What is a Computer Network? Evolution from ARPANET to the Internet

Hello students, welcome to Kwickprep. You send a photo to a friend in another city, and it reaches in one second. How does that happen? The answer is a computer network. Today we will learn what a network is and how the Internet was born. We will also see its good and bad sides, and two ways to build one.

Let us start with the meaning. A computer network is two or more devices connected together. The link can be a cable, or a wireless signal like Wi-Fi. Connected devices can share data, messages and resources like a printer. Every device on a network, such as a laptop, phone or printer, is called a node.

Why do we connect computers at all? First, to share files and data in seconds, instead of carrying a pen drive. Second, to share costly devices, so one printer can serve a whole school office. Third, to communicate through email, chat and video calls. Fourth, to reach information kept far away, like your exam result on a board website. Fifth, sharing saves money, because not every desk needs its own printer.

Look at the difference a network makes. To send a marks list, you once carried a pen drive, but now you email it in seconds. To print, every desk needed a printer, but now one shared printer is enough. To talk to a cousin abroad, you posted a letter, but now you make a video call.

Now let us travel back in time. In nineteen sixty nine, a project of the United States defence department started Arpanet, which first linked four computers at research sites. In nineteen eighty three, Arpanet switched to T C P slash I P, a common set of rules that still runs the Internet. In nineteen eighty six, the National Science Foundation built N S F Net, which linked universities and research centres at higher speed. In the nineteen nineties, the World Wide Web arrived and businesses were allowed to join. In India, Videsh Sanchar Nigam Limited started public Internet service on fifteenth August nineteen ninety five.

Let us fix four key terms from this story. Arpanet was the first such network, built by the research agency of the American defence department. N S F Net was a faster network that joined many universities, and it later became the backbone of the Internet. A protocol is a set of rules that devices follow to talk, just as a class follows rules to speak one at a time. The Internet is a network of networks, joining millions of smaller networks across the world.

Pause the video and try this quick question. Which came first, Arpanet or N S F Net? The answer is Arpanet, in nineteen sixty nine. N S F Net came later, in nineteen eighty six, and exams often ask this order.

Now let us list the advantages clearly. Resource sharing means many users use the same printer, scanner or storage. Data sharing means one updated copy of a file is used by everyone, like a school attendance sheet. Communication becomes fast and cheap through email, chat and video calls. Costs go down, because fewer devices are needed. And backups can be taken from one central place, so data is safer from loss.

Every connection also opens a door, so networks carry risks. A virus, which is a harmful program, can spread from one computer to all the others. Hackers, people who break into systems without permission, may steal data. Personal details like phone numbers can leak, and that is a loss of privacy. If the main computer fails, many users cannot work at all. And a network needs skilled people and money to set up and look after.

We can reduce these risks with simple habits. Use strong passwords, and never share a one time password with anyone. Keep antivirus software and system updates switched on. Use a firewall, which is a guard that blocks unwanted traffic from entering the network.

Networks are built in two main ways, and first we need three words. A client is a computer that asks for a service, like your phone asking for a web page. A server is a powerful computer that gives the service, like the website's computer sending that page. A peer is an equal computer that can ask and give at the same time.

Let us look at the first model, which is client server. In this model, one central server serves many clients. The server stores the data and decides who may see what, so security is strong. Think of the railway ticket booking website, where lakhs of phones ask one set of servers for seats. The weak point is clear: if the server goes down, every client has to wait.

Now the second model, called peer to peer. Here, all computers are equal and there is no central server. Each peer shares its own files or printer directly with the others. Two phones sending a song over Bluetooth form a tiny peer to peer network. It is cheap and easy to set up, but security and backup are weak, because nobody is in charge.

Here is the comparison that exams love to ask. Client server has a central server, while peer to peer has none. Client server gives strong security, peer to peer gives weaker security. Client server costs more, because a server is expensive. Client server suits large networks, and peer to peer suits small groups of a few computers. Banks and railway booking use client server, while sharing files at home is peer to peer.

Let us revise what we learned today. A network links devices so they can share data and resources. Arpanet began in nineteen sixty nine, N S F Net followed in nineteen eighty six, and together they grew into the Internet. Networks give sharing, fast communication and lower cost. They also bring viruses, hackers, privacy loss and server failure. Client server uses a central server, while in peer to peer every computer is equal.