Introduction To Networks Lecture 2 Notes

Introduction

This lecture is prepared by Salman Ahmad, a teacher and web developer, with the aim of making the subject of Computer Networks and Data Communication simple, clear, and exam-friendly for students of Class 9. While textbooks often give short definitions, these notes explain concepts with examples, applications, and real-life use cases.

Computer networks are the invisible systems that allow us to connect with the world. Every time we send a message, watch a video online, attend an online class, or even transfer a file, we are using a network. Data communication is at the heart of this process. To understand modern computing, it is impossible to ignore these topics. This lecture is a step-by-step journey into the basics of networks and communication systems.

History & Importance

Extra[You can skip this during writing on notebooks. It is just an extra knowledge.]

The idea of connecting computers began in the 1960s, when the U.S. Department of Defense started a project called ARPANET. This later evolved into the Internet. At first, networking was only used by scientists and universities, but today it has become a part of daily life. From smart homes and banking systems to e-learning and online shopping, networking enables everything.

Without networks, computers would remain isolated machines, and communication would be limited to physical transfer of data using USBs or disks. The importance of computer networks lies in saving time, improving communication, and making global collaboration possible.

Full Definitions

Objectives of Computer Networks

The main purpose of a computer network is to allow devices and users to share resources, communicate, and collaborate effectively.

• Resource Sharing: Networks allow multiple devices to share resources (printers, storage, etc.), reducing costs and increasing efficiency. Example: In an office, several computers share one printer instead of each having its own.
• Data Communication: Networks enable the transfer of data between users, making communication faster and easier through emails, instant messaging, and video conferencing. Example: Teams in different countries use Zoom or Microsoft Teams to collaborate.
• Connectivity & Collaboration: Networks connect devices, making remote work and teamwork possible through real-time access to shared documents and cloud services. Example: A group edits a document together using Google Drive.

Fundamental Concepts in Data Communication

Data communication is the process of exchanging data between a sender and a receiver through a medium, using a defined protocol.

5 Components of Data Communication

• Sender: The device that sends the data. Example: A computer sending an email.
• Receiver: The device that receives the data. Example: A smartphone receiving the email.
• Message: The actual data being communicated. Example: The text/content of the email.
• Protocol: The set of rules that governs data communication. Example: HTTP (used for websites), SMTP (used for emails).
• Medium: The channel/path through which the data travels (wire or wireless). Example: Ethernet cable, Wi-Fi, or fiber optic cable.

Applications of Networks

Extra[You can skip this during writing on notebooks. It is just an extra knowledge.]

Networks are not just theoretical concepts; they play a role in nearly every field. In education, students attend online classes. In healthcare, doctors use telemedicine to treat patients remotely. In businesses, teams collaborate using shared platforms. Even entertainment, like Netflix and YouTube, would not exist without strong networking systems.

• Education: E-learning platforms like Google Classroom rely on networks.
• Healthcare: Patient reports are shared online for faster diagnosis.
• Banking: ATMs and online banking depend entirely on secure networks.
• Social Media: Facebook, WhatsApp, Instagram connect billions daily.

Comparison: LAN vs WAN

Extra[You can skip this during writing on notebooks. It is just an extra knowledge.]

Feature	LAN (Local Area Network)	WAN (Wide Area Network)
Area Covered	Small (Home, Office, School)	Large (Cities, Countries, Internet)
Ownership	Usually private	Public or private
Speed	High speed	Comparatively slower
Cost	Low installation cost	High installation and maintenance cost

Quick Notes – Computer Networks & Data Communication

• Objectives of Computer Networks:
  • Resource Sharing → Multiple devices share hardware/software (printers, files, storage) → reduces cost & improves efficiency. Example: Many office PCs use one printer.
  • Data Communication → Exchange of information through emails, chat, or video calls. Example: Zoom/Teams meetings between offices.
  • Connectivity & Collaboration → Devices stay connected for teamwork, remote access, and real-time editing. Example: Teams working on Google Drive docs together.
• Data Communication Definition: The process of transferring data between a sender and receiver using a medium under specific rules (protocols).
• Essential Components:
  • Sender → Origin device (e.g., computer sending an email).
  • Receiver → Destination device (e.g., smartphone receiving an email).
  • Message → Actual data/information (e.g., content of the email).
  • Protocol → Rules of communication (e.g., HTTP for web, SMTP for email).
  • Medium → The path through which data travels (e.g., Ethernet cable, Wi-Fi, fiber optic).

MCQs

1. Which of the following is NOT an objective of computer networks?
   a) Resource sharing
   b) Data communication
   c) Printing hard copies ✅
   d) Collaboration
2. The Internet is an example of:
   a) A small LAN
   b) The world’s largest network ✅
   c) A private WAN
   d) Only a wireless network
3. In computer networks, sharing a printer among multiple users is an example of:
   a) Data communication
   b) Resource sharing ✅
   c) Collaboration
   d) Message transfer
4. Which component of data communication is responsible for sending the data?
   a) Receiver
   b) Sender ✅
   c) Protocol
   d) Medium
5. HTTP is an example of which component of data communication?
   a) Message
   b) Medium
   c) Protocol ✅
   d) Receiver
6. In data communication, what does the “medium” represent?
   a) The data itself
   b) The set of rules
   c) The device receiving the data
   d) The path through which data travels ✅
7. When two people collaborate in real-time on a Google Docs file, which objective of networks does this represent?
   a) Data communication
   b) Resource sharing
   c) Connectivity & collaboration ✅
   d) Protocol usage

Summary

This lecture highlighted the objectives of computer networks and the fundamentals of data communication. Networks are not only important for exams but also for real-life applications. By understanding the components such as sender, receiver, medium, message, and protocol, students can clearly grasp how data is exchanged across devices. With quick notes and MCQs, you now have a solid foundation for both theory and practice.

Frequently Asked Questions