Internet – Study Material


Internet – Study Material

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The Internet is a massive body of networks, a networking infrastructure. It connects millions of computers together globally, forming a network in which any computer can communicate with any other computer as long as they are both connected to the Internet. In other words, it is a global system of interconnected computer networks, connecting millions of computers through which exchange of information such as data, news and opinions etc. is possible. It uses the TCP/IP (Transmission Control Protocol/Internet Protocol) to serve billions of users worldwide. So, TCP/IP can be called backbone of Internet It is a network of networks that consists of millions of private and public, academic, business, and government networks. The Internet is often called “The Information Highway,” that implies that there is a straight, clear path of obtaining information. It connects thousand of computer networks. Each computer in Internet is called a host, is independent. Through telephone wires, Fiber optical cable and satellite links, Internet users can share variety of information.

Equipment required for using Internet

  1. Computer 2. Modem
  2. Web browser 4. Telephone line
  3. Internet service provider (ISP)

Computer: Any good IBM compatible, Macintosh or UNIX computer that has good storage space 4 GB or more hard disk, 32 MB RAM and 300 MHZ processor.

Modem: It is a short form of modulator and demodulator. To connect the Internet through telephone or telecommunications line a modem is required. It is a link between Internet service provider and browser. Our computer sends data in binary code to our modem which converts the binary-coded data to an analogue signal. This data then travels along the telephone network. When the data reaches the destination computer, the modem connected to that computer converts the analogue signal back into binary coded data which can be read by destination computer. Thus the modem transmits data in pulse form over the network through telephone line. To maintain compatibility in between computer system and telephone line needs modem which converts digital signal to analog signal and analog signal to digital signal. The speed of modem measures in BPS (Bits Per Second).

There are two types of modems:

(i) External Modem and          (ii) Internal Modem.

The External Modem has to be connected to our computer and telephone line with cables and electric socket while the Internal Modem is already built inside our computer. The billing of our telephone starts from the moment we get connected to Internet. So a modem with good speed ensures low telephone bills.

Web Browser: Web Browser is a software that is used to navigate the world wide web. It connects computer to Internet. Before, start working on the Internet, we make sure that we have a web browser in our computer otherwise, we will not be able to surf the net. The most popular types of browser today are Netscape Navigator and Microsoft Internet Explorer, Mozilla Firefox, Safari, Opera, Chrome etc. We can get available resources from any location through visit site of that location. Each location has a unique address called URL (Uniform Resource Locator), which we type in Web Browser to get resources.

Internet Service Provider (ISP): ISP is an organisation that provides Internet access to users. If we have a computer with a web browser, a modem and a telephone line connected to our computer, we also need an Internet connection. We can get an Internet connection from various ISPs. Earlier in India, Internet connection was only available through. VSNL (Videsh Sanchar Nigam Limited). Now, we can choose from popular Internet service providers of India such as VSNL, BSNL, Satyam online, Mantra on Line, MTNL etc. These companies have DNS servers in different cities of India. DNS server is a computer which translates domain name to IP address.

At present BSNL provides the following types of connections to access Internet to users.

  1. PSTN: Public Switched Telephone Network
  2. ISDN: Integrated Services digital Network
  3. Leased line access
  4. Direct Internet Access (DIAS)
  5. Account free Internet dial up access based on CLI
  6. Broadband connection: Broadband service is based on DSL technology (on the same copper cable that is used for connecting telephone).This provides high speed Internet connectivity up to 8 Mbps. This provides continuous Internet access service with speed ranging from 256 Kbps to 8 Mbps.
  7. Wi-Fi: Wi-Fi Services have been introduced for providing high speed Internet access at convenient public locations such as like Airports, Railway Stations, Universities and their campus etc.
  8. Sanchamet card: BSNL has also launched “SANCHARNET CARD” recently. The Sanchamet Card is a prepaid Internet Access Card for users.

Uses of Internet: Internet has become a part of our everyday life. From being used in defence purposes by the United States military for communication initially, to being used world wide for hundreds of thousands of different purposes of our every day life now.

There are millions of applications of Internet and we are in fact as dependent on Internet as we are on other utility things like electricity, water etc. Before a few years, people used to get up in the morning and read the newspaper or watch television. Now most people log onto the Internet first thing in the morning. So Internet has become so essential in our daily life.

Internet related terms

  1. URL: URL stands for Uniform Resource Locater. It is a standard way to locate a resource such as file or document on the Internet. The URL specifies the address of a file and every file on the Internet has a unique address. Every URL consists of three parts. The first part of the URL contains the name of the protocol to be used to access the file resource, the other is IP address or domain name that identifies a specific computer on the Internet. Such as a URL is http:/ / in which http is protocol and is IP address or the domain name where the resource is located.

The actual URL is a set of four numbers separated by periods. An example of this would be but as these are difficult for humans to use, addresses are represented in alphanumeric form that is more descriptive and easy to remember. The Internet Domain Name System translates the alphanumerical address to numeric.

  1. World Wide Web (WWW): It is commonly known as Web, is a way of accessing information over the medium of the Internet. In March 1989, Tim Berners-Lee played an active role to develop the World Wide Web. World Wide Web is interlinked hypertext documents that contain resources. It is a vast collection of information related pages called web pages. Web pages are written in HTML (Hyper Text Markup Language) computer Language. Each page may contain text, images, videos, sounds and other multimedia and navigate between them using hyperlinks. Mouse pointer appears like a hand when it points to a hyperlink. A hyperlink which is often called link is the “address” to a document or a resource on the web. When we click it then it makes available the resources of linked web pages. To reload a web page, we use reload button.
  2. Web server: For a web site to be available to everyone all over world at all times, it needs to be stored or hosted on a computer. Such a computer is known as a web Server. A web server can mean two things, a computer on which a web site is hosted or stored and a program that runs on such a computer and can send web pages out to other computers over Internet. But the most important is to have a Permanent Internet address also known as an I.P. address. If the I.P. address changes, the web site would not be found and will appear off line, the browser will display an error ‘cannot find web site’.
  3. Bookmark: A bookmark is a saved link to a Web page that has been added to a list of saved links. When we are looking at a particular Web site and want to be able to quickly get back to it later, we can create a bookmark for it. If we are going to a site that we often use, instead of having to type in the address every time we should bookmark it.
  4. HTML (Hyper Text Markup Language): It is a computer’s language used to create hypertext documents for the World Wide Web. Web pages are created using HTML.
  5. TCP/IP (Transmission Control Protocol / Internet Protocol): TCP/IP is the communication protocol for the Internet, it defines the rule which computers must follow to communicate with each other over the Internet.
  6. FTP (File Transfer Protocol): It is a standard network protocol used to exchange and manipulate files over the Internet. FTP represents the network functionality that enables users to upload web page files like simple text files, images, multi-media files, etc. from their personal computers to the server where their websites are located and vice versa – to download files from a particular server to their own machines.
  7. HTTP: It is short for Hyper Text Transfer Protocol, used by the World Wide Web. HTTP defines how messages are transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when we enter a URL in our browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page.
  8. ICMP (Internet Control Message Protocol): It is one of the main protocols of the internet protocol suite. It is used by network devices, like routers to send error messages.
  9. IP address: The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, could be an IP address. It is an identifier for a computer on a TCP / IP network.
  10. Domain name: Domain names are specific names used in URLs to identify particular Web pages. A name that identifies one or more IP addresses. For example, in the URL, the domain name is Every domain name has a suffix that indicates which top level domain it belongs to. There is only a limited number of such domains. For example:

.aero: aviation

.gov: Government agencies

.in: India

.org: organisations (nonprofit)

.com: Commercial business

.asia : Asia

.jobs: Jobs

.name: Personal

.edu: Educational institutions

.mil: Military

.net: Network organizations

.biz: Business organisation

  1. Upload: The term upload can refer to the

sending of data from a local system to a remote system such as the remote system should store a copy of the data being transferred. When we are sending the copy of file from our system to a remote system by using Internet, then we are uploading the files.

  1. Download: The term download can refer to the receiving of information to a local system from a remote system or server on the internet. When we are receiving a copy of the file from a remote system to our system by using Internet, then we are downloading the files. Software piracy is the act of copying or down loading a program from a network and making multiple copies of it.
  2. Gateway: A gateway is a network point that acts as an entrance to another network. A gateway can accept a packet formatted for one protocol and convert it to a packet formatted for another protocol before forwarding it.
  3. Flash: Flash is a vector animation software, originally designed to create animations for display on web pages. It is a small application that allows animations, interactive forms, games etc. It is to be embedded in web pages.
  4. Web Surfing: Internet is a necessity for today’s computer users. It is the world’s largest encyclopedia. Whatever we need, we can find it and download it over the Internet, often for free. To search and explore the resources from websites which we need is called web surfing. Web surfing is usually seen as fun, dangerous, or a tremendous waste of time.
  5. Virus: A computer virus is a computer program that can load and replicate itself without even the user knowing about the damage being done. It infects a computer system. It replicates by being copied and uses all over memory, resulting into system being slow or crashes. Some viruses are initiating its copying to another program such as computer boot sector or document. If our computer keeps rebooting itself, then it is likely that if has a virus. It can be transmitted as attachments to an e-mail or in a downloaded file and it is the most common way to get a virus in computer. So, if we get an e-mail from unknown user we should erase it without opening. It is a program designed to destroy data on computer system, which can travel to infect other computers. As with all code, viruses use the host’s resources memory and hard disk space amongst others, and are sometimes deliberately destructive such as erasing files, formatting hard disks or allowing others to access the machine without authorization across a network. If a virus corrupts the file allocation table, the operating system DOS cannot retrive any data from the dist. File allocation table provides a map of clusters in which the file has been stored.

Viruses are categorized to several parts based on then features

(a) Boot Sector Viruses

(b) Macro Viruses

(c) Multipartite Viruses

(d) Link Virus

(e) Parasitic Virus

(f) Worms

(g) Trojansor Trojan Horses

To prevent, detect and remove these computer viruses a software is used which is called anti-virus. Such software may also prevent and remove adware, spyware and other forms of malware. It also provides the facility of auto-protection and real time protection which detects the virus in files before downloading from Internet. If virus activates then it informs the user by pop-up window and after that user removes it by system scan. To protect from virus the computer system needs periodically full scan.

The first actual computer virus was the Creeper, which first showed up on a very early edition of the Internet, the ARPANET. ‘Happy Birthday Joshi’, virus was first discovered in India in June 1990. Brain was the first virus to hit computers running Microsoft’s then popular operating system MS-DOS. Elk Cloner is regarded as the first virus to hit personal computers worldwide, it spread through Apple II floppy disks.

Some computer viruses are

  1. Creeper
  2. Brain
  3. Monkey
  4. Michelangelo
  5. Hacker: A person who used his or her

expertise to get access to other people’s computers to get information illegally or do damage for personel gain.

  1. Phshing: Phishing is a way of attempting to acofuire sensitive information such as username, password and credit card details. Phishing scams attempt to trick people into providing sensitive personal information. In order to carry out this trick the phishing scammers send a fraudulent email disguished as an official reguest for information from the targeted company. They also create a lookalike website that is designed to closely resemble the target company official site.