algorithms question answers set1
TRANSCRIPT
-
7/23/2019 Algorithms Question Answers Set1
1/42
PAPER-VII
ALGORITHMS
What is time and space complexity?
Ans:- Time complexitya function which
describes the amount of time an algorithm
akes in terms of the amount of i/p to thealgorithm.
Space complexitya function whichdescribes the amount of memory (space)
an algorithm takes in terms of the amount
of input to the algorithm.
Dijkstra's Algorithm:-The time required
by Dijkstra's algorithm is O(|V|2). It wil
be reduced to O(|E|log|V|) if heap is used
-
7/23/2019 Algorithms Question Answers Set1
2/42
o keep {v in V\Si: L(v) < infinity}.
Prim's Algorithm:-The time required by
Prim's algorithm is O(|V|2). It will beeduced to O(|E|log|V|) if heap is used to
keep {v in V\Si: L(v) < infinity}.
Kruskal algorithm:- The time requiredby Kruskal's algorithm is O(|E|log|V|).
Travelling Salesman Problem.:-It is a
raditional issue that has to do witmaking the most efficient use of resource
while at the same time expending the leas
amount of energy in that utilization. The
designation for this type of problem hail
back to the days of the travelingsalesman
who often wished to arrange travel in a
manner that allowed for visiting the mos
-
7/23/2019 Algorithms Question Answers Set1
3/42
owns without having to double back and
cross into any given town more than once
Poission process:-It is a collectio{N(t) : t 0} of random variables
where N(t) is the number of events tha
have occurred up to time t (starting fro
ime 0). The number of events betweeime aand time bis given asN(b) N(a
and has aPoisson distribution
Each realization of the process {N(t)} i
a non-negative integer-valued step
function that is non-decreasing, but fo
ntuitive purposes it is usually easier to
hink of it as a point pattern on [0,) (thepoints in time where an event occurs)
The Poisson process is a continuous-time
process. A Poisson process is a pure
birth process, the simplest example o
http://en.wikipedia.org/wiki/Realization_(probability)http://en.wikipedia.org/wiki/Poisson_distributionhttp://en.wikipedia.org/wiki/Random_variable -
7/23/2019 Algorithms Question Answers Set1
4/42
a birth-death process.
Inclusion Principal:- The principle thatfA and B are finite sets, the number o
elements in the union of A and B can be
obtained by adding the number o
elements in A to the number of elementn B, and then subtracting from this sum
s the number of elements in the
ntersection ofAandB.
Propositional Satisfiability Problem:-A
propositional satisfiability problembriefly called SAT, consists of a
formula F 2 L(R), and is the problem to
decide whether F is satisfiable.
http://en.wikipedia.org/wiki/Birth-death_process -
7/23/2019 Algorithms Question Answers Set1
5/42
SAT is a combinatorial decisio
problem.
1. Decision variant yes/no
answer .2. Search variant find a model i
F is satisfiable
BFS AND DFS
Breadth-first Search:-
The general idea behinda breadth-first search beginning
at a starting vertex A is as
follows. First we process the
-
7/23/2019 Algorithms Question Answers Set1
6/42
starting vertex A.Then
we process all the neighbors
of A.Then we process allthe neighbors of neighbors
of AAnd so on. Naturally we
need to keep track of theneighbors of a
vertex, andwe need toguarantee
that no vertex is processed twiceThis is accomplished by using a
QUEUE to hold vertices that arc
waiting to he processed, and bya field STATUS which tells us the
current status
-
7/23/2019 Algorithms Question Answers Set1
7/42
of a vertex.The algorithm follows
Algorithm (Breadth-first Search):This algorithm executes a breadth-firstsearch on a graph G beginning with astarling vertex A
Step 1. Initialize all vertices to theeady state (STATUS = 1)
Step 2. Put the starting vertex A inQUEUE and change the status of A tohe waiting state (STATUS =2).
Step3. Repeat Steps 4 and 5 untilQUEUE is empty.
Step 4.Remove the front vertex No ofQUEUE. Process N, and set STATUS (N)= 3, the processed state.
Step 5. Examine each neighbor J of N
-
7/23/2019 Algorithms Question Answers Set1
8/42
a) If STATUS (J)= 1 (ready state), add Jo the rear of QUEUE and reset
STATUS (J) - 2 (waiting state).
b) If STATUS (J) = 2 (waiting state) orSTATUS (J) = 3 (processed state), ignorehe vertex J.
[End of Step 3 loop.]
Step 6.Exit.
Again, the above algorithm will process
only those vertices which are connectedo the starting vertex A.that is,he connected componentncluding A. Suppose
one wants to process all the vertices in
he graph G. Then the algorithm must bemodified so that itbegins again with another vertex (whichwe callB) that is still in the ready stateSTATUS = 1).
This vertex Bain be obtained by
-
7/23/2019 Algorithms Question Answers Set1
9/42
raversing through thelist of vertices.
EXAMPLESuppose the BFS Algorithm 8.1? B is
applied to the graph in Fig. 8-28. Thevertices are processed in the followingorder:A, D, C, B, F, E, G, HSpecifically, Figure (a)shows thesequence of waiting lists in QUEUE andhe vertices being processedAgain,
each vertex, excluding A,comes froman adjacency list and hence correspond-
to an edge of thegraph. Theseedges form a spanning tree of G whichs pictured in Figure (b).
Again,the numbersindicate theorder the ed
are added to the tree.Observe that this spanning tree isdifferent than the one inFigure (b) which came from a depth-firstsearch
-
7/23/2019 Algorithms Question Answers Set1
10/42
Depth-first Search:The generaldea behind a depth-first search
beginning at a starting
vertex A is as fellows First weprocess the starting
vertex A. Then we process each
vertex N along with a
-
7/23/2019 Algorithms Question Answers Set1
11/42
path P which begins at A;that is,
we process a neighbor of A, then
a neighbor of a neighborof A, and so on. After coming to
a "dead end", that is, to a vertex
with no unprocessed neighbor,we backtrack on the path P until
we can continue along another
path P. And so on. Thebacktracking is accomplished by
using a STACK to hold the initia
vertices of future possiblepaths. We also need a field
STATUS which tells us the
-
7/23/2019 Algorithms Question Answers Set1
12/42
current status of any vertex so
that no vertex is processed more
than once. The algorithmfollows.
Algorithm 1.12A (Depth-first Search):
This algorithm executes a depth-firstsearch on a graph G beginning with astarting vertex A.
Step 1. Initialize all vertices to the
eady state (STATUS = I)
Step 2. Push the startingvertex A onto STACK and change thestatus of A to the waiting state (STATUS= 2).
Step 3. Repeat Steps 4 and 5 untilSTACK is empty.
Step 4. Pop the top vertex N of
-
7/23/2019 Algorithms Question Answers Set1
13/42
STACK. Process N, and set STATUS (N)= 3; the processed state
Step 5. Examine
each neighbor J of N.
a) If STATUS (J)= 1(ready slate),push Jonto STACK and resetSTATUS (J) = 2 (waiting state).
b) If STATUS (J)= 2(waiting state),delete the previous J from the STACKand push the current J onto STACK
c) If STATUS (J)= 3(processed state),gnore the vertex J.
[End of Step 3 loop.]
Step 6. Exit.
The above algorithm will process onlyhose vertices which are
connected tothe starting vertex
A, thatis. the connected component
-
7/23/2019 Algorithms Question Answers Set1
14/42
ncluding A. Suppose one wants toprocess all the vertices in thegraph G.Then the algorithm must bemodified so that it begins
again withanother vertex (which wecall B) that isstill in the ready stateSTATE - 1). This vertex B can be
obtained by traversing through the list ofvertices.
EXAMPLESuppose the DFS Algorithm1.12A isapplied to the graph in fig 1-28.
The vertices are processed in thefollowing order:A, B, E, F, C, G, H, D
Specifically, Fig. (a) shows thesequenceof waiting lists in STACK and the
vertices being processed. We have usedhe slash to indicate that a vertexs deleted from the waiting list. Each
vertex, excludingA, comes froman adjacency list and hence
corresponds to an edge
-
7/23/2019 Algorithms Question Answers Set1
15/42
of thegraph. Theseedges formaspanning trof G which is pictured in Fig. (A). Thenumbers indicate the orderhat the edges arcadded to the
ree, and the dashed lines indicatebacktracking.
SATELLITE
COMMUNICATION
-
7/23/2019 Algorithms Question Answers Set1
16/42
A Geosynchronous Earth
Orbit (GEO):- This
satellite has an orbita
period that synchronizes
with the Earths speed orotation. So, for an
observer at a fixed location
on Earth, a GEO satellite
will always return to the
same place in the sky aexactly the same time each
day.
-
7/23/2019 Algorithms Question Answers Set1
17/42
It is also used in the Geo-
Stationary Earth
Orbit(GSO) satellite, it is
a special type of GEO, in
which the satellite is placedin orbit directly above the
Earths equator at a precise
height, so that it maintains
the same position relative to
the Earths surface.
Middle Earth Orbit (MEO):-Thi
satellites have orbits ranging from a few
-
7/23/2019 Algorithms Question Answers Set1
18/42
hundred miles to a few thousand mile
above the earth's surface, with orbita
periods ranging from around two to 12
hours. MEO is used mainly for satellitenavigation systems such as GPS, Galileo
Glonass and Beidu.
LOW EARTH ORBIT(LEO):-LEO
systems fly about 500 to 1,500 kilometer
above the Earth. Aypical LEO satellite takes less than two
hours to orbit the Earth,
and are only visible for 15 to 20 minute
each pass.Low earth orbiting satellitesare less expensive to launch into orbit as
distance from the earth is less, don't
equire as high signal strength and give
-
7/23/2019 Algorithms Question Answers Set1
19/42
ess time delay.
Meaning of DPCM Differentia
Pulse Code Modulation- It is amodulation technique invented by the
British Alec Reeves in 1937. It is a
digital representation of an analog signa
where the magnitude of the signal i
sampled regularly at uniform intervals
Every sample is quantized to a series o
symbols in a digital code, which iusually a binary code. PCM is used i
digital telephone systems. It is also the
standard form for digital audio i
computers and various compact discformats. DPCM allows this to be
achieved by describing only the change
between the samples.
http://www.birds-eye.net/definition/p -
7/23/2019 Algorithms Question Answers Set1
20/42
ADVANTAGES AND
DISADVANTAGES OF OSI MODEL
Advantages:-1)It provides a standard to
design networking devices by differen
vendors.
2)The protocols in OSI are much hidde
han TCP/IP and can be replaced
elatively easily as the technology
changes.
3) OSI supports both connectionless and
connection-oriented communication in the
network layer
Disadvantages:-1)Due to the complexity
of the system poor performance i
-
7/23/2019 Algorithms Question Answers Set1
21/42
obtained, especially in some real time
applications.
2) Direct substitution of layers is noalways possible e.g. if a LAN wit
broadcast capability is inserted below a
network protocol that did not support thi
facility, then this service would be lost tohe upper layers.
3) Although protecting equipment fro
becoming obsolete it simultaneouslyhinders technological advancement.
DATA TRANSMISSION
The transmission mode refers to the
number of elementary units of informatio
bits) that can be simultaneously
ranslated by the communications channel
-
7/23/2019 Algorithms Question Answers Set1
22/42
PARALLEL
CONNECTION:-
Parallel connectio
means simultaneouransmission ofNbits. These bits are sen
simultaneously overNdifferent channels.
SERIALCONNECTION: -In aserial connection, the dataare sent one bit at a time
over the transmission channel. Howeversince most processors process data iparallel, the transmitter needs toransform incoming parallel data into
serial data and the receiver needs to dohe opposite.
Asynchronous data transmission mode:
-
7/23/2019 Algorithms Question Answers Set1
23/42
n this mode, each character is sent a
rregular intervals in time. So, fo
example, imagine that a single bit i
ransmitted during a long period osilence... the receiver will not be able to
know if this i
00010000,10000000,00000100 . To
emedy this problem, each character i
preceded by some information indicatin
he start of character transmission (the
ransmission start information is calleda START bit) and ends by sending end-of
ransmission information (called STOP
bit, there may even be several STOP
bits).
ADVANTAGES: - 1)It is faster means o
connecting 2) It is Simple. 3) Doesn
equire synchronization of bot
-
7/23/2019 Algorithms Question Answers Set1
24/42
communication sides. 4)H/W cost is very
cheap.
DISADVANTAGES:-1)It is less reliable2) Large relative overhead. 3) a hig
proportion of the transmitted bits are
uniquely for control purposes and thu
carry no useful information.
Synchronous data transmission mode:
n this mode, the transmitter and receive
are paced by the same clock. The
eceiver continuously receives (eve
when no bits are transmitted) thenformation at the same rate the
ransmitter send it. This is why the
ransmitter and receiver are paced at the
same speed
-
7/23/2019 Algorithms Question Answers Set1
25/42
ADVANTAGES:- 1) supplementary
nformation is inserted to guarantee tha
here are no errors during transmission.
2) It is highly efficient. 3)Lower
overhead and thus, greater throughput 4
t is more reliable.
5)It is possible to have both sides try to
synchronize the connection at the same
ime.
DISDVANTAGES:- 1)The mai
disadvantage of synchronous transmissio
s recognising the data at the receiver.
2)It is slower than asynchronou
ransmission mode. 3)Hardware is more
expensive 4)Slightly more complex.
-
7/23/2019 Algorithms Question Answers Set1
26/42
ALOHA
ALOHA is a medium access protocol thawas originally designed for ground based
adio broadcasting however it i
applicable to any system in whic
uncoordinated users are competing for the
use of a shared channel. Pure ALOHA
and slotted ALOHA are the two version
of ALOHA.
Pure ALOHA:- Pure ALOHA uses a
very simple idea that is to let user
ransmit whenever they have data to sendPure ALOHA is featured with the
feedback property that enables it to liste
o the channel and finds out whether the
frame was destroyed. Feedback i
http://www.blurtit.com/q646302.htmlhttp://www.blurtit.com/q328653.html -
7/23/2019 Algorithms Question Answers Set1
27/42
mmediate in LANsbut there is a delay o
270 milli sec in the satellitetransmission
t requires acknowledgment if listening to
he channel is not possible due to someeason. It can provide a channe
utilization of 18 percent that is no
appealing but it gives the advantage o
ransmitting any time.
SLOTTED ALOHA:-It divides time
nto discrete intervals and each interval
corresponds to a frame of data. It requires
users to agree on slot boundaries. It does
not allow a system to transmit any time.
nstead the system has to wait for thebeginning if the next slot
Differnce b/w narrowband and
broadband communication
http://www.blurtit.com/q898327.htmlhttp://www.blurtit.com/q898327.html -
7/23/2019 Algorithms Question Answers Set1
28/42
channel:-Narrowband is associated with
dial up accounts with your ISP usually up
o speeds of 54kps but can be faster if you
use ISDN connections.
Broadband on the other hand is faster
connections up to 8mb ps and is always
online ie connected to the Internet evenwhen your PC is switched off
PAPER IX
-
7/23/2019 Algorithms Question Answers Set1
29/42
OPERATING SYSTEM
Internal fragmentation:- It occurs
when storage is allocated withoutntention to use it. This space is
wasted. While this seems foolish, it is
often accepted in return for increased
efficiency or simplicity. The terminternal" refers to the fact that the
unusable storage is inside the
allocated region but is not being used.
t is difficult to reclaim; usually the
best way to remove it is with a design
change.
External fragmentation:- It is the
phenomenon in which free storage
becomes divided into many small
pieces over time. It is a weakness of
-
7/23/2019 Algorithms Question Answers Set1
30/42
certain storage allocation algorithms,
occurring when an application
allocates and deallocates regions of
storage of varying sizes, theallocation algorithm responds by
eaving the allocated and deallocated
egions interspersed.. The term
external" refers to the fact that the
unusable storage is outside the
allocated regions.
Effects:-1)The most common side
effect of fragmentation is slowdown.
Fragmentation causes slowdown. 2)
A rather more serious side effect iswhat file fragmentation is. File
fragmentation is a direct result of
external fragmentation,occurs during
he process of data removal and
-
7/23/2019 Algorithms Question Answers Set1
31/42
expansion, another program. 3)
Another effect of fragmentation is the
program to malfunction, i.e function
slowly or do not function at all.
Solution:- The only viable solution to
fragmentation is defragmentation.
Defragmentation runs a
comprehensive scan on the hard drive
and all the files inside of it, and
determines the optimal way to storeour data. Although defragmentation
cannot solve internal fragmentation, it
will completely solve external
fragmentation.
Defragmentation is a process tha
educes the amoun
of fragmentation in file systems. It doe
http://en.wikipedia.org/wiki/File_systemhttp://en.wikipedia.org/wiki/File_system_fragmentation -
7/23/2019 Algorithms Question Answers Set1
32/42
his by physically organizing the content
of themass storage device to store files i
a contiguous region if possible, or in the
smallest possible number of regionfragments) if not. It also attempts to
create larger regions of free space usin
compaction to impede the return o
fragmentation.
Q) Why paging is used?
Ans:-Paging is used for faster access
o data. When a program needs a
page, it is available in the main
memory as the OS copies a certain
number of pages from your storage
device to main memory. Paging
allows the physical address space of
http://en.wikipedia.org/wiki/Contiguityhttp://en.wikipedia.org/wiki/Computer_filehttp://en.wikipedia.org/wiki/Mass_storage -
7/23/2019 Algorithms Question Answers Set1
33/42
a process to be noncontiguous.
Advantages of Paging:-1) Easy to
allocate physical memory 2)Easy toallocate a frame, just remove it from
ts free list 3) complication for
kernel contiguous physical memory
allocation 4) Easy to page outchunks of programs
Disadvantages of paging:- 1)
Wastage of memory space. 2)Memory reference overhead 3)
Memory required to hold page tables
hat can be large
Complete Cocomo Model:- The main
shortcoming of basic and intermediate
COCOMO model is that they consider a
-
7/23/2019 Algorithms Question Answers Set1
34/42
software product as a single
homogeneous entity. The system is made
up of sub-systems which have their own
characteristics. Sub-systems may havedifferent inherent development
complexity, reliability requirements may
be high, development team experience.
The complete COCOMO model consider
hese differences in characteristics of the
subsystems and estimates the effort and
development time as the sum of theestimates for the individual subsystems.
Q) What do you mean by S/W quality
assurance?Ans:- Software Quality Assurancenvolves the entire software developmen
PROCESS - monitoring and improvin
he process, making sure that any agreed
-
7/23/2019 Algorithms Question Answers Set1
35/42
upon standards and procedures arefollowed, and ensuring that problems arefound and dealt with. It is oriented to
prevention'.
TESTING
I) Bottom-up Testing Strategy
1)The subsystem in the lowest layer ofhe call hierarchy are tested individually
2) Then the next subsystems are testedhat call the previously tested subsystems3)This is done repeatedly until alsubsystems are included in the testin
Special program needed to do the testing,II) Top-down Testing Strategy
1) Test the top layer or the controlling
subsystem first 2) Then combine all the
-
7/23/2019 Algorithms Question Answers Set1
36/42
subsystems that are called by the tested
subsystems and test the resultin
collection of subsystems 3)Do this until
all subsystems are marked into the test4) Special program is needed to do the
esting,
Test stub : A program or a method thasimulates the activity of a missin
subsystem by answering to the callin
sequence of the calling subsystem and
eturning back fake data.
III) Sandwich Testing Strategy
1) It Combines top-down strategy wit
bottom-up strategy 2)The system is view
as having three layers A target layer in the
middle 3)A layer above the target 4) A
ayer below the target 5) Testin
-
7/23/2019 Algorithms Question Answers Set1
37/42
converges at the target layer
IV) Modified Sandwich Testing
Strategy
1)Middle layer with drivers and stubs 2
Top layer with stubs 3) Bottom laye
with drivers 4) Top layer accessing
middle layer (top layer replaces drivers)5)Bottom accessed by middle layer
V) Big-Bang Strategy:-
Big-Bang approach is very simple in itphilosophy where basically all themodules or builds are constructed andested independently of each other and
when they are finished, they are all puogether at the same time.Advantage of this approach is that it ivery quick as no drivers or stubs are
needed, thus cutting down on the
-
7/23/2019 Algorithms Question Answers Set1
38/42
Process CPU
Burst
Remainder
CPU time
Remaind
CPU time
P1 20 16 12
P2 5 1 0
P3 6 2 0
P1 P2 P3 P1 P2 P3 P
development time.Disadvantage:- 1) the least effective. 2t is very demanding on the resources 3)
There is really nothing to demonstrateuntil all the modules have been built andntegrated.
Cpu Scheduling( round robin)
Quantum = Q = 4
-
7/23/2019 Algorithms Question Answers Set1
39/42
0
4
8 12 16 17 19 3
Average waiting time: Waiting Time =
Final Start Time - Previous Time i
CPU - Arrival Time)
(19-8-0)+(16-4)+(17-4)]/3=
11+12+13)/3=12
Every one gets about the same amount o
waiting time.
S/W ENG.
SSADM:- SSADM (Structured System
Analysis & Design Method) is a widely
used computer application developmen
-
7/23/2019 Algorithms Question Answers Set1
40/42
method in the UK, where its use is ofte
specified as a requirement for governmen
computing projects. It is increasingly
being adopted by the public sector iEurope.
SSADM's objectives are to:
Improve project management &
control
Make more effective use of
experienced and inexperienced
developmentstaff
Develop better quality systems
Make projects resilient to theloss of staff
Enable projects to be supported
by computer-based tools such as
computer-aided software
-
7/23/2019 Algorithms Question Answers Set1
41/42
engineering systems
Establish a framework for good
communications between
participants in a project
SSADM STEPS:-
SSADM sets out a cascade or waterfall
view of systems development, in which
there are a series of steps, each of
which leads to the next step,
SSADM's steps, or stages, are:Feasibility
Investigation of the current
environment
Business systems optionsDefinition of requirements
Technical system options
Logical design
-
7/23/2019 Algorithms Question Answers Set1
42/42
Physical design