Information for study Internet

People always wanted to communicate and share information. That was the main reason for the development of computer network. Computer network is a group of computers that can interact

by means of a shared communication link. There are two types of network:

• Local area network (LAN) is a network where computers are connected together directly, usually by cable. It is used in of­fices etc.

• Wide area network (WAN) is a network of local area net­works connected together. The connection might be a cable or a mixture of cable, fiber optic, and satellite connectivity.

Modem (abbreviation for modulate / demodulate) is a device that allows computers to communicate over ordinary phone lines. It converts digital computer data back and forth for use with analog phone line. There are two types of modems: internal and external. In­ternal means that modem goes inside your computer. External modem is outside your computer and must be plugged into it.

A server is a computer designed to provide various services for an entire network. It is typically either a workstation or a main­frame because it will usually be expected to handle far greater loads than ordinary desktop systems.

The roots of the Internet go to 1969, when the Defense Advanced .Research Projects arm of the Department of Defense created ARPANET for research in networking. The project title was «Resource Sharing Computer Networks». The work centered around the problem in the Department of Defense - how to keep military sites in communi­cation across the country in the event of a nuclear war.

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In the beginning research was the main goal of the system. In 1994 an explosion of direct connections to the Internet occurs. Research is not any more the only purpose of Internet. The In­ternet experiences a steady growing process. Not only universi­ties, research companies and other organizations became part of the Internet, but many of small businesses and homes were connected.

The estimate for year 2000 was 40 million people connected to the Internet and the large majority were home connections in more than 50 countries.

The Internet provides many services. Among them:

• E-mail You can send or receive electronic messages from anyone on the Internet. Anything that can be stored in text file can be mailed.

• File Transfer* The File Transfer Protocol (FTP) provides for the copying of files from one computer to another.

• Communication. You can communicate with the help of the In­ternet with one person or a group of persons simultaneously.

• Information.

On the Internet all addresses / domain names refer to «elec­tronic Addresses», e.g.:

person-id@computer name.domain name

There is never blank space between the components of the Internet address. User ids need not be unique (id - identification), e.g. two people with the same name can have it as login name as long as they operate on separate domains. But the domain name of the computer must be unique, however:

austin@galaxi.isr.umd.edu, austin@euler.berkeley.edu

Austin is the person-id, «galaxy» and «euler» are computer names, «isr.umd.edu» ctnd «berkeley.edu» are domain names. Domain names are composed of sub-domain names: esr, umd, edu.

The table summarizes commonly used sub-domain names:

UNIT 7

In the computer address isr.umd.edu the sub-domain «edu» tells that the computer is located at an educational institution. The sub-domain name «umd» stands for the University of Maryland, and «isr» means the collection of computers at the Institute for System Research, at the University of Maryland.

If you want to send a message put down the word «mail» be­fore the address.

Today computers are seen as indispensable tools not only for computation and typing but for communications. The merging of computation and communications is making essential changes to day-to-day business activities of engineers. Suppose an engineer belongs to a geographically dispersed team. He can:

• Use the Internet / E-mail for day-to-day communications.

• Conduct engineering analyses at remote sites.

Taking Computer for Granted

• Share results among the team members.

• Participate joint ventures assembled over a network, and on­line bidding of projects etc.

Date: 2015-12-11; view: 2560