You have already seen in the module on Local Area Networks how computers can be linked together to form networks, enabling them to communicate, share information and resources. While information requirements within a limited area (like an office building or university campus) can be handled by Local Area Networks (LANs), communication requirements beyond that need Metropolitan Area Networks (MANs) or Wide Area Networks (WANs).

In this session, you will see how the services available on Wide Area Networks help in expanding the usage of a PC. The rapid increase of such networks has been responsible for transforming the PC from an information-processing machine into a communications center.

Wide Area Networks may be commercial networks which anyone can subscribe or they may be run privately by companies for their internal use only. There are international networks with thousands of users as well as smaller ones run by local computer clubs. Computer equipment manufacturers have networks to give their customers the latest information on their products. Customers can also report problems or place orders through them.

Networks like CompuServe offer their users (subscribers) many useful facilities like:

  • Communication with other users through E-Mail (Electronic Mail) or FAX (Facsimile).
  • Transfer of files from one computer to another. You may want to send a file to a particular user, or you may want to share a game or utility that you have developed with other users. In such a case, you can upload (send) it to the network, from where other users can download it for their use.
  • Access to centralized databases. These are like libraries on computers containing business, technical or academic information. They have complete text of publications or abstracts that you can browse through, as in a library. Some well known centralized databases are:
    • Dow Jones & Co's Dow Jones News/Retrieval Service.
    • Lockheed's Dialog Information Service. It has 518 separate databases covering science, engineering, business and economics.
    • Mead Data Central's NEXIS/LEXIS. It offers full text from 15 newspapers like New York Times and 31 magazines like Byte, Newsweek and Business Week, etc.
    • West Publishing Co's Westlaw. It allows lawyers to browse through court cases and federal regulations.
  • Special Interest Groups (SIGs) or forums where you can ask questions, get responses and exchange information about your specific areas of interest, that could be medicine, cricket or computers.
  • On-line services offered by various banks, airlines and shopping centers allow you to transact with them through the network.
  • Support forums maintained by various hardware and software companies provide technical expertise and solutions to problems to their customers.
  • Computing Time, i.e. allowing you to link to mainframes and utilize their processing capacity.

Wide Area Networks that offer such services are called Bulletin Board Services (BBSs).