer ."Computer fundamentals:architecture and organization " by B.RAM

"A formal description of intel 8253" by A.J.H.M Peeli]

72.Recursively Enumerable Languages are closed under

A. Union B. Intersection C. Complementation D. Concatenation

[No Answer[correct is A&B]

[Comment:- Therom 11.3 in "Introduction to formal languages and Automata" by Peter Linz “ says “There exists a recursively enumerable language whose complement is not recursively enumerable”

Use the link to get clarification http://alleystoughton.us/forlan/book-and-slides/slides-5.2.pdf

73. The grammar that produce more than one parse tree for same sentence is

A. Ambiguous B. Un ambiguous C. Complementation D. Concatenation Intersection

(Correct is A)

[Comment:- "Introduction to formal languages and Automata" by Peter Linz “ definition 5.5 of Ambiguous grammar is enough]

81. In data manipulation the first element of T[5] is

A. T[1] B. T[0] C. T[5] D. T[3]

Correct is B

[Comment:- Unless explicitly specified first element is stored at 0^th index.

Clearly it is depicted in "Computer Science" for Higher Sceondary Course Class XI, prepared by SCERT ,Thiruvananthapuram,Govt of Kerala,Dept of Education page 140]

89. Who designed the first Digital Computer using Binary system

A, Blaise Pascal B. Agutha Ada C. Isaac Newton D. Sakunthala Devi

[Comment : B,C,&D are persons not related to the design of computers.

http://en.wikipedia.org/wiki/history_of_computer_ science]

91. Which of the following preposition is a tautology?

A. P U Q→ P B. P →(Q→ P) C. PU(Q→P) D. None of these

Answer is B

[Comment:- if a an expression is Tautology ;its all truth values are TRUE.

Proof:-

P Q Q->P P->(Q->P)

F F T T

F T F T

T F T T

T T T T

Hence the answer

92. p→q→r is equivalent to

A. p→q→r B. p→(q→r) C. pU(q→r) D. None of these

Answer is A

[Comment:- No explanation is needed. All we know that p→q→r is equal to p→q→r

Then how ‘ None of these’ comes]

93. Give the name of linear list in which elements can be added at ends but not in the middle

A. Array B. Queue C.Tree D. Cicrcular Queue

[Comment:- In Array we can insert elements any where . Hence A is wrong

By definition of Queue itself. Queue is a datastructure to which elements can be added at one end only called rear and deleted from the other end called front. Hence B is wrong

In Tree values are inserted at branches.Hence C is wrong]

26. Resolution of Video Display Unit does not depend on

A. Raster Scan rate B. Band width C. Vertical and Horizontal Scan D. Screen Size

Answer is B

[Comment: Resolution is expressed as horizontal &vertical screen values(Eg:-800x600 pixel). Hence screen size has significance. But Bandwidth is a term related to data communication]

27. 26. Resolution of Video Display Unit does not depend on

A. Raster Scan rate B. Band width C. Vertical and Horizontal Scan D. Screen Size

[Comment: It is same question pasted ….! Hence it must be removed]

45. The Equations will have:

A. no unique solution B. Only one solution C. has only two solution D. has infinite

[Comment:It carries no sense. Those who prepared the question forgot to add an equation in the question.

Equations can be of may types linear,quadratic,cubic,degree4,degree5,………degree n. All these have different number of solutions. Ie,1 solution,2solution, 3solution, 4solution, 5solution,……… n solution]

Sheeba

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