A computer network is a system where multiple computing devices, such as computers, servers, routers, and switches, are interconnected to share data, resources, and services like files, printers, applications, and the internet. These networks can range from small local area networks (LAN) in a single building to extensive wide area networks (WAN) that connect cities or continents. By using communication protocols, these devices exchange information efficiently, enabling user access to shared resources, facilitating collaboration, supporting remote work, and fostering innovation through real-time communication and data sharing in today’s digital age.
Key Historical Facts & Firsts
Topic
Fact
Father of Computer Networks / Internet
Vint Cerf & Bob Kahn
First Network Technology
ARPANET (1969) financed by the U.S. Department of Defense
First Email Sent
1971, by Ray Tomlinson
World Wide Web invented by
Tim Berners-Lee in 1989, launched publicly in 1991
First Search Engine
Archie (1990)
First Web Browser
WorldWideWeb (later renamed Nexus)
Wi-Fi Standard Introduced
1997 (IEEE 802.11)
Bluetooth Founded
1994 by Ericsson
5G Internet Launch (India)
October 2022
Why Computer Networks Are Important?
Faster communication
Resource sharing
File/data sharing
Centralized data management
Supports e-commerce & cloud
Types of Computer Networks
Type
Full Form
Coverage
Example
PAN
Personal Area Network
1–10 meters
Bluetooth, smartwatch
LAN
Local Area Network
Building/campus
School lab network
MAN
Metropolitan Area Network
City range
Cable TV networks
WAN
Wide Area Network
Country/worldwide
Internet
SAN
Storage Area Network
High-speed storage access
Data centers
VPN
Virtual Private Network
Secure private network over internet
Office remote access
🔹 Network Topologies
Topology refers to the physical or logical structure of a network.
Topology
Features
Pros
Cons
Bus
Single cable connecting all devices
Simple, cheap
Single point failure
Star
All nodes connect to a central switch/hub
Reliable, easy troubleshooting
Hub failure affects all
Ring
Devices connected in a loop
Equal access
One failure disrupts network
Mesh
Every device connected to every other
Highly reliable
Expensive
Hybrid
Combination of topologies
Flexible
Complex design
Transmission Media (Communication Channels)
Wired Media
Twisted Pair (UTP/STP) → used in LAN, Ethernet
Coaxial Cable → cable TV
Fiber Optic Cable → fastest, long distance, uses light signals
Wireless Media
Radio waves
Microwaves
Infrared
Satellite (VSAT)
Wi-Fi, Bluetooth, NFC, Mobile networks (2G, 3G, 4G, 5G)
Switching Techniques
Type
Meaning
Circuit Switching
Dedicated link between sender and receiver (used in telephone systems)
Packet Switching
Data is broken into packets; used in internet
Message Switching
Message sent as a whole through intermediate nodes
Important Networking Devices
Device
Function
Modem
Converts digital signals ↔ analog signals
Hub
Broadcasts data to all devices
Switch
Sends data to the intended receiver (efficient hub)
Router
Connects multiple networks; guides data paths
Gateway
Connects networks using different protocols
Repeater
Boosts/extends signal
Bridge
Connects two similar LANs
Internet Protocol Suite
Layer Model
Developed
OSI Model (7 Layers)
1970s – ISO
TCP/IP Model (4 Layers)
1974
OSI Layers (Top to Bottom)
Application
Presentation
Session
Transport
Network
Data Link
Physical
Mnemonic: “Please Do Not Throw Sausage Pizza Away.”
🔹 Important Protocols
Protocol
Purpose
HTTP/HTTPS
Web browsing
FTP/SFTP
File transfer
SMTP / POP3 / IMAP
Email communication
TCP
Reliable communication
UDP
Faster but unreliable communication
IP
Routing packets
DNS
Converts domain names to IP addresses
🔹 Network Security Basics
Firewall
Antivirus
Encryption
Authentication (Username/Password, Biometrics)
VPN
Digital Certificates & SSL
Common Threats: Virus, Worms, Malware, Phishing, Trojan, Ransomware, DDoS attack.
🔹 Wireless Generations Timeline (Important)
Generation
Release
Feature Highlights
1G
1980s
Analog voice
2G
1991
SMS, digital
3G
2001
Internet browsing
4G
2010
High-speed broadband
5G
2019+ / India 2022
IoT, very high speed
Short Questions & Answers
Q: What is the full form of LAN? A: Local Area Network.
Q: Who invented the World Wide Web? A: Tim Berners-Lee.
Q: What is the first computer network? A: ARPANET.
Q: Which device directs data between networks? A: Router.
Q: Which protocol is used for secure web browsing? A: HTTPS.
Q: What topology is used in most modern networks? A: Star topology.
Q: Which cable offers the highest speed? A: Fiber optic cable.
Summary Points
Internet began with ARPANET in 1969
Ray Tomlinson sent the first email in 1971
Tim Berners-Lee invented WWW in 1989
NIC, DNS, TCP/IP, routers, switches are backbone technologies
Networks classified as PAN, LAN, MAN, WAN
Secure communication uses encryption, firewall, authentication
Computers are vital electronic devices combining hardware and software, enabling diverse tasks such as data processing, communication, and complex applications across various sectors.
The Bharat Ratna, India’s highest civilian award since 1954, honors exceptional service across various fields, with a maximum of three awards per year.
The content outlines various subjects for J&K UT exams, covering topics in general knowledge, accountancy, statistics, English, economics, science, and computers.
A computer system comprises hardware, software, and peripherals to process data efficiently. It includes various types such as PCs, servers, and mainframes.
