what can internet do for us? internet has four main applications as follows: 
　　l. e－mail. with internet, people can compose, send, and receive electronic mails. many people get dozens of messages a day and consider it as their primary way of interacting with the outside world, far outdistancing the telephone and snail mail.
　　2. news. newsgroups are specialzied forums in which users with a common interest can  exchagne messages. thousands of newsgroups exist on internet,on technical and nontechnical topics,including computers, science, ecreation, and politics. 
　　3. remote login. using the telnet,rlogin, or other programs, the  user anywhere on  internet can log into any other machine  on  which  he  has  an  account. 
　　4. file transfer. using the ftp program, it is possible to copy files from one machine on internet to another. vast numbers of articles, databases, and  other information are available in this way. 

the network computer
　　the network computer, also known as the internet toaster,internet appliance or internet device,is the low cost,no　maintenance desktop device. it allows users to effortlessly connect to　internet and network resources. from there, they can share any　resource and perform all computing tasks that they currently do on　their pcs. 
　　the network computer offers simplicity. stripped of the　hardware and software that　complicate the pc life and only capable of network access and display, the network computer relies on the network for virtually all software, services, processing, data, and resources. it eliminates the continuous cycle of desktop hardware and software upgrades, pushing that burden instead on to the network. 
　　need the latest word processor or spreadsheet? run it off the server, want to save your work?  just send it off to the network, where it will be stored secured, and backed up.

firewall: a measure of network security
　　with the popularity of internet,it is increasingly difficult to guarantee the network security. sometimes the network  was breached because of not only hackers’ visit but also authorized users’ care out of ordinary. firewall just is an effective measure of network security. it will ensure that all communications conform to your security policy. 
　　once two lads broke into the university network,created a bulletin board,loaded popular commercial software on it and invited users across internet to download the packages. thanks to a firewall, network administrators found the system breached. they checked the audit and found the students’ ip addresses, names and location. the police arrested the two hackers.

e－mail
　　one important application for internet is communication between computer users by the electronic mail, or e－mail. e－mail allows users to electronically transmit and receive messages, text, or data. e-mail functions futher like a mailbox: the user can send messages whether or not the intended receiver is currently on the network and the message is stored, along with a signal for the receiver that indicates that there is a message waiting.
　　e-mail has replaced the telephone for many messages. users can respond when it is convenient,without being interrupted,  and can get their message either on-screen or in the printed form.

electronic bulletin boards
another interesting application for internet is the electronic bulletin board which is also called bulletin board service, bbs for short.it allows users to post and retrieve messages that are not directed to a specific user, much like announcements are posted on an office bulletin board. bbs has been used for everything from dating service and want ads to highly specialized applications such as the exchange of research data in a narrow scientific field.