Wednesday, 2 September 2015

MSCIT - SEMESTER - 2 - SUMMER - 2015

PROGRAM  - Master of Science in Information Technology
SEMESTER  SECOND
SUBJECT CODE & NAME - MIT201 – OPERATING SYSTEM

1. Define operating system. Explain any four major functions of Operating system.

Operating System – Definition

Operating  System  is  a  System  Software  (Set  of  system  programs)  which provides  an  environment  to  help  the  user  to  execute  the  programs.  The Operating  System  is  a  resource  manager  which  allocates  and  manages various resources like processor(s), main memory, input/output devices and information on secondary storage devices.

Functions of Operating System

Operating systems perform the following important functions:

                                                                                     
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2. Explain the different process states.

A process is executed sequentially,  one  instruction  at  a  time.  A  program  is  a  passive  entity. Example:  a file on the disk. A process on the other hand is an active entity. In addition to program code, it includes the values of the program counter, the contents of the CPU registers, the global variables in the data section and the contents of the stack that is used for subroutine calls. In reality, the CPU switches back and forth among processes.

                                                                                     
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3.  Define Deadlock. Explain necessary conditions for deadlock.

Definition of Deadlock

Several  processes  compete  for  a  finite  set  of  resources  in  a  multiprogrammed  environment.  A  process  requests  for  resources  that  may  not be readily available at  the time of the request. In such a case the process goes into a wait state. It may so happen that this process may never change state because the requested resources are held by other processes which themselves are waiting for additional resources and hence in a wait state. This situation is called a deadlock.

                                                                                     
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4.  Differentiate  between  Sequential  access  and  Direct  access methods.

Sequential access

Sequential access increases interaction cost: the user has to inspect all the items that precede the item of interest in a list. With direct access, the user can focus on the element of interest without explicitly processing the items that come before it in the list.
Sequential access has two potential benefits:

•                                          Progressing linearly through an information space can be accomplished through particularly simple navigation controls: basically a “give me more” button.                                                                          
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5. Differentiate  between  Daisy  chain  bus  arbitration  and  Priority encoded bus arbitration.

Daisy chain arbitration:  Here, the requesting device or devices assert the signal  bus_request.  The  bus  arbiter  returns  the  bus_grant  signal,  which passes through each of the devices which can have access to the bus, as shown  in  figure 10.5.  Here,  the  priority  of  a  device  depends  solely  on  its position  in  the  daisy  chain.  If  two  or  more  devices  request  the  bus  at  the same time, the highest priority device is granted the bus first,  and then  the bus_grant  signal is                

                                                                  
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6. Explain LRU page replacement algorithm with example.

LRU page replacement algorithm

The main distinction between FIFO and optimal algorithm is that the FIFO algorithm uses the time when a page was brought into memory (looks back) whereas the optimal algorithm uses the time when a page is to be used in future (looks ahead). If the recent past is used as an approximation of the near  future, then replace the page that has not been used for the longest period of time. This is the least recently used (LRU) algorithm.

                                                                                     
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 PROGRAM  - Master of Science in Information Technology
SEMESTER - 2
SUBJECT CODE & NAME - MIT202– Data Base Management System(DBMS)

1.     What are the applications of database system

2.  Explain the functions of the following
(a)  Storage Manager
(b)  Buffer Manager

The Storage Manager: 

The Storage Manager interfaces with the operating system  (OS)  to  write  data  to  the  disk  efficiently.  Because  the  storage functions reside in a separate subsystem, the MySQL engine operates at a level of abstraction away from the operating system. This means that if you port to a different operating system that uses a different storage mechanism, for  example,  you  can  rewrite  only  the                                                            
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The  Buffer  Manager

This  subsystem  handles  all  memory  management issues  between  requests  for  data  by  the  Query  Engine  and  the  Storage Manager.  MySQL  makes  aggressive  use  of  memory  to  cache  result  sets that  can  be  returned  as-is  rather  than  making  duplicate  requests  to  the Storage Manager; this cache is                                                    
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3.  What are the important responsibilities of database manager? Explain.


The important responsibilities of database manager are as follows :

·        Interaction with file manager: The raw data is stored on the disk using the  file  system  which  is  usually  provided  by  a  conventional  operating system.  The database manager translates the various DML statements into  low-level  file  system  commands.   Thus  the  database  manager  is responsible for the actual storing, retrieving and updating of data in the database.

Integrity  enforcement:  The  data  values  stored  in  the  database  must satisfy  certain  types  of  consistency  constraints.  For  example,  the                             


                                               
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4.  Explain the Sequential File Organization.

A  sequential  file  is  designed  for  efficient  processing  of  records  in  sorted  order  based  on  some  search-key.  A  search  key  is  any  attribute  or set  of attributes; it need not be the primary key, or even a superkey. To permit fast retrieval  of  records  in  search-key  order,  we  chain  together  records  by pointers. The pointer in each record points to the next record in search-key order. Furthermore, to minimize the number of block accesses in sequential file                                                                                 
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5.  Explain basic operations of Relational algebra?

Basic  operations  are  the  traditional  set  operations:  union,  difference, intersection  and  Cartesian  product.  Three  of  these  four  basic  operationsunion, intersection, and difference  –  require that operand relations be union compatible. Two relations are union compatible if they have the same  parity and  one-to-one  correspondence  of  the  attributes  with  the                                                                
                                               
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6.  What are the disadvantages of Data Distribution.

The  primary  disadvantage  of  distributed  database  systems  is  the  added complexity  required  to  ensure  proper  coordination  among  the  sites.  This increased complexity takes the form of:

Software development cost:  It is more difficult to implement a distributed database system and, thus, more costly.

                                                                                     
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7.  Explain the following
a)  SUBSET Mapping
b)  SUPERSET Mapping

SUBSET Mapping:

This type of mapping is used when all the attributes of a persistent  class  are  mapped  to  the  same  table.  It  is  also  used  when  apersistent class is not concerned with some of the columns (not part of the business model) of its corresponding table in the database. The attributes of a persistent class with a                                                     
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SUPERSET Mapping:
This is done when a  persistent class with a superset mapping  contains  attributes  derived  from  columns  of  multiple  tables.  This type of mapping is also known as  table spanning. Superset mappings  can be used to create "view classes" that hide the underlying data model. It also can  map a class inheritance tree to the                                                     
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 PROGRAM  - MSc IT
SEMESTER  - 2
SUBJECT CODE & NAME - MIT203- ANALYSIS AND DESIGN OF ALGORITHMS

1.  Write  the  steps  involved  in  analyzing  the  efficiency  of  nonrecursive algorithms.

Analyzing efficiency of non recursive algorithms

The  steps  involved  in  analyzing  the  efficiency  of  non-recursive  algorithms are as follows:

·        Decide the input size based on the constraint n
·        Identify the basic operations of algorithm
·        Check the number of times the basic operation is executed. Find whether the execution of basic operation is dependent on input size n or not. If the basic operation is depending on worst case, best case and average case then analysis of algorithm needs more attention.
·        Set up summation  formula  for the number of times the basic operation is implemented.
·        Simplify the sum using standard formula and rules.
                                                                                 
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2. Define  selection  sort  and  explain  how  to  implement  the selection sort?

Selection  sort  is  one  of  the  simplest  and  performance  oriented  sorting techniques  that  work  well  for  small  files.  It  has  time  complexity  as  O(n2) which is unproductive on large lists.


Let us see an example for selection sort. In below figure , we use selection sort to sort                                                                                   
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3. Define Topological sort. And explain with example.  

Topological  sort  is  done  using  a  directed  acyclic  graph (DAG),  which  is  a linear ordering of all vertices G= (V, E) is an ordering of all vertices such that if  G  contains  an  edge  (u,  v),  then  u  appears  before  v  in  the  ordering.  A topological sort of a particular graph can be looked upon as a horizontal line where  all  directed  edges  travel  from  left  to  right.  Thus,  topological  sort differs  from  the  usual  sorting                                                                                    
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4. Explain  good-suffix  and  bad-character  shift  in  Boyer-Moore algorithm.

The  Boyer-Moore  algorithm  uses  two  heuristics:  good-suffix  and  badcharacter shift.

Bad character shift

We use this when mismatch occurs. We decide the number of places to shift by using bad character shift.

·        As  in  Horspool’s  algorithm  if  the  rightmost  character  does  not  match, then the pattern is shifted to the right by its length.
When  the  rightmost  character  of  the  pattern  matches  with  that  of  the text,  then each character is compared from right to left. If at some point a  mismatch  occurs  after  a  certain  number  of  ‘k’  matches  with  text’s character ‘T’, then                                            
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5. Solve the Knapsack problem using memory functions.

Item                                        1          2          3          4
Weight                                   2          6          4          8
Value (in Rs.)                         12        16        30        40
Knapsack capacity is given as W=12. Analyze the Knapsack problem using memory functions with the help of the values given above.

Answer:

If we apply the recurrence formulas to this set of data, then we will get the following table                                                                                  
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6.  Describe Variable Length Encoding and Huffman Encoding. 

Huffman codes are digital data compression codes  which  are  the outcome of  the  brilliant  piece  of  work  by  Prof.  David  A.  Huffman  (1925-1999). Huffman codes give good compression ratios. Even today,  after  50 years, Huffman codes have not only survived but  are unbeatable  in many cases. Huffman compression is a compression technique where  there  is no loss of information when the data is compressed i.e. after we  decompress the data, the  original  information  can  be  got.  Hence  it  is  named  as                                                                                       
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 PROGRAM  - Master of Science in Information Technology(MSc IT)
SEMESTER  - 2
SUBJECT CODE & NAME - MIT204– Data Communication & Networking


1.  Discuss on transmission impairments.

Transmission Impairments

Analog signal consist of varying a voltage with time  to  represent  an  information  steam.  If  the  transmission  media  were perfectly,  the  receiver  could  receive  exactly  the  same  signal  that  the transmitter  sent.  But  communication  lines  are  usually  not  perfect,  so  the receive signal is not the same as the transmitted signal. For digital data this difference  can  lead  to  errors.  Transmission  lines  suffers  from  three  major problems

1)  Attenuation distortion
2)  Delay distortion
3)  Noise

1. Attenuation distortion

It  is  the  loss  of  energy  as  the  signal  propagates  outward.  The  amount  of energy depends on the frequency. The signal attenuates as shown in below figure as it propagates. If the attenuation is too                                                                                     
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2.  Explain the major criteria for a Data Communication Network.

Criteria for a Data Communication Network

The major criteria that a Data Communication Network must meet are:

a.  Performance
b.  Consistency
c.  Reliability
d.  Recovery
e.  Security

a) Performance: Performance is the defined as the rate of transferring error free  data.  It  is  measured  by  the  Response  Time.  Response  Time  is  the elapsed  time  between  the  end  of  an  inquiry  and  the  beginning  of  a response. Request a file transfer and start the file transfer.

b)  Consistency:  Consistency  is  the  predictability  of  response  time  and accuracy  of  data.  Users  prefer  to  have  consistent  response  times,  they develop a feel for normal operating conditions. For                                                                                    
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3.  Write a note on a) 10Base2  b) 10Base- T .

a. 10Base2: Thin Ethernet

10Base2 also uses a bus topology, but the cable is much thinner and more flexible as shown in fig 7.9. The cable can be bent to pass very close to the stations.  In  this  case,  the  transceiver  is  normally  part  of  the  network interface card (NIC), which is installed inside the station.
                                                                                     
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4.  What do you mean by congestion? Explain.

Congestion

An important issue in packet switched network is congestion. Congestion in a  network  may  occur  if the  load  on  the  network  –  the  number  of  packets sent  to  the  network  0  is  greater  than  the  capacity  of  the  network  –  the number of packets a network can handle.

Congestion  happens  in  any  system  that  involves  waiting.  For  example, congestion happens on a freeway because any abnormality in the flow, such an accident in the rush hour, creates blockage.

Congestion  in  a  network  or  internetwork  occurs  because  routers  and switches  having  queues,  buffers  that  hold  packets  before  and  after processing.  A  router,  for  example,  has  an  input  queue                                                                                     
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5.  Explain the following
a)  Class A networks
b)  Class B networks


a. Class A networks

Each Class A network address has an 8-bit network-prefix with the highest order bit set to 0 and a seven-bit network number, followed by a 24-bit hostnumber.  Today,  it  is  no  longer  considered  'modern'  to  refer  to  a  Class  A network. Class A networks are now referred to as "/8s" (pronounced "slash eight" or just "eights") since they have an 8-bit network-prefix. A maximum of 126 (2 7-2) /8 networks can be defined as shown in figure 2.1(b).  The  calculation  requires  that  the  2  is  subtracted  because  the  /8
network 0.0.0.0 is reserved for use as the default route and the /8 network 127.0.0.0 (also written 127/8        


                                                                            
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b. Class B networks

Each  Class  B  network  address  has  a  16-bit  network-prefix  with  the  two highest  order  bits  set  to  1-0  and  a  14-bit  network  number,  followed  by  a 16-bit host-number as illustrated in figure 2.1(b). Class B networks are now referred to as"/16s" since they have a 16-bit network-prefix. A maximum of 16,384 (2 14 ) /16 networks can be defined with up to 65,534 (2 16-2) hosts per network. Since the entire                                                      
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6.  Explain the following.         
a)  Open loop congestion control
b)  Closed loop congestion control

a)  Open loop congestion control


In  this  mechanism,  policies  are  applied  to  prevent  congestion  before  it happens. In these mechanisms, congestion control is handled either by the source or the destination.

Retransmission  policy:  Retransmission  is  sometimes  unavoidable.  If  the sender feels that a sent packet is lost or corrupted, the packet needs to be etransmitted.  A  good  retransmission  policy  can  prevent  congestion.  The retransmission  policy  and  retransmission  timers  must  be  designed  to optimize efficiency and at the same time prevent congestion.

                                                                                     
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b)  Closed loop congestion control

These  mechanisms  try  to  alleviate  congestion  after  it  happens.  Several mechanisms have been used by different protocols. We describe only a few of them.

i) Backpressure:  This technique refers to a congestion control mechanism in  which  a  congestion  node  stops  receiving  data  from  the  immediate upstream node or nodes. This may cause the upstream node or nodes to become congested, and they, in turn, reject data from their upstream node or  nodes.  And  so  on.  Backpressure  is  a  node-to-node  congestion  control that starts with a node and propagates, in the opposite direction of data flow, to  the  source.  The  backpressure  technique  can  be  applied  to                                                    
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7.  Explain the categories Network security problems.

Network security problems can be divided roughly into four categories:

1)  Secrecy:  It  is  also  called  confidentially.  It  has  to  do  with  keeping information out of hands of unauthorised users.

2)  Authentication:  It  deals  with  determining  who  the  destination  or recipient  is  before  revealing  sensitive  information  or  entering  into  a business deal.

                                                                                     
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