Information Technology and You 165on the network must have a network interface card if it is connected to a LAN,
or a modem if it is connected through telephone lines. When a series of LANs
in different cities are interconnected, they form a wide area network, or
WA N. Large businesses w ith facilities around the countr y or world net work
their users’ personal computers together in a series of LANs that are further
interconnected into a large WAN. The largest WAN, the Internet, connects to-
gether millions of computers of commercial companies, government agencies,
schools, colleges and universities, and nonprofit agencies around the world.
Preventing unauthorized people from accessing confidential information
is one of the biggest challenges posed by networks. To do so, people and orga-
nizations use special security software. One technique, a fire wall, allows out-
side users to obtain only that data which is outside the “fire wall” of the file
server; subsequently, only people inside the company may access information
inside the fire wall.
Electronic Mail (E-mail)
E-mail is the most popular network application because it has become the
method of choice for communicating over both short distances (interoffice)
and long distances. It allows you to send communications to any other person
EXHIBIT 5.7 Diagram of client-server network.
Ethernet/WinNT NetworkUser PC User PC User PCFile server Print server Internet/mail serverLaptopLaptopPrintersInternetFilesFiles