Microsoft Software

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Microsoft Software

• Lecturer Jing Liu
• Email neouma_at_mail.xidian.edu.cn
• Homepage http//see.xidian.edu.cn/faculty/liujing
  

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Microsoft Software

• Personal computers are becoming increasingly
  powerful, versatile and popular among
  organizations and individuals alike not because
  of reduction in their cost and increase in memory
  size but primarily due to the tremendous power
  and variety of software available.
• In fact, it is the software that makes a computer
  useful as well as user-friendly. Although there
  are a number of software vendors in the market,
  the main driving force behind the software
  revolution is the Microsoft Corporation.

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Microsoft Software

• The first major software project of Microsoft
  Corporation was the development of an operating
  system known as Disk Operation Systems (DOS) for
  the original IBM personal computer in the year
  1980.
• Although originally seen as a supplier of
  operating systems, Microsoft went on to develop a
  variety of successful application packages, thus
  becoming a leading software company in the world.
  Microsoft today has a suite of software packages
  that would meet many of the standard applications
  requirements of most organizations. This software
  suite, popularly known as Microsoft Office,
  includes the following application packages

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Microsoft Software

• Microsoft Word Developed in 1983, it provides
  powerful tools for creating and manipulating word
  processing documents.
• Microsoft Excel Developed in 1985, it enables to
  create detailed spreadsheets for viewing and
  collaboration.
• Microsoft PowerPoint Developed in 1988, it
  provides a complete set of tools for creating
  presentations.
• Microsoft Publisher Developed in 1991, it helps
  in publishing materials, such as news letters,
  brochures and catalogs
• Microsoft Access Developed in 1912, it gives
  powerful tools for creating and managing
  databases.

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MS Word System

• MS Word is an application software that can be
  used to create, edit, save and print personal as
  well as professional documents in a very simple
  and efficient manner. It is mainly designed for
  word processing, so it is also referred as the
  word processing program.
• MS Word is not the only word processing program
  available in the market. There are many other
  word processing applications available, such as
  Open Office Writer and Google Docs.
• For working in MS Word, we need to install MS
  Office in a computer system. After installing MS
  Office, we can start MS Word using Start menu.

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MS Word System

• Major components on the GUI of MS Word
• Title bar It is a horizontal bar at the top of
  the window that displays the name of the
  currently opened MS Word document. By default, MS
  Word assigns names to new documents as Document1,
  Document2, Document3 and so on. However, we can
  also save our document with some other name of
  our choice.
• Menu bar It is located right below the title
  bar. The Menu bar is used to house a set of
  commands that can be used to perform various
  operations such as opening a file, closing a file
  and creating a table.
• Toolbar It is located right below the menu bar.
  A number of toolbars are provided in MS Word for
  a quick and easy access to the various commands
  housed in the Menu bar.

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MS Word System

• Document window It is the actual area in the MS
  Word window where we can enter text and draw
  graphics. The document windows of MS Word can
  also be considered as a text editor because you
  can edit and apply different types of formatting
  to the text in this window.
• Status bar It is located at the bottom of the MS
  Word window. The status bar provides some helpful
  information related to the document that we are
  currently working with. The information provided
  by the status bar includes
• Total number of pages in the document
• Page number of the active page
• Line number of the line of text where the cursor
  is currently positioned
• Column number of the character in the line of
  text where the cursor is currently positioned
• Status of various modes such as track mode,
  extend selection mode and overtype mode

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MS Word System

• Scroll bar The term scroll bar usually refers to
  the horizontal and the vertical bars placed at
  the right and the bottom of the MS Word windows.
  These bars allow the user to view those portions
  of the document that cannot fit on the screen at
  one time.
• Ruler It is located below the toolbars. The
  ruler bar in MS Word is used to set the alignment
  for the content in the document. If the ruler bar
  is not displayed in the MS Word window, then we
  can make it visible by selecting View-gtRuler.

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MS Word System - Menu Bar

• File menu It contains a set of commands that can
  be used to perform various file handling
  operations. The file handling operations in MS
  Word are usually known as document handling
  operations. The various operations that can be
  performed using the options available in the File
  menu are opening a new document, opening an
  existing document, saving the current document,
  printing the current document, etc.
• Edit menu It contains a set of commands that
  can be used to perform various operations related
  to content editing and manipulation. The various
  operations that we can perform using the options
  available in the Edit menu are copying the
  currently selected text to clipboard, moving the
  currently selected text to some other location in
  the currently opened document, pasting the text
  from clipborad to the currently opened document,
  deleting the selectee text, tec.
• View menu It contains a set of commands that can
  be used to display the document in different
  views. The different views available in MS Word
  are Normal, Web Layout, Print Layout, Document
  Map, Full Screen and Zoom. Apart from changing
  the view of a document , we can also perform
  various other tasks using the View menu like
  displaying or hiding the toolbar, setting the
  header and footer for a document and displaying
  or hiding the rulers.

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MS Word System - Menu Bar

• Insert menu It contains a set of commands that
  can be used to insert various objects such as
  clip art, auto shapes, organization chart, word
  art and text box in a document to make it more
  attractive. Apart from these objects we can also
  insert date and time, page numbers, symbols, page
  break and column break in the document.
• Format menu It contains a set of commands that
  can be used to alter the look and layout of the
  content present in the document. The various
  tasks that can be performed using the options
  available in the Format menu are changing the
  font type, font color, font size and font style
  of the selected text, indenting a paragraph,
  inserting bullets and numbering in the document,
  etc.
• Tools menu It contains a set of commands that
  can be used to perform advanced operations in the
  MS Word document. The various tasks that can be
  performed using the options available in the
  Tools menu are checking and correcting spelling
  and grammatical mistakes, counting the number of
  words and characters, protecting a document and
  using mail merge, etc.

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MS Word System - Menu Bar

• Table menu It contains a set of commands that
  can be used to perform various operations related
  to the creation , modification and deletion of
  tables in a document.
• Windows menu It contains a set of commands that
  can be used to perform various tasks related to
  the active windows in which we are working. Using
  his menu, we can open a new window containing the
  same content as the active window, split the
  active window into different panes and arrange
  all the opened document into separate windows in
  such a manner hat all the windows can be viewed
  at the same time by the user.
• Help menu It assists the user by providing
  information related to MS Word from various
  sources such as Office Assistant tool and
  Microsoft Office Web site etc.

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MS Word System - Toolbar

• The three most commonly used toolbars in MS Word
  are as follows
• Standard toolbar It provides quick access to the
  various operations related to the file handling
  and content editing and manipulation. If the
  Standard toolbar is not visible in the MS Word
  window, then we need to select View-gt Toolbars
  -gt Standard to make it visible.
• Formatting toolbar It is used to perform various
  operations related to the look and the layout of
  the document content. Using the icons available
  on this toolbar, we can change the font size,
  style and color of the selected text, align the
  selected text to the left, center or right of the
  screen, create numbered and bulleted list, etc.
  If the Formatting toolbar is not visible in the
  MS Word window, then we need to select View -gt
  Toolbars -gt Formatting to make it visible.
• Drawing toolbar It is located at the bottom of
  the screen just above the status bar. Using the
  different icons available on the drawing
  toolbar, we can draw and manipulate different
  types of graphics in a document. The various
  shapes that we can draw using the drawing toolbar
  are line, rectangle, oval, etc. We can also
  insert clip art, word art and pictures in the
  document using this toolbar. If the Drawing
  toolbar is not visible in the MS Word window,
  then we need to select View -gt Toolbars -gt
  Drawing to make it visible.

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MS Word System

• The following are the key operations that we can
  perform in MS Word
• Creating a document
• Saving a document
• Editing a document
• Formatting a document
• Printing a document

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MS Excel System

• MS Excel is an application program that allows us
  to create spreadsheets, which are represented in
  the form of a table containing rows and columns.
• The horizontal sequence in which the data is
  stored is referred to as a row. The vertical
  sequence in which the data is stored is referred
  to as a column.
• Each value in a spreadsheet is stored in a cell,
  which is the intersection of rows and columns.
• A cell can contain either numeric value or a
  character string.

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MS Excel System

• Worksheet is the actual working area consisting
  of rows and columns. The worksheets are also
  known as the spreadsheets. A work book in MS
  Excel is a combination of several worksheets.
  Each workbook of MS Excel contains three
  worksheets by default. The key operations that
  are performed in MS Excel include
• Creating a worksheet
• Saving a worksheet
• Modifying a worksheet
• Renaming a worksheet
• Deleting a worksheet
• Moving a worksheet
• Editing a worksheet

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MS PowerPoint System

• MS PowerPoint is a software application included
  in the MS Office package that allows us to create
  presentations. PowerPoint provides a GUI with the
  help of which we can create attractive
  presentations quickly and easily.
• The presentation may include slides, handouts,
  notes, outlines, graphics and animations. A slide
  in PowerPoint is a combination of images, text,
  graphics, charts, etc. that is used to convey
  some meaning information.
• The presentations in MS PowerPoint are usually
  saved with the extension .ppt. The interface of
  MS PowerPoint is similar to the other interfaces
  of MS Office applications.
• PowerPoint presentations are commonly used in
  business, schools, colleges, training programs,
  etc.

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MS PowerPoint System

• The following are the key operations that can be
  performed in MS PowerPoint
• Creating a new presentation
• Designing the presentation
• Saving a new presentation
• Adding slides to the presentation
• Printing the presentation

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Data Communications and Networks
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Introduction

• Computers were originally developed as
  standalone, single-user systems. Stand-alone
  computers can receive users data, manipulate
  them and provide useful information for making
  decisions. Here, the user uses his own data for
  his own decision making purposes. When the use of
  computers spread across government offices and
  business organizations, a number of issues were
  raised.
• What if a user wants to share his computer
  generated information with other colleagues?
• What if a user want s to explore the possibility
  of using certain information stored else where?
• Theses issues were addressed by the subsequent
  developments in software, hardware and
  communication technologies which have enabled the
  computers to communicate between each other and
  exchange information quickly and accurately and
  at any time.

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Introduction

• The process of electronic transfer of information
  between two locations is known as data
  communication. The five basic elements of data
  communication are
• Message It is the information to be
  communicated. It may be in the form of text,
  pictures, audio, video, or any combination of
  these.
• Sender It is the device that creates and
  transmits the information.
• Receiver It is the device that receives the
  information.
• Medium It is the communication channel through
  which the information travels from sender to
  receiver. It could be a physical wire or radio
  waves.
• Protocol It represents a set of rules that
  governs the communication process between the
  sender and the receiver.
• Data communication may occur in a simple
  point-to-point mode or in a multipoint mode where
  more than two computers are connected together in
  the form of a network. A network is a system of
  interconnected computers that can communicate
  with one another to share applications and data.

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Computer Network

• Computer network is a system of interconnected
  computers that enable the computers to
  communicate with each other and share their
  resources, data and application.
• The physical location of each computer is
  tailored to personal and organizational needs. A
  network may include only personal computers or a
  mix of PCs, minis and mainframes spanning a
  particular geographical area.
• Computer networks that are commonly used today
  may be classified as follows

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Computer Network

• Based on geographical area
• Local Area Networks (LANs)
• Wide Area Networks (WANs)
• Metropolitan Area Networks (MANs)
• International Network (Internet)
• Intranet

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Computer Network

• Based on how computer nodes are used
• Client Server Networks (CSNs)
• Peer-to-Peer Networks (PPNs)
• Valued-added Networks (VANs)

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Local Area Network (LAN)

• LAN is a group of computers that are connected in
  a small area such as building, home, etc.
• Through this type of network, users can easily
  communicate with each other by sending and
  receiving messages.
• Though the number of computers connected in a LAN
  is limited, the data is transferred at an
  extremely faster rate.

LAN
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Wide Area Network (WAN)

• WAN is a group of computers that are connected in
  a large area such as continent, country, etc. WAN
  is generally used for connecting two or more LANs
  through some medium such as leased telephone
  lines, microwaves, etc. In WAN, data is
  transferred at slow rate.

LAN
LAN
WAN
LAN
LAN
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Metropolitan Area Network (MAN)

• MAN is a network of computers that covers a large
  area like a city. The size of the MAN generally
  lies between that of LAN and WAN, typically
  covering a distance of 5Km to 50 Km.
• The geographical area covered by MAN is
  comparatively larger than LAN but smaller than
  WAN. MAN is generally owned by private
  organizations.
• MAN is generally connected with the help of
  optical fibres, copper wires etc. One of the most
  common example of MAN is cable television network
  within a city. A network device known as router
  is used to connect the LANs together. The router
  directs the information packets to the desired
  destination.

LAN
LAN
LAN
LAN
LAN
LAN
Cable television network
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The Internet

• The Internet is a global area network that allows
  computers connected over the network to share
  resources and information using different
  protocols. It is basically a network of networks
  across the globe.
• Users at different locations can very easily
  communicate with each other via the Internet. The
  Internet basically uses a set of protocols such
  as Transmission Control Protocol/Internet
  Protocol (TCP/IP) for transferring the data over
  the network. The following are the different
  types of services provided by the Internet to the
  users
• E-mail
• Online chat
• Online shopping

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The Internet

• There are various advantages of using the
  Internet
• Information The Internet allows users to access
  large amount of information efficiently.
• Availability The Internet is available
  continuously to the users all the time without
  any delay. Users can access the information from
  the Internet at any time.
• Cost The Internet provides different facilities
  to the users at a low cost. Users can access any
  website over the Internet absolutely free. The
  cost of sending messages through e-mail is also
  cheaper as compared to postal messages.

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The Internet

• The following are some of the disadvantages of
  using the Internet
• Hacking The process of illegally accessing the
  personal information stored over the Internet is
  called hacking.
• Virus The software program that itself gets
  activated in our computer system and destroys the
  stored information is called virus. Virus usually
  corrupts the resources that are connected over
  the Internet.
• Bulk e-mail It is the most common problem of the
  Internet where the unwanted bulk messages such as
  subscription mails, advertisement mails, job
  alert mails etc. are received on the users
  account. These messages are sometimes frustrating
  and irritating for the users because the user
  simply does not require these mails.

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The Intranet

• Intranet is a private network, which is confined
  at a single organization only. This type of
  computer network allows only the internal users
  of the organization to share the resources.
  However, the users outside the organization can
  also access the Intranet but they can do so only
  if they are authorized.
• The concept of Intranet was used for sharing the
  companys information amongst the employees.
  Certain protocols such as TCP/IP, HTTP, etc. are
  used by Intranet for enabling the communication
  between the computer systems.
• The website of the Intranet is provided with the
  firewall, which is a layer that helps in ensuring
  the security of the information and resources.
• The only disadvantage of Intranet is that it is
  relatively insecure as compared to the other
  networks.

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The Intranet

• The various advantages of using Intranet are as
  follows
• It allows the employees of an organization to
  access the organizations information easily and
  quickly
• Intranet users can easily communicate with each
  other within the organization
• It is relatively easier to maintain and implement
  Intranet than the Internet

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Client Server Network (CSN)

• CSN basically consists of two computers, client
  computer and server computer. The client
  computers are dummy computers, which simply send
  requests to the server computer, whereas the
  server computers receive and execute the requests
  sent by the client computer.
• CSN is also known as the client server
  architecture. This architecture is a two-tier
  architecture, which is divided into two layers.
  The first layer comprises of the user interface
  that is located on the clients desktop. On the
  other hand, the second layer is the database
  management layer, which is located on the server
  machine so as to provide services to the clients.
• In CSN, a client computer sends a request related
  to processing of data to the server. The server
  receives the request from the client computer and
  processes the data. It then sends the output
  obtained after the processing of data to the
  client computer as a response to its request.

Client
Client
Server
Client
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Peer-to-peer Network (PPN)

• In PPN, there is no separate division as clients
  and servers. Every computer in the PPN is treated
  equally and can send as well as receive the
  messages directly.
• PPN architecture cannot work under heavy load.
  This type of architecture is commonly used for
  file sharing and chatting in real time.
• Computers connected in this network can easily
  share their resources with the other computers.
  PPN is used in a variety of fields such as
  business, education, telecommunications, military
  etc.

Peer5
Peer1
Peer4
Peer2
Peer3
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Network Topologies

• Network topology refers to the arrangement of
  computers connected in a network through some
  physical medium such as cable, optical fibre etc.
  Topology generally determines the shape of the
  network and the communication path between the
  various computers (nodes) of the network. The
  various types of network topologies are as
  follows
• Hierarchical topology
• Bus topology
• Star topology
• Ring topology
• Mesh topology
• Hybrid topology

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Hierarchical Topology

• The hierarchical topology is also known as tree
  topology, which is divided into different levels.
  
• This type of topology is arranged in the form of
  a tree structure in which top level contains
  parent node (root node), which is connected with
  the child nodes in the second level of hierarchy
  with the point-to-point link.
• The second level nodes are connected to the third
  level nodes, which in turn are connected to the
  fourth level nodes and so on.
• Except the top-level node, each level node has a
  parent node.

Top level
Second level
Third level
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Linear Bus Topology

• In the linear bus topology, all the nodes are
  connected to the single backbone or bus with some
  medium.
• When a node wants to communicate with the other
  nodes in the network, it simply sends a message
  to the common bus. All the nodes in the network
  then receive the message but the nodes for which
  it was actually sent only processes it. The other
  nodes discard the message.

Cable end
Cable end
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Star Topology

• In the star topology, all the nodes are connected
  to a common device known as hub.
• When a node wants to send a message to the other
  nodes, it first sends the message to the hub,
  which in turn forwards the message to the
  intended node.
• Each node in the network is connected with a
  point-to-point line to the centralized hub. The
  task of hub is to detect the faulty node present
  in the network. On the other hand, it also
  manages the overall data transmission in the
  network.

Hub
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Ring Topology

• In the ring topology, the nodes are connected in
  the form of a ring. Each node is connected
  directly to the other two nodes in the network.
• The node, which want s to send a message, first
  passes the message to its consecutive node in the
  network.
• Data is transmitted in the clock wise direction
  form one node to another.
• Each node incorporates a repeater, which passes
  the message to next node when the message is
  intended for another node.

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Mesh Topology

• In mesh topology, each computer is connected to
  every other computer in point-to-point mode.
• For example, if we have four computers, we must
  have six links. If we have n computers, we must
  have n(n-1)/2 links.
• A message can take several possible paths to
  reach a destination.

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Hybrid Topology

• The hybrid topology is the combination of
  multiple topologies, used for constructing a
  single large topology.
• The hybrid topology is created when two different
  network topologies are interconnected. If two
  ring topologies are connected then the resultant
  topology is not the hybrid topology.
• On the other hand, if the ring topology is
  connected to the bus topology then the resulting
  topology is called the hybrid topology. This
  topology generally combines the features of the
  two topologies and is therefore more effective
  and efficient than the individual topologies.

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Network Media

• Network media refers to the physical media used
  to connect the computer nodes together. There are
  many types of transmission media, the most
  popular ones are
• Cables Some of the commonly used cables are
  telephone lines, twisted-pair cables, coaxial
  cables. Cable is one of the easiest methods of
  transferring messages from one place to another.
• Optical fibre A thin strand of glass that
  transmits pulsating beams of light rather than
  electric current. These light pulses carry
  information. Fibre-optic cables can thus carry
  information in digital form. They can carry
  enormous amount of messages at extremely fast
  speed. These are used for long distance
  communications. It is a highly secured
  transmission medium.

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Network Media

• Microwave communication through microwave can be
  used when the transmitting and receiving ends are
  located at a large distance from one another.
  Microwaves are used to transmit analogy signals.
  WANs often use microwave links to connect LANs
  together. This mode of transmission is greatly
  affected by the weather conditions.
• Satellite Satellites are used for receiving and
  transmitting analog signals globally. We can send
  data from one country to another with the help of
  satellites. WANs that cover long distances often
  use satellites for linking LANs.

43
Network Protocol

• In order to share data between computers, it is
  essential to have appropriate network protocols
  and software. With the help of network protocol,
  computers can easily communicate with each other
  and can share data, resources etc.
• Network protocols are the set of rules and
  regulations that are generally used for
  communication between two networks.
• Any two networks communicate with each other by
  sending and receiving messages in the form of
  packets. The techniques that is used separating a
  message into packets is called packet switching.
• Each packet contains the address of the computer
  from which the message was sent and also of the
  computer, which will receive the message. In
  order to send the packet, routers and switches
  are connected over the network path that
  forwards, the packet to the intended receiver.

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Network Protocol

• Using network protocol, the following tasks can
  be performed
• Identification of the type of the physical
  connection used
• Error detection and correction of the improper
  message
• Initiation and termination of the communication
  session
• Message formatting
• Some of the commonly used network protocols are
  Hyper Text Transfer protocol (HTTP), Simple Mail
  Transfer Protocol (SMTP), File Transfer Protocol
  (FTP), Transmission Control Protocol/Internet
  Protocol (TCP/IP), Telecommunications Network
  (Telnet), Domain Name System (DNS) etc.

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Network Software

• Network software refers to the set of
  instructions that are given to the computers
  connected in a network to perform different
  tasks. These instructions are given in the form
  of a program, which is usually written in some
  programming language such as C, Java, C etc.
• The network software generally provides support
  to the computers connected in a network so that
  they can communicate with each other by
  exchanging information.
• Network operating system software is the type of
  network software that basically controls the
  network traffic, access to the network resources
  such as printers, files, etc. This type of
  software generally provides multiuser,
  multitasking facilities so as to ensure effective
  communication between the computers over the
  network. It also establishes the communication
  between multiple computers that are performing a
  single task.

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Applications of Network

• Network is the system of computers generally
  linked together to enable the flow of data
  between the interconnected computers. With the
  help of network, we can access the data remotely.
  Some of the applications of a network are
• Data sharing In order to share the data among
  multiple users, it is generally stored on the
  servers. Different applications can therefore
  access the data from these servers easily.
• Remote data access Remote data access is the
  process of accessing the data from remote
  location in an efficient way. Different software
  programs are used to provide an interface to the
  end users for accessing the data remotely.

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Applications of Network

• Resource sharing It is the process of sharing
  the resources such as storage devices,
  input/output devices, etc. over the network. For
  example, printer can be shared among the
  computers connected in a network by attaching it
  to the server computer. When the users want their
  documents to be printed they can simply give the
  print command from there computers and get their
  document printed. The sharing of a printer on a
  network is relatively cheaper than attaching
  separate printers to the individual computer
  connected in the network.
• Personal communication The far-reaching
  applications of networks are electronic mail and
  teleconferencing. These applications allow
  individuals as well as organizations to use
  networks for exchanging messages (written, voice
  and video) extensively. Emails enables a person
  to send and receive instant messages over a
  computer network with the help of Internet. On
  the other hand, teleconferencing enables
  real-time communication over a distance by
  allowing people at different locations to
  communicate with each other by seeing the video
  picture of people at other sites.

48
The Internet and World Wide Web
49
The Internet and World Wide Web

• Internet is a popular buzzword among many people
  today. Almost everyone working in government
  offices and business organizations is using the
  Internet for exchange of information in one form
  or the other.
• World Wide Web is another popular phrase among
  the computer users. It is commonly referred to as
  the Web. Most people consider the Internet and
  the World Wide Web to be synonymous, but they are
  not. Although these two terms are used
  interchangeably, they actually describe two
  different but related things.

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The Internet and World Wide Web

• The Internet is a massive network of networks
  that links together thousands of independent
  networks thus bringing millions of computers on a
  single network to provide a global communication
  system. It acts as a facilitator for exchange of
  information between computers that are connected
  to the Internet. It is like a network of roads in
  a country that facilitates the movement of
  vehicles around the country.
• We can create special documents known as
  hypertext documents containing text, graphics,
  sounds and video on a computer. The storage
  location of these documents is known as website.
  The World Wide Web is the network of all such
  websites all around the world. It is popularly
  known as WWW or Web. The websites are spread
  across the Internet and therefore, the
  information contained in the websites can be
  transmitted through the Internet. It is like
  transporting the goods stored in the warehouses
  using the road network. So the Web is just a
  portion on the Internet and not same as the
  Internet.

51
Understanding the World Wide Web

• WWW is a collection of web servers, which contain
  several web pages pertaining to different
  websites. The web pages contain hypertext, simple
  text, images, videos and graphics. The web pages
  are designed with the help of HyperText Markup
  Language (HTML).
• To view the web pages provided by a web server,
  the software known as web browser is required. To
  display the web pages, a web browser runs the
  HTML code segment written for a particular web
  page. Each web page on the Internet is provided
  its own address known as Uniform Resource
  Identifier (URI or URL).
• This URL helps the web browser in locating a web
  page on the Internet. A URL string begins with
  the name of a protocol such as http or ftp that
  represents the protocol through which a web page
  is accessed. The rest of the URL string contains
  the domain server name of the web page being
  accessed and the location of the web page on the
  local web server.

52
Web Browsers

• Web browser is the software, which is used to
  access the Internet and the WWW. It is basically
  used to access and view the web pages of the
  various websites available on the Internet. A web
  browser provides many advanced features that help
  achieve easy access to the Internet and WWW.
• When we open a web browser, the first page, which
  appears in the web browser window, is the home
  page set of that particular web browser.
• The most commonly used web browsers are Internet
  Explorer (IE), Netscape Navigator and Mozilla
  Firefox.

53
Protocols Used for the Internet

• Each computer on a network has a unique address,
  which is known as the Internet Protocol (IP)
  address.
• An IP address is a group of four numbers and the
  numbers are separated from each other by a dot.
  When any data is sent from one computer to
  another computer over the network, it is divided
  into small modules known as packets or datagrams.
  These packets are transmitted on the network by
  the Internet Protocol.
• Each packet transmitted on the network contains
  the addresses of both source and destination
  computer. A gateway present on the network reads
  the address of the destination computer and sends
  the data to the specified address. Gateway is a
  computer, which contains the software required
  for the transmission of data over different
  networks.

54
Protocols Used for the Internet

• Each packet on the network is an independent
  entity, so they are transferred through different
  routes to reach the destination computer.
• The packets received at the destination are not
  in the same sequence in which they were
  transmitted. As a result, these packets are
  arranged in a right sequence by a protocol known
  as TCP and then are merged at the destination to
  form the complete data.
• TCP and IP work in coordination with other
  protocols such as Telnet and User Datagram
  Protocol (UDP) but are considered as the most
  fundamental of all protocols. All these protocols
  are collectively known as TCP/IP suite.
• A model known as TCP/IP model determines how the
  protocols of the TCP/IP suite will work together
  for the transfer of data between computers in a
  network.

55
TCP/IP Model

• The TCP/IP model was initially developed by US
  Defence Advanced Research Projects Agency
  (DARPA). This model is also known as the Internet
  Reference model or DoD model. It consists of four
  layers, namely application layer, transport
  layer, network layer, and physical layer.
• The physical layer in the TCP/IP model is
  responsible for interacting with the medium of
  transmission of data, whereas the application
  layer helps in interacting with the users. The
  four layers of TCP/IP and the functions performed
  by the these layers are as follows

Application Layer
Transport Layer
Network Layer
Physical Layer
56
TCP/IP Model

• Application layer It is responsible for managing
  all the user interface requirements. Many of the
  protocols, such as telnet, FTP, SMTP, DNS, NFS,
  LPD, and DHCP work on this layers.
• Transport layer It is responsible for the
  delivery of packets or datagrams. It also hides
  the packet routing details form the upper layer,
  i.e. the application layer. In addition, the
  transport layer allows detection and correction
  of errors and helps to achieve end-to-end
  communication between devices. The transport
  layer connects the application layer to the
  network layer through two protocols , namely TCP
  and UDP.

57
TCP/IP Model

• Network layer It contains three protocols that
  perform different functions
• Internet Protocol (IP) IP is a connectionless
  protocol that is responsible for the delivery of
  packets. The IP protocol contains all the address
  and control information for each transmitted
  packet.
• Internet Control Message Protocol (ICMP) It is
  responsible for reporting errors, sending error
  messages and controlling the flow of packets. It
  is more reliable than the IP as it is capable of
  determining errors during data transmission
• Address Resolution Protocol (ARP) It is
  responsible for determining the Media Access
  Control (MAC) address corresponding to an IP
  address. It sends an ARP request on the network
  for a particular IP address and the device, which
  identifies the IP address as its own, returns and
  APR reply along with its MAC address.

58
TCP/IP Model

• Physical layer It is responsible for collecting
  packets so that the frames, which are transmitted
  on the network, can be formed. It performs all
  the functions required to transmit the data on
  the network and determining the ways for
  accessing the medium through which data will be
  transmitted. This layer does not contain any
  protocols but instead of protocols, it contains
  some standards such as RS-232C, V.35 and IEEE
  802.3.