JT(IT) 2016 PARTB Computer Science
Question 1 
If a random variable takes a finite set of values it is called:
Continuous variate  
Normal variate
 
Discrete variate
 
Exponential variate 
Examples:
number of students present
number of red marbles in a jar
number of heads when flipping three coins
students’ grade level
→ A discrete random variable X has a countable number of possible values.
Example:
Let X represent the sum of two dice.
→ A discrete random variable is one which may take on only a countable number of distinct values such as 0,1,2,3,4,........ Discrete random variables are usually (but not necessarily) counts. If a random variable can take only a finite number of distinct values, then it must be discrete.
Examples of discrete random variables include the number of children in a family, the Friday night attendance at a cinema, the number of patients in a doctor's surgery, the number of defective light bulbs in a box of ten.
Question 2 
In clientserver computing vertical scaling means:
Adding or removing client workstations with only a slight performance impact
 
Migrating servers to a new group of client workstations  
Migrating client workstations to a larger and faster server machine or multi servers  
Combining two or more client workstation groups

→ Vertical Scaling is most commonly used in applications and products of middlerange as well as small and middlesized companies. One of the most common examples of Virtual Scaling is to buy an expensive hardware and use it as a Virtual Machine hypervisor (VMWare ESX).
→ Vertical Scaling usually means upgrade of server hardware. Some of the reasons to scale vertically includes increasing IOPS (Input / Output Operations), amplifying CPU/RAM capacity, as well as disk capacity.
→ However, even after using virtualization, whenever an improved performance is targeted, the risk for downtimes with it is much higher than using horizontal scaling.
Question 3 
If the mean of a poisson distribution is m, then standard deviation of the distribution is:
m^{2}  
m  
2*m  
√m 
Question 4 
The 10Base5 cabling scheme of ethernet uses:
Twisted pairs
 
Fiber optics  
Thin coax
 
Thick coax 
10Base5 is also called thick Ethernet, ThickWire, and ThickNet.
→ The number 10: At the front of each identifier, 10 denotes the standard data transfer speed over these media  ten megabits per second (10Mbps).
→ The word Base: Short for Baseband, this part of the identifier signifies a type of network that uses only one carrier frequency for signaling and requires all network stations to share its use.
→ The segment type or segment length: This part of the identifier can be a digit or a letter:
 Digit  shorthand for how long (in meters) a cable segment may be before attenuation sets in.
For example, a 10Base5 segment can be no more than 500 meters long.
 Letter  identifies a specific physical type of cable.
For example, the T at the end of 10BaseT stands for twistedpair.
Question 5 
The standard deviation of binomial distribution with n observations and probability of success p, probability of failure is q is:
√npq
 
Pq  
Np  
√pq 
The binomial distribution for a random variable X with parameters n and p represents the sum of n independent variables Z which may assume the values 0 or 1. If the probability that each Z variable assumes the value 1 is equal to p, then the mean of each variable is equal to l*p + 0*(lp) = p, and the variance is equal to p(lp).
By the addition properties for independent random variables, the mean and variance of the binomial distribution are equal to the sum of the means and variances of the n independent Z variables, so
These definitions are intuitively logical. Imagine, for example 8 flips of a coin. If the coin is fair, then p = 0.5. One would expect the mean number of heads to be half the flips, or np = 8*0.5 = 4.
The variance is equal to np(lp) = 8*0.5*0.5 = 2.
Question 6 
One of the adhoc solutions to count to infinity problem in network routing is:
The split horizon hack
 
Flow based routing  
Flooding
 
Shortest path routing

1. Route Poison
2. The split horizon hack
Question 7 
The normal curve is symmetrical about its:
Standard deviation  
Mean
 
Variance  
Probability

The probability density of the normal distribution is
Where
• μ is the mean or expectation of the distribution (and also its median and mode).
• σ is the standard deviation, and
• 2 is the variance
Question 8 
Given a bit rate of b bits/sec, the time required to send 16 bits is:
16*b sec
 
16/b sec
 
16^{b} sec  
b^{16} sec

The data rate R is a function of the duration of the bit or bit time (T_{B}).
R = 1/T_{B}
Question 9 
The density of uniform distribution over the interval ⍺ < a < b < ⍺ is given by:
f(x) = λe^{λx} , x>=0
 
f(x) = q^{k}p  
f(x) = 1/(ba), a  
f(x) = (⍺/c)x^{⍺1}

The values of f(x) at the two boundaries a and b are usually unimportant because they do not alter the values of the integrals of f(X) dX over any interval, not of X f(X) dX or any higher moment. Sometimes they are chosen to be zero, and sometimes chosen to be 1/(b – a). The latter is appropriate in the context of estimation by the method of maximum likelihood. In the context of Fourier analysis, one may lake the value of f(a) to be 12(b – a), since then the inverse transform of may integral transform of this uniform function will yield back the function itself, rather than a function which equal ‘almost everywhere’, i.e except on a set of points with zero measure. Also, it is consistent with the sign function which has no such ambiguity.
In terms of mean and variance σ^{2}, the probability density may be written as:
Question 10 
The built in HTTP request method to request to read a web page is:
HEAD  
PUT
 
GET
 
POST 
The request method indicates the method to be performed on the resource identified by the given RequestURI. The method is casesensitive and should always be mentioned in uppercase. The following table lists all the supported methods in HTTP/1.1.
Question 11 
Exponential distribution is special case of ____ distribution.
Theta  
Alpha  
Beta  
Gamma 
Question 12 
The traditional cryptographic cipher that records the letters but do not disguise them is:
Substitute cipher  
Onetime pads
 
Secret key algorithms
 
Transposition cipher 
Also this code can be easily broken.
Question 13 
0  
1  
1  
⍺ 
Question 14 
The segmentation memory management scheme suffers from:
External fragmentation  
Internal fragmentation
 
Starvation
 
Ageing

Paging avoids external fragmentation but still it suffers from internal fragmentation. < br> • Internal fragmentation is the wasted space within each allocated block because of rounding up from the actual requested allocation to the allocation granularity.
• External fragmentation is the various free spaced holes that are generated in either your memory or disk space. External fragmented blocks are available for allocation, but may be too small to be of any use.
• Resource starvation is a problem encountered in concurrent computing where a process is perpetually denied necessary resources to process its work. Starvation may be caused by errors in a scheduling or mutual exclusion algorithm.
• Ageing is a scheduling technique used to avoid starvation.
Question 15 
The mean, mode and median are connected by the empirical relationship:
Meanmode = 2(meanmedian)
 
Meanmode = 3(meanmedian)  
Meanmode = (meanmode)/2
 
Meanmode = (meanmode)/3

Mode = mean  3 [mean  median]
Mode = 3 median  2 mean
and Median = mode + ⅔ [meanmode]
Question 16 
The signed 2’s complement representation of 33 is:
11011111
 
00100001  
01011111
 
10100001

Step2: Perform 2’s complement.
Question 17 
The root mean square deviation when measured from the mean is:
Greatest
 
Positive
 
Least
 
Negative

Question 18 
Using signed 2’s complement subtraction the result of 1111101011110011 is:
10000111  
00000111  
10001101  
00001101 
11110011 → 243(Decimal)
Step1: convert signed number into 2’s complement
11110011
00001100 → (1’s complement)
+1

00001101 → (2’s complement)
Step 2: Add 11111010 into 2’s complement number
11111010
00001101

00000111 → solution
Question 19 
The values which divide the frequency into four equal parts are called:
Coefficient of variance
 
Range  
Dispersion  
Quartiles

Question 20 
A digital computer has a memory unit of 64k x 16 and a cache memory of 2^{10} words. The cache uses Direct mapping with a block size of four words. How many bits are there in the tag, index and block Fields of address format?
1, 6, 16
 
2^{8}
 
6, 8, 2  
2^{4}

Therefore Physical address = PA = 16 bits
No. of blocks in cache = cachesize/blocksize = 2^{10}/ 2^{2} = 2^{8} = 256
∴ 8 bits for block
As block size = 4 words = 2^{2} words
∴ 2 bits for offset
Now, tag = 16  8  2 = 6 bits
a) Tag = 6 bits, Index = block = 8 bits, offset = word = 2 bits
Question 21 
How many 3 digit numbers are there with all different odd digits?
16  
48  
54  
60 
• But for every hundreds, maximum of 4 tens is possible (avoiding the duplicate of digit used in hundreds)
• And each of these 4 tens, maximum of 3 units is possible (avoiding the duplicate of digits used in tens)
• 5 * 4 * 3 = 60
Question 22 
A computer employs RAM chips of 256x8 ROM chip of 1024x8. The computer system needs 2k bytes of RAM, 4k bytes of ROM and 4 interface units each with four registers. A memory mapped I/O configuration is used. How many RAM and ROM chips are used?
4, 16  
16, 4  
4, 8  
8, 4 
Memory size required = 2k bytes = 2*1024*8 bits
= [Memory size required] / [Size of RAM chip] = 8
→ Size of ROM chip is = 1024*8
Memory size required = 4k bytes = 4*1024*8 bits
= [Memory size required] / [Size of ROM chip] = 4
Question 23 
In how many ways can a committee of 4 people be chosen from a group of 12?
495  
595
 
395
 
295

C(n,r) = C(12,4)
= 12! / [(4!(12−4)!)]
= 495
Hence, a committee of 4 people be selected from a group of 12 people in 495 ways.
Question 24 
Which of the following method is used for repetitive in which each action is started in terms of a previous result:
Recursion
 
Iteration
 
Looping
 
Structures

Question 25 
A straight line which cuts a curve on two points at an infinite distance from the origin and yet is not itself wholly at infinity is called:
Spiral
 
Asymptote
 
Parallel
 
Polar

Question 26 
Which of the following is wrong while inserting a node in the beginning of list?
Obtain a node from available list
 
Make the next pointer of the current head pointer to new node  
Make the node pointer of the list pointer to new node
 
Make the next pointer of the new node pointer to current head of the list

• Option B, C and D: It shows actual procedure to insert a node at beginning. So, Option A is wrong
Question 27 
If k parallel lines of a determinant Δ become identical when x=a, then ____ is a factor of Δ.
(xa)+(k+1)
 
(xa)/(k1)
 
(xa)*(k+1)
 
(xa)^{(k1)}

• In general, if k rows (or k columns) become identical (x=a) when a is substituted for x, then (xa)^{r1} is a factor of D.
Question 28 
A minimal subgraph G’ of G such that V(G’)=V(G) and G’ is connected is called:
A spanning tree
 
A connected graph
 
A directed graph
 
A biconnected component 
Question 29 
Rank of nonsingular square matrix of order r is:
r  
0  
r1  
1 
• Rank of singular matrix is less than “r”.
Question 30 
For the recurrence relation T(n) = 2 + T(n  1), where T(0)=2, T(n)=?
n^{2}
 
2n+2  
log(n)  
2^{n} 
T(0) = 1
T(n1) = T(n11)+1
T(n) = [T(n2)+1] +1 = T(n2)+ 2
T(n2) = T(n21)+1
T(n) = [T(n3)+1]+1
= T(n3)+3
= T(n) = T(nk)+ k
Note: Let k = n
Then T(n) = T(0) + n = 1 + n
∴ O(n)
Question 31 
The newton’s Raphson iterative formula for finding 1/N is:
½(x_{n} + N/x_{n})  
x_{n}(1  Nx_{n})
 
½(x_{n}+1/Nx_{n})  
1/k((k1)x_{n} + N/x_{n}^{k1})

• The iterations x_{k+1} = x_{k} − ( f(x_{k})/ f ′(x_{k}) ) are called Newton’s iterations.
Question 32 
Portability is not a quality factor of:
Software coding
 
Software design
 
Software Process  
Software testing

This model classifies all software requirements into 11 software quality factors. The 11 factors are grouped into three categories – product operation, product revision, and product transition factors.
1. Product operation factors − Correctness, Reliability, Efficiency, Integrity, Usability.
2. Product revision factors − Maintainability, Flexibility, Testability.
3. Product transition factors − Portability, Reusability, Interoperability.
Question 33 
The number of strips required in simpson’s 3/8^{th} rule is a multiple of:
1  
2  
3  
6 
Area = 3h/ 8 [( a + 3 b + 3 c + d )]
Simpson's Second Rule:
Multipliers:
Question 34 
Travelling salesperson problem belongs to which category of problems?
Satisfiable
 
Non Solvable
 
Decision  
Optimization

Question 35 
A declarative sentence which is either true(1) or false(0) is called:
Lattice
 
Tautology
 
Contradiction
 
Proposition

• Sentences that assert a fact that could either be true or false.
Question 36 
If customer is to be involved in all phases of software development, which software model can be selected:
Prototype model
 
Waterfall model
 
RAD model
 
Component model

Question 37 
The points at which the function attains extreme values are called:
Turning points  
End points
 
Higher points  
Extreme points

Question 38 
In page replacement, ‘adding more frames may cause more page faults’ is referred to as:
Thrashing
 
Belady’s anomaly
 
Banker’s anomaly
 
Ageing 
Question 39 
If f(x) = ax^{2} + bx + c the f(x(b/2a)) is:
An even function for all a except a=0
 
An even function for all a
 
Neither even nor odd
 
An odd function for all a except a=0 
• A function f is odd if the graph of f is symmetric with respect to the origin. Algebraically, f is odd if and only if f(x) = f(x) for all x in the domain of f.
Question 40 
____ is an IEEE 1003.1C standard API for thread creation and synchronization in operating system.
Mac OS X
 
Solaris
 
POSIX
 
Kernel 
Question 41 
The sum of n terms of 1/(1*2) + 1/(2*3) + 1/(3*4) + ... is
(n+1)/n
 
n/(n+1)
 
n/(2n+1)
 
(2n+1)/n

where
1st term = 1/(1*2)
2nd term = 1/(2*3)
3rd term = 1/(3*4)
.
.
.
.
nth term = 1/(n*(n+1))
nth term = 1/(n*(n+1))
i.e. the kth term is of the form 1/(k*(k+1))
which can further be written as kth term = 1/k  1/(k+1)
So, sum upto n terms can be calculated as:
(1/1  1/1+1) + (1/2  1/2+1) + (1/3  1/3+1) + ......... + (1/n1  /1n) + (1/n  1/n+1)
= (1  1/2) + (1/2  1/3) + (1/3  1/4) + ......... + (1/n1  1/n) + (1/n  1/n+1)
= 1  1/n+1
= ((n+1)  1)/n+1
= n/n+1
Question 42 
If a system has multiple instances of resources, to avoid deadlock which of the following algorithms is used?
Deadlock avoidance algorithm
 
Aging algorithm
 
Resource allocation graph algorithm
 
Banker’s algorithm 
Banker's algo can be applied even when Resourcesystem have multiple instances of each resource type. It can also be applied when Resourcesystem have single instance of each resource type But in that case, It would be less efficient than ResourceAllocation Graph Algorithm.
Question 43 
How many integers are between 1 and 200 which are divisible by any one of the integers 2,3 and 5(Hint: use set operation)?
125  
145  
146  
136 
B) numbers divisible by 3: 200/3 = 66
C) numbers divisible by 5: 200/5 = 40
Counting twice:
AB) numbers divisible by 6: 200/6 = 33
AC) numbers divisible by 10: 200/10 = 20
BC) numbers divisible by 15: 200/15 = 13
Counting 3 times:
ABC) numbers divisible by 30: 200/30 = 6
Total of numbers = A + B + C  AB  AC  BC + ABC = 100 + 66 + 40  33  20 13 + 6 = 146
Question 44 
Which of the following is not a CPU scheduling criteria:
Dispatch latency  
CPU utilization
 
Throughput  
Turnaround time

Note: The time taken by the dispatcher to stop one process and start another running is known as dispatch latency.
Question 45 
Which of the following checks are not included in semantic analysis done by the compiler:
Type checks
 
Spelling checks
 
Uniquencess checks  
Flow of control checks

1. Scope resolution
2. Type checking
3. Arraybound checking
Question 46 
To add attributes to an existing relation __ commands is used:
Update table
 
Alter table
 
Change table
 
Add table 
SQL allows the owner of the database relation to change it by:
1. Adding one or more attributes to the relation.
2. Removing one or more attributes from the relation.
3. Adding one or more constraints to the relation.
4. Removing one or more constraints from the relation.
Question 47 
In boolean algebra, (x ⋀ y)’ = x’ V y’ and (x V y)’ = x’ ⋀ y’ is known as ___ law.
Demorgan’s law
 
Absorption
 
Dominance
 
Idempotent

1. The negation of a disjunction is the conjunction of the negations.
2. The negation of a conjunction is the disjunction of the negations.
Question 48 
A relation that is not of connected model but is made visible to a user as a virtual relation is called:
Table  
Query
 
View
 
Joined relations 
→ A view contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.
→ You can add SQL functions, WHERE, and JOIN statements to a view and present the data as if the data were coming from one single table.
CREATE VIEW Syntax:
CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;
Note:
A view always shows uptodate data! The database engine recreates the data, using the view's SQL statement, every time a user queries a view.
Question 49 
In algebra of logic, the conjunction of two tautologies is:
Contradiction
 
Tautology
 
Negation  
Disjunction

1. The negation of a contradiction is a tautology.
2. The disjunction of two contingencies can be a tautology.
3. The conjunction of two tautologies is a tautology.
Question 50 
In transaction management od database, ‘After a transaction completes successfully the changes it has made to the database persists even if there are system failures’. This property is referred to as:
Atomicity  
Consistency  
Isolation
 
Durability 
• If a transaction updates a chunk of data in a database and commits, then the database will hold the modified data.
• If a transaction commits but the system fails before the data could be written on to the disk, then that data will be updated once the system springs back into action.
Question 51 
Harmonic function  
Laplace equation
 
Wave equation
 
Homogeneous

Note that the wave equation can be factored as
Question 52 
For the relation loan(loan_number, branch_name, amount), the query{tt ∈ loan ∧ t[amount] > 1200} gives:
The loan_number, branch_name and amount for loans over $1200
 
The loan_number for each loan of an amount greater than $1200
 
The branch_name for each loan of an amount greater than $1200
 
The amount for each loan of an amount greater than $1200 
customer (customername, customerstreet, customercity)
account (accountnumber, branchname, balance)
loan (loannumber, branchname, amount)
depositor (customername, accountnumber)
borrower (customername, loannumber)
→ The loannumber, branchname, and amount for loans of over $1200
{t  t ∈ loan ∧ t[amount] > 1200}
Question 53 
The number of two digit numbers divisible by the product of digits is:
8  
14  
13  
5 
12=1*2=2 which is a factor of 12
15=1*5=5 which is a factor of 15
24=2*4=8 which is a factor of 24
36=3*6=12 which is a factor of 36
Question 54 
In concurrency control a situation where ‘ A transaction may be waiting for an xlock on an item, while a sequence of other transactions request and are granted on slock on the same item’. May lead to:
Deadlock
 
Starvation  
Conflict  
Lock failure

Reasons of Starvation:
1. If waiting scheme for locked items is unfair. ( priority queue )
2. Victim selection. ( same transaction is selected as a victim repeatedly )
3. Resource leak. (Via denialofservice attack)
Question 55 
If a relation < from A={1,2,3,4} to B={1,3,5} i.e., (a,b)∈R if a < b, then R^{1} is:
{(1,3)(1,5)(2,3)(2,5)(3,5)(4,5)}
 
{(3,1)(5,1)(3,2)(5,2)(5,3)(5,4)}  
{(3,3)(3,5)(5,3)(5,5)}
 
{(3,3)(3,4)(4,5)} 
Question 56 
Which of the following is not an entity reference in XML?
&qt  
&
 
<  
>

They are introduced to avoid the ambiguity while using some symbols.
For example, an ambiguity is observed when less than ( < ) or greater than ( > ) symbol is used with the angle tag (<>).
Character entities are basically used to delimit tags in XML.
Following is a list of predefined character entities from XML specification. These can be used to express characters without ambiguity.
Ampersand − &
Single quote − '
Greater than − >
Less than − <
Double quote − "
Question 57 
If a lattice (L,R) has a greatest and least element then it is said to be:
Sub Lattice  
Complemented Lattice
 
Bounded Lattice
 
Distributive Lattice

→ A bounded lattice is an algebraic structure of the form (L, ∨, ∧, 0, 1) such that (L, ∨, ∧) is a lattice, 0 (the lattice's bottom) is the identity element for the join operation ∨, and 1 (the lattice top) is the identity element for the meet operation ∧.
→ Let 'L' be a lattice w.r.t R if there exists an element I∈L such that (aRI)∀x∈L, then I is called Upper Bound of a Lattice L.
Similarly, if there exists an element O∈L such that (ORa)∀a∈L, then O is called Lower Bound of Lattice L.
Question 58 
____ element is used to create destination anchors in HTML?
< d >  
< a >  
< da >  
< ad > 
• This section introduces the link (or hyperlink, or Web link), the basic hypertext construct. A link is a connection from one Web resource to another. Although a simple concept, the link has been one of the primary forces driving the success of the Web.
• A link has two ends  called anchors  and a direction. The link starts at the "source" anchor and points to the "destination" anchor, which may be any Web resource (e.g., an image, a video clip, a sound bite, a program, an HTML document, an element within an HTML document, etc.)
Question 59 
For the context free grammar G:
R → XRXS, S → aTbTa, T → XTXXϵ X → ab
The strings which are not in L(G) are:
ab,ba,aab
 
abb,aabab
 
a,b,aa
 
a,b,ϵ

Question 60 
The sum of the series: (1/2) + (1/3) + (1/4)  (1/6) + (1/8) + (1/9) + (1/16)  (1/12) + ... + α is:
(1/2)  log(√2)^{3}
 
1 + log(√2)^{3}
 
3/2  
1/2 + log(√2)^{3}
