Block 1: Operating System Fundamentals

Unit 1: Introduction to Operating Systems

What is an Operating System?

An Operating System (OS) is system software that manages computer hardware resources and provides common services for computer programs. It acts as an intermediary between applications and hardware.

Key Functions:

• Resource Management: CPU, memory, I/O devices
• Process Management: Creation, scheduling, termination
• Memory Management: Allocation, protection, virtual memory
• File Management: Storage, organization, security
• Security: User authentication, access control

Types of Operating Systems

• Batch OS: Jobs processed in batches without user interaction
• Interactive OS: Real-time user interaction with system
• Multiprogramming OS: Multiple programs in memory simultaneously
• Multiprocessing OS: Multiple CPUs working together
• Distributed OS: Multiple computers working as single system
• Real-time OS: Time-critical applications with strict deadlines

Operating System Services

• Program Execution: Loading and running programs
• I/O Operations: Managing input/output devices
• File System Manipulation: File creation, deletion, modification
• Communications: Inter-process communication
• Error Detection: Hardware and software error handling
• Protection: System security and access control

Block 2: Process Management

Unit 2: Process Concepts and Management

Process Concepts

Process: A program in execution consisting of program code, current activity, program counter, and system resources.

Process States:

• New: Process being created
• Ready: Waiting for CPU assignment
• Running: Currently executing on CPU
• Waiting: Blocked for I/O or event completion
• Terminated: Process finished execution

Process Control Block (PCB)

Data structure containing process information:

• Process ID and parent process ID
• Process state and priority
• CPU registers and program counter
• Memory management information
• I/O status information
• Accounting information

Unit 3: CPU Scheduling

Scheduling Algorithms

First-Come, First-Served (FCFS):

• Simple, non-preemptive algorithm
• Processes served in arrival order
• May cause convoy effect

Shortest Job First (SJF):

• Minimizes average waiting time
• Can be preemptive or non-preemptive
• Difficult to predict burst time

Round Robin (RR):

• Time-sharing algorithm with time quantum
• Fair CPU allocation to all processes
• Performance depends on quantum size

Priority Scheduling:

• Processes assigned priority values
• Higher priority processes executed first
• May cause starvation of low-priority processes

Process Synchronization

Critical Section Problem:

• Section of code accessing shared resources
• Mutual exclusion requirement
• Progress and bounded waiting conditions

Synchronization Tools:

• Semaphores: Integer variable for synchronization
• Mutexes: Binary semaphores for mutual exclusion
• Monitors: High-level synchronization construct
• Condition Variables: Waiting for specific conditions

Deadlocks

Deadlock Conditions:

• Mutual Exclusion: Resources cannot be shared
• Hold and Wait: Process holding resources while waiting
• No Preemption: Resources cannot be forcibly taken
• Circular Wait: Circular chain of waiting processes

Deadlock Handling:

• Prevention: Eliminate one of the four conditions
• Avoidance: Dynamic analysis using Banker's algorithm
• Detection: Periodic deadlock detection
• Recovery: Process termination or resource preemption

Block 3: Memory Management

Unit 4: Memory Management Concepts

Memory Hierarchy

• Registers: Fastest, smallest capacity
• Cache Memory: High-speed buffer memory
• Main Memory (RAM): Primary working memory
• Secondary Storage: Hard disks, SSDs

Memory Allocation Strategies

Contiguous Allocation:

• Fixed Partitioning: Memory divided into fixed-size partitions
• Dynamic Partitioning: Partitions created as needed
• Buddy System: Power-of-2 allocation strategy

Non-Contiguous Allocation:

• Paging: Fixed-size pages and frames
• Segmentation: Variable-size logical segments
• Segmented Paging: Combination of both approaches

Unit 5: Virtual Memory

Virtual Memory Concepts

Virtual memory allows execution of programs larger than physical memory by using secondary storage as extension of main memory.

Benefits:

• Larger address space than physical memory
• Better multiprogramming performance
• Protection between processes
• Shared memory between processes

Page Replacement Algorithms

• FIFO (First-In-First-Out): Replace oldest page
• LRU (Least Recently Used): Replace least recently accessed page
• Optimal: Replace page that won't be used for longest time
• Clock Algorithm: Circular list with reference bit

Thrashing

Phenomenon where system spends more time swapping pages than executing processes due to insufficient memory.

Solutions:

• Increase physical memory
• Reduce multiprogramming level
• Use working set model
• Implement page fault frequency algorithm

Block 4: File Systems

Unit 6: File System Concepts

File Concepts

A file is a named collection of related information stored on secondary storage.

File Attributes:

• Name: Symbolic file identifier
• Type: File format and content type
• Location: Physical storage location
• Size: Current file size in bytes
• Protection: Access permissions
• Time/Date: Creation, modification, access times

File Operations

• Create: Make new file entry
• Write: Add data to file
• Read: Retrieve data from file
• Seek: Position file pointer
• Delete: Remove file from system
• Truncate: Reduce file size

Directory Structure

• Single-Level: All files in one directory
• Two-Level: Separate directory for each user
• Tree-Structured: Hierarchical directory organization
• Acyclic Graph: Shared subdirectories allowed
• General Graph: Links and cycles permitted

Unit 7: File System Implementation

File Allocation Methods

Contiguous Allocation:

• Files stored in consecutive disk blocks
• Simple and fast access
• External fragmentation problem

Linked Allocation:

• Each block contains pointer to next block
• No external fragmentation
• Sequential access only

Indexed Allocation:

• Index block contains pointers to data blocks
• Direct access to any block
• Index overhead for small files

Popular File Systems

FAT File System:

• File Allocation Table stores cluster chain
• FAT16: 2GB partition limit
• FAT32: 2TB partition limit, 4GB file limit

NTFS (New Technology File System):

• Advanced security with ACLs
• File compression and encryption
• Journaling for reliability
• Large file and volume support

ext File Systems (Linux):

• ext2: Standard Linux file system
• ext3: Journaling capability added
• ext4: Enhanced performance and features

Block 5: Networking Fundamentals

Unit 8: Network Concepts

Network Types

• LAN (Local Area Network): Limited geographical area
• MAN (Metropolitan Area Network): City-wide coverage
• WAN (Wide Area Network): Large geographical area
• PAN (Personal Area Network): Personal device connectivity

Network Topologies

• Bus Topology: Single communication line
• Star Topology: Central hub connectivity
• Ring Topology: Circular connection pattern
• Mesh Topology: Multiple interconnections
• Tree Topology: Hierarchical structure

Unit 9: OSI Reference Model

Seven Layers of OSI Model

Layer 1 - Physical Layer:

• Transmission of raw bits over physical medium
• Electrical, mechanical, and procedural specifications
• Examples: Cables, hubs, repeaters

Layer 2 - Data Link Layer:

• Frame synchronization and error detection
• MAC addressing for local delivery
• Examples: Ethernet, Wi-Fi, switches

Layer 3 - Network Layer:

• Routing and logical addressing
• IP addressing and packet forwarding
• Examples: IP, ICMP, routers

Layer 4 - Transport Layer:

• End-to-end delivery and error recovery
• Port addressing and flow control
• Examples: TCP, UDP

Layer 5 - Session Layer:

• Session establishment and management
• Dialog control and synchronization
• Examples: NetBIOS, SQL sessions

Layer 6 - Presentation Layer:

• Data formatting and encryption
• Character encoding and compression
• Examples: SSL/TLS, JPEG, MPEG

Layer 7 - Application Layer:

• End-user services and applications
• Network process to application
• Examples: HTTP, FTP, SMTP, DNS

Block 6: Network Protocols and Services

Unit 10: TCP/IP Protocol Suite

Internet Protocol (IP)

IPv4 Features:

• 32-bit addressing (4.3 billion addresses)
• Classful addressing (A, B, C, D, E)
• Subnet masking for network division
• CIDR notation for efficient addressing

IPv6 Features:

• 128-bit addressing (340 undecillion addresses)
• Improved header format
• Built-in security features
• Auto-configuration capabilities

Transport Layer Protocols

TCP (Transmission Control Protocol):

• Connection-oriented, reliable protocol
• Three-way handshake for connection establishment
• Error detection and retransmission
• Flow control and congestion control

UDP (User Datagram Protocol):

• Connectionless, unreliable protocol
• Minimal overhead and fast delivery
• No error recovery or flow control
• Suitable for real-time applications

Unit 11: Application Layer Protocols

Common Application Protocols

HTTP/HTTPS (HyperText Transfer Protocol):

• Web communication protocol
• Request-response model
• HTTPS adds SSL/TLS encryption
• Stateless protocol

FTP (File Transfer Protocol):

• File upload and download
• Two channels: control and data
• Active and passive modes
• User authentication required

SMTP (Simple Mail Transfer Protocol):

• Email transmission protocol
• Push protocol for sending emails
• Works with POP3/IMAP for retrieval
• Text-based protocol

DNS (Domain Name System):

• Translates domain names to IP addresses
• Hierarchical distributed database
• Caching for improved performance
• Various record types (A, AAAA, MX, CNAME)

DNS Components

• DNS Resolver: Client-side query initiator
• Root Name Servers: Top-level domain servers
• TLD Servers: Top-level domain management
• Authoritative Servers: Domain-specific DNS servers
• DNS Cache: Temporary storage for faster lookup

Block 7: Network Devices and Technologies

Unit 12: Network Hardware

Network Devices

Hub:

• Physical layer device (Layer 1)
• Repeats signals to all connected devices
• Creates single collision domain
• Half-duplex communication

Switch:

• Data link layer device (Layer 2)
• MAC address learning and forwarding
• Separate collision domain per port
• Full-duplex communication

Router:

• Network layer device (Layer 3)
• IP address-based routing decisions
• Connects different network segments
• Implements routing protocols

Bridge:

• Data link layer device (Layer 2)
• Connects similar network segments
• MAC address-based forwarding
• Reduces collision domains

Gateway:

• Application layer device (Layer 7)
• Protocol conversion between networks
• Connects networks with different protocols
• Complete packet translation

Unit 13: Network Technologies

Ethernet Technology

Ethernet Standards:

• 10BASE-T: 10 Mbps over twisted pair
• 100BASE-TX: 100 Mbps Fast Ethernet
• 1000BASE-T: 1 Gbps Gigabit Ethernet
• 10GBASE-T: 10 Gbps over copper

CSMA/CD Protocol:

• Carrier Sense Multiple Access with Collision Detection
• Listen before transmitting
• Detect collisions during transmission
• Exponential backoff algorithm

Wireless Technologies

Wi-Fi Standards:

• 802.11a: 54 Mbps at 5 GHz
• 802.11b: 11 Mbps at 2.4 GHz
• 802.11g: 54 Mbps at 2.4 GHz
• 802.11n: 300+ Mbps with MIMO
• 802.11ac: Gigabit speeds at 5 GHz

Wireless Security:

• WEP: Weak encryption protocol
• WPA: Improved security with TKIP
• WPA2: Strong AES encryption
• WPA3: Latest security standard

Block 8: Network Security and Management

Unit 14: Network Security

Security Threats

• Unauthorized Access: Gaining illegal system access
• Data Interception: Eavesdropping on communications
• Data Manipulation: Altering transmitted data
• Denial of Service: Preventing legitimate access
• Malware: Viruses, worms, trojans

Security Mechanisms

Firewall:

• Network security barrier
• Packet filtering based on rules
• Stateful inspection capabilities
• Application layer filtering

Intrusion Detection System (IDS):

• Monitors network traffic for suspicious activity
• Signature-based and anomaly-based detection
• Network-based and host-based IDS
• Real-time threat detection

VPN (Virtual Private Network):

• Secure communication over public networks
• Encryption of data in transit
• Remote access and site-to-site connectivity
• Authentication and authorization

Authentication Methods

• Password-based: Username and password combinations
• Token-based: Physical or digital tokens
• Biometric: Fingerprint, retina, voice recognition
• Multi-factor: Combination of authentication methods
• Certificate-based: Digital certificates and PKI

Unit 15: Network Management

Network Management Functions

• Fault Management: Problem detection and resolution
• Configuration Management: Device configuration control
• Performance Management: Monitoring and optimization
• Security Management: Access control and security policies
• Accounting Management: Resource usage tracking

SNMP (Simple Network Management Protocol)

SNMP Components:

• SNMP Manager: Network management station
• SNMP Agent: Software on managed devices
• MIB: Management Information Base
• Network Management System: Centralized management

SNMP Operations:

• GET: Retrieve specific information
• SET: Modify configuration parameters
• TRAP: Unsolicited event notifications
• WALK: Retrieve multiple related objects

Important Commands and Configuration

Linux Networking Commands

# View network interfaces
ip addr show
ifconfig

# Configure IP address
ip addr add 192.168.1.10/24 dev eth0
ifconfig eth0 192.168.1.10 netmask 255.255.255.0

# View routing table
ip route show
route -n

# Add default gateway
ip route add default via 192.168.1.1
route add default gw 192.168.1.1

# Configure DNS servers
echo "nameserver 8.8.8.8" >> /etc/resolv.conf
echo "nameserver 8.8.4.4" >> /etc/resolv.conf

# Test DNS resolution
nslookup google.com
dig google.com
host google.com

# Test connectivity
ping google.com
ping -c 4 192.168.1.1

# Trace route
traceroute google.com
tracepath google.com

# Port scanning
nmap -p 80,443 google.com
netstat -tuln

Windows Networking Commands

# Network configuration
ipconfig /all
ipconfig /release
ipconfig /renew
ipconfig /flushdns

# Network connectivity
ping google.com
tracert google.com
pathping google.com

# Network connections
netstat -an
netstat -r

# ARP table
arp -a

Exam Preparation Tips

Important Topics for Exam

• Operating System Concepts: Process management, memory management, file systems
• CPU Scheduling: Algorithms and their characteristics
• Synchronization: Critical section, semaphores, deadlocks
• Memory Management: Paging, segmentation, virtual memory
• File Systems: FAT, NTFS, allocation methods
• OSI Model: All seven layers and their functions
• TCP/IP: Protocol characteristics and differences
• Network Devices: Router vs bridge vs switch differences
• Network Security: Authentication methods, firewall, VPN
• DNS: Components and configuration

Study Strategy

• Focus on concepts rather than memorization
• Practice diagrams for OSI model and network topologies
• Understand command syntax for Linux and Windows
• Review previous year question papers
• Practice numerical problems in scheduling algorithms
• Create comparison tables for similar concepts