Lesson Objectives

• To learn why you might want your computer to be part of a network
• To learn what computers on a network can share and how they let computer users on a network communicate with each other
• To learn about the two major types of computer networks
• To learn how computers are connected in a network
• To learn how and why a computer network may be closed or only allow limited users access

The Lesson

Computer Networks Around Us

The stand-alone computer you are using has many capabilities to help you in becoming an information literate person. When your computer joins with other computers, however, it becomes even more powerful. When computers join together, they are said to be on a network. And computer networks are all around us.

Computer networks are what allow:

• Tina Papadakis, the cashier at the Rite Aid Drug Store, to scan the code on the bottle of Scope into her computerized cash register at the front of the store and see the price that was entered at a computer in the backroom when the Scope shipment was received.

   

• Jonathan Bowen, a reservations clerk at the Northwest Airlines reservation counter at Kennedy Airport in New York City, to see if Tameka Washington will be able to get a seat when she changes planes in Atlanta, Georgia.

   

• Students in a word processing class at community college to all use Word Perfect at the same time, even though there is just one copy of the software.

   

• Ginny Rodriguez, a student at Los Alamos High School in New Mexico, to talk to Reba Tannenbaum at Central High School in a suburb in Massachusetts while using the World Wide Web.

   

Why Join a Network?

Just as computers seem to be appearing in more and more homes and every desk you see is furnished with a computer, computer networks, too, are surrounding us as a part of nearly every business and organization we encounter. The major reasons for computers to be connected on a network is to allow for sharing of information, equipment and software and for communication.

Sharing Information

Tina and Jonathan in the examples above are both able to find out information through their networked computers. Tina uses her computerized register to get pricing information about the stock in the store. Jonathan uses his computer to get information about seating on a distantly located airplane. Both Tina and Jonathan are using computers to seek out the information from a centralized electronic source.

There are many advantages to computers on a network being able to get information from a central source. Changes that are made to the information need only to be made in one place. More than one person needing to see the information can see it at once. In addition, computer networks allow people who may be physically distant from the information they need to see the information as though it is stored locally.

Visit the Exploratory: Plan A Party!

Sharing Equipment

The computer you are using now may not have a printer attached to it but because your computer is on a network, you are able to use a printer, located somewhere centrally in your classroom, that is available to all the computer users in the room.

There is an advantage to all computers in a network sharing large, expensive pieces of computer equipment such as printers. The single printer that was purchased to work with all of the computers in your classroom is a better quality printer than smaller ones that might have been purchased to work with each individual computer.

Sharing Software

Computers on a network can share software, too. When you use your computer by itself, the software is kept on one of your storage devices, such as the hard drive, until you are ready to bring it into RAM. When computers are on a network, software may be loaded on a single computer that works as a file server. The file server works with the client computers, distributing information to them or performing functions for them as requested. The community college that offers the word processing course would keep the Word Perfect software on its network file server and distribute it as requested.

Sharing software on a network has advantages. A single copy of the software is all that needs to be stored. Computer users on the network that have access to the programs on the server can use or download the software from this central location. At any time, the computers on the network may be running different software or using the same software.

Exercise: Join A Software Discussion Group.

Communication

Computer users on a network can also communicate with each other by sending electronic messages from one computer to another (e-mail) or by writing messages to each other in real-time (chatrooms on the Internet).

Advantages of electronic communication include the ability to transmit messages quickly, to send messages to multiple people at once with little effort, to forward messages easily, and to read messages at one's convenience. Ginny Rodriguez in the illustration above communicates electronically with Reba Tannenbaum.

Local Area Networks (LANS) Vs. Wide Area Networks (WANS)

There are two types of computer networks that are commonly in use in the stores, offices, schools, hospitals, libraries and other public places we go every day. The first type of network is called a local area network (LAN). The second type is called a wide area network (WAN).

A local area network is created when stand-alone computers that are physically close together, such as in adjacent buildings, in a single building, on a floor of a building, or in a particular area of a building, office or school are connected. Computers connected in a LAN are often referred to as workstations. The computers used in a store such as Rite Aid and in the community college classroom are examples of computers on a LAN.

A computer becomes part of a wide area network when it is able to connect with computers at a distance, anywhere from across the street to across a state, a country or an ocean. The reservation system at the airport and Ginny Rodriguez's connection to Reba Tannenbaum are examples of computers on a WAN.

Visit the Exploratory: Send a Message to your Network!

Getting Connected

The connection of a computer to a network may be temporary or long-term.

A single computer, such as one that you might have in your home, can connect with a wide area network through a modem. A modem is a device that hooks a computer into telephone lines. A modem connection is usually temporary. Ginny and Reba are able to chat by using a modem on each of their computers.

Modems come in different speeds. The speed of transfer is measured in terms of Kilo bits. Currently, the fastest computer modem runs at 56 Kilo bits per second.

Computer on a LAN are equiped with a network card and cabelling to make them part of their own network. The connection is intended to be long-term.

When computers are on a local area network, they can be connected through their LAN to a wide area network without using a modem. Other methods of connecting computers at a distance to the telephone network include ISDN (Integratated Services Digital Network) connections and T-1 lines.

The computers in the community college classroom and in your classroom are connected in a LAN that allows them to share and communicate within the one room. Additionally, a T-1 line connects the LAN to telephone lines, extending the networking capability of each of the computers.

LANS and WANS As Closed Computer Networks

Local Area and Wide Area Networks can be set up as closed computer networks. A closed computer network is a network that is intended to allow only certain people to have access to the information and software shared in the network. Initially, however, limiting access requires using technology to specify the computers that will be allowed to be in the network, rather than the people. Other steps must be taken then to assure that only designated people can use the computers on the network.

A LAN can be more easily set up as a closed computer network than a WAN. The technicians or engineers who create the network wire and configure selected computers to be able to communicate with each other. These people see and handle every computer that will participate in the closed network. Assuring that no unauthorized users will use the LAN requires that those people allowed to use computers on the LAN be assigned or choose a password. The software that regulates the computers on the LAN will lock off all computer functions until this passwork is given by a person using one of the computers.

When an individual computer or computers in a LAN are attached to telecommunications lines, or reach out to become part of a WAN, assuring that this larger network remains closed requires more technology. Passwords are also used to keep a WAN network closed. Another feature that enable computers on a WAN to be closed is called a firewall.

Reasons vary for why people would want to create a closed computer network. These are some of the common situations where a closed computer network might be used:

• An employer may want to limit the activities of employees working with company computers to using only the software programs that the company makes available on its LAN file server or to a limited number of resources from the outside if the LAN is attached to a WAN. Employers are concerned that employees are playing with game software or visiting recreational Internet sites during work hours.

   

• Some companies want to assure that the information exchanged between people using computers in their office LAN remains private and available only to people working in that office. Company records and inter-office e-mail can be protected if the network is closed.

   

• A business may want to create a closed network so that only its customers or suppliers can have access to the information available on the networked computers. This information usually records the activities of the customers or suppliers. The ATM, or automatic teller machines, in a bank are examples of this type of network.

• Some businesses make information and activities available through a computer network that is only open to people who have paid a fee or bought a subscription to gain access to the network. Closing the network keeps non-payers out. Online Service Providers, such as America Online, CompuServ, Prodogy and the Microsoft Network are examples of such closed networks.

Exercise: Join A Network Discussion Group.

In contrast to closed computer networks, the Internet is an example of what many see as an open computer network. After you complete the quiz for this lesson, you will move on to a sequence of lessons discussing the Internet.