ELE 203

• Computer network


  Two or more autonomous computers that are linked (connected) together
• Purposes of a computer network

  • Share resources (files, printers, modems, fax machines)
  • Share Application software like MS Office
  • Allow Electronic communication
  • Increase productivity (makes it easier to share data amongst users)
• Transmission media


  Cables, telephones lines, radio waves, satellites
• Components of a computer network

  • Network operating system in the client and server machines
  • Cables which connect different computers
  • Supporting hardware in between such as bridges, routers and switches
  • In wireless systems, antennas and towers
• Network goals and motivations

  • Cost reduction by sharing hardware and software resources
  • Provide high reliability by having multiple sources of supply
  • Provide an efficient means of transport for large volumes of data among various locations (High throughput)
  • Provide inter-process communication among users and processors
  • Reduction in daily driving data transport
  • Increase productivity by making it easier to share data amongst users
  • Repairs, upgrades, expansions, and changes to the network should be performed with minimal impact on the majority of network users
  • Standards and protocols should be supported to allow many types of equipment from different vendors to share the network (Inter-operatability)
  • Provide centralised/distributed management and allocation of network resources like host processors, transmission facilities etc.
• Basis for classification of computer networks

  • Transmission media used (wired, wireless)
  • Transmission technology (point-to-point, broadcast)
  • Geographical area of coverage (LAN, WAN, MAN)
  • Management method (peer-to-peer, client/server)
  • Topology (bus, star, ring)
  • Set of rules enforced (protocols)
• Client/Server architecture


  The client (personal computer or workstation) is the requesting machine and the server is the supplying machine, both connected via a LAN or WAN

  
• Client/Server architecture


  • The client contains the user interface and may perform some or all of the application processing
  • Servers can be high-speed microcomputers, minicomputers or even mainframes
  • A database server maintains the databases and processes requests from the client
  • An application server provides additional business processing for the clients
• Peer-to-Peer architecture


  Each workstation has equal capabilities and responsibilities, acting as both a client and a server
• Peer-to-Peer architecture


  • No central repository for information and no central server to maintain
  • Data and resources are distributed throughout the network
  • Each user is responsible for sharing data and resources connected to their system
  • Generally simpler and less expensive, but usually do not offer the same performance under heavy loads
• Local Area Network (LAN)


  A computer network designed for an organization or business outfit, covering a short distance, typically implemented in a room, a floor or a building
• Characteristics of LAN


  • Limited by number of computers and distance covered
  • Usually one kind of technology is used throughout the network
  • Put up to service a department within an organization
• Metropolitan Area Network (MAN)


  A computer network designed for a town or city, larger than a LAN but smaller than a WAN
• Characteristics of MAN


  • Confined to a larger area than a LAN and can range from 10km to a few 100km in length
  • Slower than a LAN but faster than a WAN
  • Operates at a speed of 1.5 to 150 Mbps
  • Expensive equipment
  • Moderate error rates
• Wide Area Network (WAN)


  A computer network that spans a relatively large geographical area, typically connecting two or more LANs
• Characteristics of WAN


  • Can range from 100km to 1000km and the speed between cities can vary from l.5 Mbps to 2.4 Gbps
  • Supports large number of computers and multiple host machines
  • Various segments of network are interconnected using sophisticated support devices like routers and gateways
  • Usually the speed is much slower than LAN speed
  • Highest possible error rate compared to LAN and MAN
• ICT


  Information and Communications Technology
• ICT covers


  • All forms of Computer and Communications equipment
  • Software used to create, store, transmit, receive, interpret, and manipulate information in its various formats
• Hardware


  The physical parts of the system that one can see and touch e.g. CPU, computer's display or monitor etc.
• Software


  Helps create and manipulate information such as text, data, picture or video
• Types of software


  • Operating system (OS) software
  • Application software
• Operating system software


  Vital and a must on computer system without which it will not function e.g. Windows OS, Mac etc.
• Application software


  Required for function enabling and communication with other devices e.g. Microsoft Office, Adobe, drivers etc.
• ICT literacy


  Begins with computer literacy, the knowledge and use of Computers
• Computers can be found in a lot of places apart from individual homes, such as workplaces, schools, libraries and businesses
• A variety of tasks are done at a fraction of the time unlike before
• Skills required to be ICT literate

  • Understand and be able to use a computer
  • Have some basic typing skills
  • Ability to identify various ICT technologies and their uses
  • Be able to decide which ICT technology is suitable for a particular task
  • Ability to differentiate between various forms of information and understand how to use or manipulate them
• Ways to acquire ICT skills

  • Register for Computer training classes
  • Register for an online or internet training course (tutorials and manuals)
  • Learn to type with the help of typing software (e.g. Mavis Beacon Teaches Typing)
  • Learn to identify various programs on the Computer and what they can be used for
  • Learn to use the Computer to find information
• Reasons why ICT is important

  • Acquiring skills in the use of ICT systems prepares people for the present day demands
  • ICT technologies such as the Internet enable people to access and share information
  • Distant learning and online education has become the order of the day thanks to advancements in ICT
  • The knowledge of ICT provides opportunities for people to work both collaboratively and independently in completing different tasks
  • Companies are able to reduce cost of operations and improve efficiency by using the right ICT systems to conduct their businesses
  • With the appropriate ICT systems, information and data can be stored and retrieved more efficiently and reliably
  • The application of ICT to accomplish tasks is not limited to any particular business or industry
  • ICT has become a bridge builder (teacher, student, doctor, nurse, accountant, architect or engineer)
• Fundamental elements of ICT

  • Computer and its allied devices
  • Communication equipment
  • Transmission media
• Information processing


  1. Generation/creation

  2. Storage

  3. Retrieval & manipulation

  4. Transmission & reception (transfer)

  5. Manipulation

  6. Interpretation
• Ways to create information


  • Desktop publishing software e.g. Microsoft Office to create documents
  • Database applications allow you to enter records in a database e.g. MYSQL
  • Video recording device connected to a computer (e.g. WebCam) for videoing
  • Microphone to create voice information
  • Video editing applications to manipulate motion pictures or video
• Storage media for information

  • Computer hard disk
  • USB or Pen drive
  • Writeable Compact Disk or CDROM
  • Magnetic tape
  • Google Drive (a virtual hard disk)
  • Cloud
• Retrieval and manipulation of information

  1. A similar or compatible application is needed to retrieve and manipulate information created using a particular application

  2. For example a word processor is to retrieve and view documents created with the same application

  3. A music file is retrieve using application such as MP3, VLC media player and so on
• Transfer of information


  1. Communications infrastructure such as LAN, Intranet or the internet is required

  2. Information can be sent via email or by using various file transmission applications such as FTP

  3. Files can be copied from one computer to another over a LAN, WAN or the Internet
• Interpretation of information


  • Making sense out of information
  • Ability to use information in accomplishing a particular task
• Data communication


  Communication from a source to a destination, e.g. from one computer to another or from one device to another, involves the transfer of information from the sender to the receiver
• Data communication


  The transfer of data from one machine to another machine such that, the sender and the receiver both interpret the data correctly
• All communication between devices requires that the devices agree on the format of the data
• Protocol


  The set of rules defining a format