Chap 1-2

• Data communications


  Any process that permits the passage from a sender to one or more receiver of information of any nature
• Information


  Knowledge or intelligence
• Data


  Information that is stored in digital form
• Types of data


  • Alphabetic
  • Numeric
  • Symbolic
• Forms of data


  • Binary-coded alpha/numeric symbols
  • Microprocessor op-codes
  • Control Codes
  • User Addresses
  • Program Data
  • Data Base Information
• Data communication


  The process of transferring information presented digitally (usually in binary form) between two places
• Data communication is often referred to as computer communications, because computers or computer peripherals are involved
• The information can be in analog form, such as human voice or music, or in digital form, such as binary-coded numbers or alphanumeric codes
• Data communication network


  Systems of computers and computer equipment, can be as simple as a computer connected to a printer or two personal computers connected through public telephone network
• Invention of telegraph and development of Morse Code

  1837
• Samuel F.B. Morse


  • With Telegraph, DOTS, and DASHES are transmitted across a wire using Electromechanical Introduction. A various combination of Dots and Dashes were used to represent binary codes for letter, Numbers and Punctuation
• First Telegraph line was established between Baltimore and Washington, D.C


  1844
• The first slow-speed telegraph printer was invented


  1849
• The Western Union Telegraph Company was formed in Rochester, New York


  1850
• Emile Baudot invented a Telegraph Multiplexer which allowed signal from up to Six different telegraph machines to be transmitted simultaneously over a single wire


  1874
• Telephone was invented by Alexander Graham


  1876
• Bell Laboratories developed the First Special Computer


  1940
• Remington Rand Corporation built the UNIVAC (UNIVersal Automatic Computer)


  1951
• The AT&T operating tariff allowed only equipment furnished by AT&T to be connected to AT&T Lines. During this time a landmark supreme court decision, the Carterfone decision, allowed non-Bell companies to interconnected to the vast AT&T communication network

  1968
• Internet


  A public data communications network used by millions of people all over the world to exchange business and even personal information
• Intranet


  Private data communications networks used by many companies to exchange information, resources and software applications among employees
• World Wide Web (WWW)

  A server-based application that allows user/subscriber to access the services offered by the web. Browsers, such as internet Explorer, Mozilla, Firefox and Google Chrome, are commonly used for accessing data over the WWW
• General classification of equipment used in data communication

  • DTE - Data Terminals/Terminating Equipment
  • DCE - Data Circuits-Terminating Equipment / Communicating Equipment
• DTE - Data Terminals/Terminating Equipment


  It can be virtually any binary digital device that generates transmits, receives, or interprets data message. It is where information originates or terminates
• DCE - Data Circuit-Terminating Equipment/ Communicating Equipment


  Any device that transmit or receives data in the form of an analog or digital signal through a network. It is a general term that describes equipment that converts Digital Signal to Analog Signals and interface the DTE to the analog transmission medium. Modem is an example of DCE. it Converts binary digital signals to analog signals such a FSK, PSK, and QAM and vice versa
• Network


  A collection of devices that is connected to each other and able to communicate. Two devices are said to be networked when a process in one device is able to exchange information with a process in another device
• A network allows communication and data exchange/sharing between systems, software applications, and users. The devices that are involved in the network that originate, route, and terminate the data are called nodes
• Five components of data communication

  • Message
  • Sender
  • Receiver
  • Transmission Medium
  • Protocol
• Message


  The information (data) that needs to be transferred. Popular forms of information include text, numbers, pictures, audio, and video
• Sender


  The device that sends the data message. It can be a computer, workstation, telephone handset, television
• Receiver


  The device that receives the data message. It can be a computer, workstation, telephone handset, television
• Transmission Medium


  The physical path by which a message travels from sender to receiver. Examples include Twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves
• Protocol


  A set of rules that govern data communications. It represents an agreement between the communicating devices. Two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese
• A computer network is a collection of computers, printers, routers, switches, and other devices that are able to communicate with each other over some transmission media
• Benefits of networks


  • Resource sharing
  • Reduced cost and easier installation of software
  • Improved communication
  • Improved flexibility
  • Improved security
• Resource sharing


  Anything that a user on one node may want to access on the other nodes, such as files, folders, printers and scanners. This helps to increase the productivity of a working group
• Reduced cost and easier installation of software


  Many software products are sold to organizations on a network basis, allowing a single copy to be purchased for the network and number of seat licenses to be added, resulting in cost savings
• Improved communication


  Without the internet, email, instant messaging, video chatting, conferencing, and social media, exchange of information would be very slow. Distance is no longer an obstacle to communication
• Improved flexibility


  Users are no longer tied to a single computer. If resources are stored on a server, a computer problem is no longer a problem for a user to be unable to do their work, as they can move to any other computer that is part of the network and access their files on the server
• Improved security


  Shared resources can be secured with restrictions on who can access them and what kind of access an individual can make