Introduction Of Computer

 


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Internet and Networks

Computer network is a group of computers linked together, so that they can share information and resources. Internet is “network of networks". It can also be described as information highway. It is the world’s largest network of computers. The networks are related to academics, research, government and include users of all types of profiles i. e. , corporate, individuals, professionals, children, schools, institutes etc. It may be remembered that computer is not located at a single site, not controlled by any central authority. The networking in the internet are not directly connected but interconnected. The ability to graphically access internet resources throughout the web is the primary reason for the phenomenal growth of the internet. It may be noted that WWW is similar to Gopher but instead of being menu driven, it is hypertext based. Most of the problems of WWW are solved through hypertext, which is become generation hypertext.

Client and Server:

The term client refers to the application involved in a communication that actively initiates the contact and the term server refers to the application that passively waits for contact.

Characteristics of clients software:

An application program that performs computations locally

is needed temporarily for remote access

is invoked directly by a user

executes only for one session

runs locally on users computer

can access multiple services

doesn’t require special hardware.

Characteristics of server software:

is invoked automatically at the time of booting

runs on a shared computer

accepts requests from clients

require special hardware and operating systems

can handle multiple clients at the same time.

Host and Terminals:

Host:

A host is a main computer that has all the programs, data and the processing elements. It has its own method of connection.

A terminal may connect to the host and may or may not have the store and forward capabilities.

To connect computers in a network, cables, connector cards and softwares are needed.

TCP/IP: TCP (Transmission Control Protocol) and IP (Internet Protocol) are the two types of protocol. A protocol is defined as a set of standard rules that lets communication between computers take place. The first one TCP (Transmission Control Protocol) is a reliable, connection –oriented protocol that allows stream of bytes from the sender to be delivered to the receiver without error. This is the protocol of the transport layer.

The internet layer defines a protocol called IP (Internet Protocol) to specify an official packet format. Its job is to deliver IP packets to the destination.

The TCP/IP model has five layers:

Application Transport

Network Data link

Physical

Some Protocols and Networks in TCP/IP model

WWW: World Wide Web

WWW is a worldwide hypermedia system. It is the most important feature of the internet. This is commonly called web and is the main reason of popularity of the internet. WWW is a system of internet servers responsible for supporting specially formatted pages and documents. The document follow HTML and support links to the other documents, graphics, audio and videos.

All the internet servers are not essentially the part of WWW. The internet and worldwide web are redefining the global community. Businesses have found a new venue for two way communication with customers in the web site. Not only can businesses advertise, but they also can provide much more information that customers, students and investors usually wouldn’t be able to obtain easily. WWW is a graphical representation of information on internet.

Hypertext:

The web consist of client and server computers that are capable of handling multimedia documents. The client computers use browser software (like Internet Explorer or Netscape Navigator) to view documents. WWW uses HTTP (Hypertext Transfer Protocol) as its underlying protocol. HTTP defines the way messages are formatted and transmitted. HTTP is a stateless protocol. The commands are executed without caring for the previous commands. HTML is an acronym for Hypertext Markup Language. This is the language used to create www pages. The hypertext objects refer to the text and object linked to each other.

URL (Uniform Resource Locator):

URL is an addressing system that is used by WWW as a standard system for specifying a particular site or file on web. It combines information about the type of protocol being used, the address of the site where the resource is located, the sub-directory location and name of the file.

For each web page a URL is specified. This gives a worldwide name of the page.

A URL has three parts

- the scheme (protocol)

- domain name server (DNS) where the page is located

- the filename for the page

When the URL is given, the browser searches for the host name using the DNS and then establishes the connection with the host. The filename is then send over the connection using the protocol specified. The host then returns the page.

The URL scheme is open-ended and can be used for other protocols besides being used for web pages.

Other protocols used in URLs are

- HTTP

- FTP

- News

- GOPHER

- File – for files at local end

- Telnet

- mailto

By: Lalit Bansal

(961)

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