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Information & Communication Technologies – Complete Study Notes

IES / ESE PSU

Complete Study Notes for IES ESE Paper I

Ch 1 · Computer Fundamentals Ch 2 · Operating Systems Ch 3 · Networking Ch 4 · Internet & Web Ch 5 · Cybersecurity Ch 6 · Emerging Technologies Quick Revision
1Computer Fundamentals►

A computer is an electronic device that processes data according to instructions (programs). Modern computers are built on the von Neumann architecture with CPU, memory, I/O, and storage as core components.

Generations of Computers

GenerationPeriodTechnologyExample
1st1940–1956Vacuum tubesENIAC, UNIVAC
2nd1956–1963TransistorsIBM 7094
3rd1964–1971Integrated Circuits (ICs)IBM 360
4th1971–presentMicroprocessors (VLSI)Intel 4004, modern PCs
5thPresent+AI, parallel processingAI chips, quantum computers

Number Systems

SystemBaseDigitsConversion
Binary20, 1Multiply by 2ⁿ for positional value
Octal80–7Group binary digits by 3
Decimal100–9Natural number system
Hexadecimal160–9, A–FGroup binary digits by 4
1 byte = 8 bits | 1 KB = 1024 bytes | 1 MB = 1024 KB | 1 GB = 1024 MB | 1 TB = 1024 GB

Computer Architecture — von Neumann Model

  • CPU (Central Processing Unit): ALU (arithmetic/logic) + CU (control unit) + registers
  • Primary Memory: RAM (volatile, read/write), ROM (non-volatile, read only)
  • Secondary Storage: HDD, SSD, optical discs — non-volatile, large capacity
  • I/O devices: Input (keyboard, mouse, scanner), Output (monitor, printer)
  • Bus system: Data bus (transfers data), Address bus (specifies memory location), Control bus (timing/control signals)

CPU Performance

TermDefinition
Clock speedCPU cycles per second (GHz); higher = faster
MIPSMillions of Instructions Per Second
Cache memoryL1 (on-chip, fastest), L2 (on-chip/near chip), L3 (shared) — reduces memory access time
PipelineOverlapping instruction execution stages — fetch, decode, execute, write-back
Multi-coreMultiple CPU cores on single chip for parallel execution

Data Representation

  • ASCII: 7-bit code representing 128 characters (letters, digits, symbols)
  • Unicode/UTF-8: International standard supporting all world scripts
  • 2's complement: Standard representation for signed integers in computers
  • IEEE 754: Standard for floating-point number representation (single: 32-bit, double: 64-bit)
ESE Tip: Know binary-decimal-hex conversions. 2's complement: invert all bits + 1. Example: −5 in 8-bit 2's complement = 11111011.
2Operating Systems►

An Operating System (OS) is system software that manages hardware resources and provides a platform for application programs. It acts as an intermediary between users and hardware.

Functions of an OS

  • Process management (scheduling, multitasking)
  • Memory management (allocation, virtual memory, paging)
  • File system management (directories, permissions, storage)
  • Device management (device drivers, I/O scheduling)
  • Security and access control
  • User interface (CLI/GUI)

Types of Operating Systems

TypeDescriptionExample
Batch OSJobs collected and processed in batches; no user interactionEarly mainframe OS
Time-sharing (Multitasking)Multiple users/processes share CPU time; each gets time sliceUNIX, Linux
Real-time OS (RTOS)Guarantees response within strict time deadlinesVxWorks, FreeRTOS
Distributed OSManages resources across multiple networked computersAmoeba, Plan 9
Mobile OSOptimised for touch, low power, wirelessAndroid, iOS
Network OSManages network resources and servicesWindows Server, Novell

Process Scheduling Algorithms

AlgorithmDescriptionKey Property
FCFSFirst Come First Served — non-preemptiveSimple; convoy effect
SJFShortest Job First — non-preemptiveMinimum average waiting time; starvation possible
Round RobinEach process gets fixed time quantum cyclicallyFair; widely used in time-sharing
PriorityHighest priority process runs firstStarvation of low-priority possible; aging solves it
SRTFShortest Remaining Time First — preemptive SJFOptimal but requires burst time prediction

Memory Management

  • Paging: Physical memory divided into frames; logical memory into pages of same size. No external fragmentation
  • Segmentation: Logical divisions (code, stack, data); variable size. External fragmentation possible
  • Virtual memory: Uses disk as extension of RAM; pages swapped in/out (demand paging)
  • Page replacement: FIFO, LRU (Least Recently Used), Optimal
  • Thrashing: Excessive swapping due to insufficient frames — CPU utilisation drops

File Systems

File SystemOSMax File Size
FAT32Windows (older)4 GB
NTFSWindows16 TB (practical)
ext4Linux16 TB
APFSmacOS/iOSVery large
ESE Tip: Round Robin quantum choice is critical — too small = overhead; too large = becomes FCFS. For context switching overhead the question usually tests: smaller quantum → more context switches → more overhead.
3Computer Networking►

A computer network connects multiple devices to share resources and communicate. Networking is fundamental to the internet, cloud computing, and modern digital infrastructure.

Network Types by Scale

TypeScaleExample
PANPersonal Area Network (~10 m)Bluetooth headset, smartwatch
LANLocal Area Network (building/campus)Office network, home Wi-Fi
MANMetropolitan Area Network (city)City cable network
WANWide Area Network (country/globe)Internet, MPLS networks

OSI Model — 7 Layers

LayerNameFunctionProtocols/Examples
7ApplicationUser interface; network servicesHTTP, FTP, SMTP, DNS
6PresentationData format, encryption, compressionSSL/TLS, JPEG, MPEG
5SessionSession management; checkpointingNetBIOS, RPC
4TransportEnd-to-end reliable delivery; portsTCP, UDP
3NetworkRouting; logical addressing (IP)IP, ICMP, OSPF, BGP
2Data LinkMAC addressing; error detection; framesEthernet, Wi-Fi (802.11), PPP
1PhysicalBit transmission over mediumCables, hubs, repeaters
Mnemonic: "Please Do Not Throw Sausage Pizza Away" (Physical, Data Link, Network, Transport, Session, Presentation, Application)

TCP vs UDP

FeatureTCPUDP
ConnectionConnection-oriented (3-way handshake)Connectionless
ReliabilityGuaranteed delivery, ordering, error-checkingBest effort; no guarantee
SpeedSlower (overhead)Faster
Use casesHTTP, FTP, email, file transferVideo streaming, DNS, VoIP, gaming

IP Addressing

  • IPv4: 32-bit address (4 octets); ~4.3 billion addresses; e.g. 192.168.1.1
  • IPv6: 128-bit address; ~3.4×10³⁸ addresses; e.g. 2001:0db8::1
  • Subnet mask: Distinguishes network and host portions; e.g. 255.255.255.0 = /24
  • Private IP ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
  • NAT: Network Address Translation — maps private IPs to public IP
  • DHCP: Dynamic Host Configuration Protocol — auto-assigns IP addresses
  • DNS: Domain Name System — translates domain names to IP addresses

Network Devices

DeviceOSI LayerFunction
HubLayer 1Broadcasts to all ports; no intelligence
SwitchLayer 2Forwards frames based on MAC address; creates collision domains
RouterLayer 3Routes packets between networks using IP addresses
GatewayLayer 4–7Protocol translation between different networks
FirewallLayer 3–7Filters traffic based on security rules
Access Point (AP)Layer 2Wireless connection to LAN

Wireless Standards

StandardNameMax SpeedFrequency
802.11bWi-Fi 111 Mbps2.4 GHz
802.11gWi-Fi 354 Mbps2.4 GHz
802.11nWi-Fi 4600 Mbps2.4/5 GHz
802.11acWi-Fi 53.5 Gbps5 GHz
802.11axWi-Fi 69.6 Gbps2.4/5/6 GHz
Bluetooth 5.0PAN2 Mbps2.4 GHz
4Internet and Web Technologies►

The Internet is a global network of networks using the TCP/IP protocol suite. The World Wide Web (WWW) is a service running over the internet. Understanding both is essential for IES ICT questions.

Internet History

  • 1969: ARPANET (US DoD) — first packet-switched network
  • 1983: TCP/IP adopted as standard protocol
  • 1991: WWW invented by Tim Berners-Lee at CERN
  • 1993: Mosaic browser — first graphical web browser
  • 2004: Web 2.0 — user-generated content, social media
  • 2010s: Cloud computing, mobile internet, IoT
  • 2020s: Web 3.0, AI-driven internet, metaverse

Internet Protocols

ProtocolPortFunction
HTTP80Web page transfer (HyperText Transfer Protocol)
HTTPS443Secure web (HTTP + TLS encryption)
FTP21File transfer
SFTP22Secure file transfer
SMTP25Send email (Simple Mail Transfer Protocol)
POP3110Receive email (Post Office Protocol)
IMAP143Email access (syncs across devices)
DNS53Domain name resolution
Telnet23Remote terminal (unencrypted)
SSH22Secure remote terminal

Web Technologies

  • HTML: HyperText Markup Language — structure of web pages
  • CSS: Cascading Style Sheets — presentation and layout
  • JavaScript: Client-side scripting — interactivity
  • URL: Uniform Resource Locator — address of a web resource (scheme://host/path)
  • HTTP Methods: GET (retrieve), POST (submit data), PUT (update), DELETE (remove)
  • Cookie: Small data stored on client for session state management
  • Cache: Stored copy of web content for faster re-access

Cloud Computing

ModelFull FormDescriptionExample
IaaSInfrastructure as a ServiceVirtual machines, storage, networkingAWS EC2, Azure VMs
PaaSPlatform as a ServiceDevelopment environment and toolsGoogle App Engine, Heroku
SaaSSoftware as a ServiceReady-to-use applications over internetGmail, Office 365, Salesforce

Deployment Models

  • Public cloud: Resources owned and managed by cloud provider; shared infrastructure
  • Private cloud: Dedicated infrastructure for single organisation; higher security
  • Hybrid cloud: Mix of public and private cloud; flexible workload placement
  • Community cloud: Shared among organisations with common concerns (government, healthcare)
ESE Tip: Know the port numbers — HTTP=80, HTTPS=443, FTP=21, SMTP=25, DNS=53. These are frequently asked. Also know IaaS/PaaS/SaaS hierarchy and examples.
5Cybersecurity►

Cybersecurity protects computer systems and networks from theft, damage, and unauthorised access. With increasing digitalisation of infrastructure, it is critical for engineers to understand security principles.

CIA Triad — Security Objectives

ObjectiveMeaningThreat
ConfidentialityOnly authorised users can access dataEavesdropping, data breach
IntegrityData is accurate and unalteredTampering, man-in-the-middle
AvailabilitySystems and data accessible when neededDoS/DDoS attacks, ransomware

Common Cyber Threats

ThreatDescription
MalwareMalicious software: virus (self-replicating), worm (spreads without host), Trojan (disguised), ransomware (encrypts files for ransom), spyware
PhishingDeceptive emails/websites to steal credentials; spear phishing = targeted
DoS / DDoSDenial of Service / Distributed DoS — floods system to deny legitimate access
SQL InjectionMalicious SQL code inserted into input fields to access database
Cross-site Scripting (XSS)Malicious scripts injected into trusted websites to attack users
Man-in-the-MiddleAttacker intercepts communication between two parties
Zero-day exploitAttack on unknown vulnerability before patch released
Social engineeringManipulating people to reveal information (not technical)

Cryptography

  • Symmetric encryption: Same key for encryption and decryption; fast; AES, DES, 3DES
  • Asymmetric encryption: Public key encrypts; private key decrypts; RSA, ECC
  • Hash function: One-way transformation; SHA-256, MD5 (deprecated for security)
  • Digital signature: Hash of message encrypted with sender's private key — ensures authenticity and integrity
  • SSL/TLS: Secure Sockets Layer / Transport Layer Security — encrypts web traffic (HTTPS)
  • PKI: Public Key Infrastructure — system of digital certificates issued by Certificate Authorities (CA)

Security Measures

MeasureDescription
FirewallFilters network traffic based on rules; packet filtering, stateful, application layer
IDS/IPSIntrusion Detection System (alerts) / Intrusion Prevention System (blocks)
AntivirusDetects and removes malware using signature and heuristic analysis
VPNVirtual Private Network — encrypted tunnel over public network
MFAMulti-Factor Authentication — requires two or more verification factors
Patch managementRegular software updates to fix known vulnerabilities
Backup3-2-1 rule: 3 copies, 2 media types, 1 off-site

Indian Cyber Laws

  • IT Act 2000 (amended 2008): Governs electronic commerce, digital signatures, cyber crimes in India
  • Section 43: Unauthorised access — civil liability (compensation)
  • Section 66: Computer-related offences — criminal liability (imprisonment up to 3 years)
  • Section 66A: (Struck down by Supreme Court 2015 — Shreya Singhal case)
  • Section 67: Publishing obscene material online — up to 5 years imprisonment
  • CERT-In: Computer Emergency Response Team — India's national nodal agency for cybersecurity incidents
  • Digital Personal Data Protection Act 2023 (DPDP): Framework for personal data protection in India
ESE Tip: Know the CIA triad and its threats. AES = symmetric, RSA = asymmetric. IT Act 2000 — Sec 43 (civil), Sec 66 (criminal). CERT-In reports to Ministry of Electronics & IT (MeitY).
6Emerging Technologies in ICT►

Emerging technologies are transforming engineering, governance, and society. IES General Studies tests awareness of these technologies and their applications, implications, and Indian government initiatives.

Artificial Intelligence (AI) and Machine Learning (ML)

  • AI: Simulation of human intelligence by machines — problem solving, reasoning, learning
  • ML: Subset of AI — machines learn from data without being explicitly programmed
  • Deep Learning: Multi-layered neural networks; excels in image/speech recognition
  • Applications: Image recognition, NLP, autonomous vehicles, medical diagnosis, predictive maintenance
  • India AI Mission (2024): ₹10,372 crore — compute infrastructure, AI innovation, responsible AI

Internet of Things (IoT)

  • Network of physical devices embedded with sensors, software, connectivity — collect and exchange data
  • Components: Sensors/actuators, connectivity (Wi-Fi/Bluetooth/5G/LoRa), cloud platform, application
  • Applications: Smart cities, smart grids, precision agriculture, industrial automation (IIoT), healthcare wearables
  • Security concern: Large attack surface; many IoT devices have weak security

Blockchain Technology

  • Distributed ledger where records (blocks) are linked (chained) cryptographically
  • Properties: Decentralised, immutable, transparent, consensus-based
  • Consensus mechanisms: Proof of Work (PoW) — energy intensive; Proof of Stake (PoS) — energy efficient
  • Applications: Cryptocurrency (Bitcoin, Ethereum), land records, supply chain, voting, smart contracts
  • India: National Blockchain Framework (MeitY); land records on blockchain (pilot states)

Big Data

The 5 V's of Big DataMeaning
VolumeMassive scale of data (terabytes to zettabytes)
VelocitySpeed of data generation and processing
VarietyStructured, semi-structured, unstructured data
VeracityAccuracy and trustworthiness of data
ValueInsights derived from data analysis

5G Technology

  • 5th generation mobile network; launched in India 2022
  • Peak speed: 20 Gbps download; latency: <1 ms
  • Enables: massive IoT, autonomous vehicles, smart factories, telemedicine
  • Spectrum bands: sub-6 GHz (coverage) and mmWave (capacity, 26–28 GHz range)

Key India ICT Initiatives

InitiativeYearFocus
Digital India2015Digital infrastructure, e-governance, digital literacy
BharatNet2011Optical fibre broadband to all gram panchayats
UMANG2017Unified Mobile Application for New-age Governance
DigiLocker2015Digital document wallet for citizens
GeM2016Government e-Marketplace for procurement
COWIN2021COVID-19 vaccination management platform
India AI Mission2024AI compute, startups, responsible AI
SemiconIndia2021₹76,000 Cr semiconductor manufacturing incentives
ESE Tip: Digital India launched 2015; BharatNet (formerly National Optical Fibre Network) targets all ~2.5 lakh gram panchayats. Know India's semiconductor push — SemiconIndia programme and fab units.
★Key Facts & Exam Essentials►
TopicKey Fact
1 byte8 bits; 1 KB = 1024 bytes
Computer generations1st: vacuum tubes; 2nd: transistors; 3rd: IC; 4th: microprocessor; 5th: AI
OSI layers7: Application → Presentation → Session → Transport → Network → Data Link → Physical
TCP vs UDPTCP: reliable, connection-oriented; UDP: fast, connectionless
HTTP / HTTPS ports80 / 443
DNS port53
SMTP port25
FTP port21
IPv4 address size32 bits; ~4.3 billion addresses
IPv6 address size128 bits; ~3.4×10³⁸ addresses
AESSymmetric encryption standard
RSAAsymmetric encryption; public/private key pair
SHA-256Cryptographic hash function (256-bit output)
CIA triadConfidentiality, Integrity, Availability
IT Act 2000India's cyber law; Sec 43 (civil), Sec 66 (criminal, up to 3 yr)
CERT-InIndia's cybersecurity incident response body under MeitY
Cloud: IaaS/PaaS/SaaSInfrastructure / Platform / Software as a Service
5G India launch2022; peak 20 Gbps; latency <1 ms
Digital IndiaLaunched 2015; digital infra, e-governance, literacy
BharatNetOptical fibre to all gram panchayats
Big Data 5 V'sVolume, Velocity, Variety, Veracity, Value
BlockchainDecentralised, immutable distributed ledger
WWW inventorTim Berners-Lee, 1991
ARPANET1969; first packet-switched network; precursor to internet