Unit II Operating System & File system management | Cse111 Orientation Of Computing | B.tech CSE

What is an Operating System?

An Operating System (OS) is a software layer that acts as an intermediary between computer hardware and the user. It manages hardware resources and provides a set of services for application software, enabling the efficient use of a computer’s resources.

Key Components of an Operating System

Kernel:

• The core part of the OS that manages system resources.
• Handles communication between hardware and software.
• Responsible for process management, memory management, device management, and system calls.

User Interface:

• The interface through which users interact with the OS.
• Can be a Graphical User Interface (GUI) (e.g., Windows, macOS) or a Command-Line Interface (CLI) (e.g., Linux terminal).
• Allows users to execute commands, manage files, and launch applications.

File System:

• Organizes and manages how data is stored and retrieved on storage devices.
• Provides a way to create, delete, read, and write files and directories.
• Different file systems include NTFS (Windows), ext4 (Linux), and HFS+ (macOS).

Device Drivers:

• Specialized software that allows the OS to communicate with hardware devices (printers, graphics cards, etc.).
• Ensures that applications can use hardware without needing to know the specifics of the hardware.

System Libraries:

• Collections of pre-written code that developers can use to perform common tasks.
• Provide standard functions and routines that applications can call.

System Utilities:

• Tools and applications that perform maintenance tasks (e.g., disk management, backup).
• Include antivirus software, disk cleanup tools, and system monitoring applications.

Process Management:

• Responsible for managing processes in the system, including their creation, scheduling, and termination.
• Ensures that multiple processes can run concurrently without interfering with each other.

Memory Management:

• Manages the allocation and deallocation of memory space for processes.
• Keeps track of each byte in a computer’s memory and ensures efficient use of RAM.

Security and Access Control:

• Implements measures to protect system resources from unauthorized access.
• Manages user accounts, permissions, and authentication.

2. Windows Operating System Versions and Features

1. Windows 1.0

• Launch Date: November 1985
• Features: Introduced a graphical user interface (GUI) over MS-DOS, with basic applications like Paint and Notepad.

2. Windows 3.0

• Launch Date: May 1990
• Features: Enhanced GUI, support for virtual memory, improved multitasking, and a more robust file manager.

3. Windows 95

• Launch Date: August 1995
• Features: Introduced the Start menu, taskbar, plug and play hardware support, and improved networking capabilities.

4. Windows 98

• Launch Date: June 1998
• Features: Improved hardware support, Internet Explorer integration, and the introduction of the Quick Launch bar.

5. Windows 2000

• Launch Date: February 2000
• Features: Enhanced stability and security, Active Directory support, and improved networking and file system capabilities.

6. Windows ME (Millennium Edition)

• Launch Date: September 2000
• Features: Focused on home users with enhanced multimedia support, System Restore, and Windows Movie Maker.

7. Windows XP

• Launch Date: October 2001
• Features: Significant UI overhaul, improved performance, better security features, and support for 64-bit processors.

8. Windows Vista

• Launch Date: January 2007
• Features: New Aero interface, enhanced security features (User Account Control), and improved search functionality.

9. Windows 7

• Launch Date: October 2009
• Features: Faster performance, taskbar improvements, better touch support, and enhanced window management (Aero Snap).

10. Windows 8

• Launch Date: October 2012
• Features: Introduced the tile-based Start screen, improved touch support, and integration with cloud services.

11. Windows 8.1

• Launch Date: October 2013
• Features: Addressed user feedback from Windows 8, reintroduced the Start button, and added enhanced multitasking features.

12. Windows 10

• Launch Date: July 2015
• Features: Unified platform for desktops and tablets, Cortana integration, virtual desktops, and a return to a more traditional Start menu.

13. Windows 11

• Launch Date: October 5, 2021
• Features: Redesigned Start menu and taskbar, enhanced gaming features, improved window management (Snap Layouts), and better integration with Microsoft Teams.

Installation Process for Windows OS

1. Preparation

• Check System Requirements: Ensure the hardware meets the minimum requirements for the Windows version being installed.
• Backup Data: Save important files to avoid loss during installation.
• Create Installation Media: Use a USB flash drive or DVD. You can download the Windows Media Creation Tool from Microsoft’s website to create the installation media.

2. Boot from Installation Media

• Insert the Installation Media: Connect the USB drive or insert the DVD.
• Access BIOS/UEFI Settings: Restart the computer and enter BIOS/UEFI (usually by pressing F2, F10, DEL, or ESC during startup).
• Set Boot Order: Change the boot order to prioritize the USB/DVD drive.
• Save and Exit: Save changes and restart the computer.

3. Language and Settings

• Select Language, Time, and Keyboard Layout: Once the installation media loads, choose your preferred language, time format, and keyboard layout.

4. Installation Type

• Click "Install Now": Start the installation process.
• Enter Product Key: If prompted, enter the Windows product key. You can choose to skip this step if you want to enter it later.
• Accept License Terms: Read and accept the Microsoft Software License Terms.

5. Choose Installation Type

• Upgrade: Keeps existing files, settings, and applications. This is typically used when upgrading from a previous version of Windows.
• Custom: A clean installation where you can partition the hard drive, delete existing partitions, or format the drive. Recommended for best performance.

6. Disk Partitioning

• Select Disk for Installation: If doing a custom installation, select the disk or partition where you want to install Windows.
• Create/Delete/Format Partitions: You can manage partitions as needed. Click "Next" after selecting the desired partition.

7. Installation Process

• Copying Files: The installer copies Windows files to the selected partition.
• Installing Features and Updates: This process may take some time as the system installs necessary features and updates.
• Finalizing Installation: The system may restart multiple times during this phase.

8. Configuration

• User Account Setup: Create a user account and set a password. You may also set up a Microsoft account for additional features.
• Privacy Settings: Configure privacy options, such as location services and diagnostic data.
• Network Setup: Connect to a Wi-Fi network or configure Ethernet settings.

9. Finalizing Setup

• Additional Settings: Configure settings like Cortana, OneDrive, and other Microsoft services.
• Desktop Setup: Once the installation is complete, the system will take you to the desktop where you can start using Windows.

Directory Hierarchy of Windows Operating System

Windows uses a hierarchical file system to organize data. There are two main levels:

Single-Level Directory Hierarchy

In a single-level directory structure, all files are stored in one directory without any subdirectories. This approach was common in early operating systems. Here are some characteristics:

• Flat Structure: All files reside in the same directory, making it simple to navigate.
• Limited Scalability: As the number of files increases, it becomes harder to manage and locate specific files.
• Example Use: Early versions of DOS used a single-level directory structure.

 Multiple-Level Directory Hierarchy

The multiple-level directory hierarchy is the standard in modern operating systems, including Windows. It allows for a more organized structure where directories can contain subdirectories, which can, in turn, contain their own subdirectories and files. Key features include:

• Tree Structure: Organized like a tree, with a root directory and multiple levels of subdirectories.
• Improved Organization: Allows for grouping files logically, making it easier to manage large numbers of files.
• Access Control: Permissions can be set at various levels for different users.
• Components:
• Root Directory: The top-level directory (e.g., C:\).
• Subdirectories: Folders within the root that can contain files and additional subdirectories.

Key Points:

• Ease of Navigation: Users can easily navigate through directories and subdirectories to find files.
• File Organization: Related files can be stored together in specific folders, reducing clutter.
• Multiple Access Levels: Different users can have different permissions on various directories.

Bootloader Overview

Definition: A bootloader is a small program that initializes hardware and loads the operating system (OS) into memory when the computer starts.

Key Functions:

• System Initialization: Checks and initializes hardware components (POST).
• Finds the OS: Locates the operating system on the storage device.
• Loads the Kernel: Loads the OS kernel into memory.
• Transfers Control: Hands over control to the OS for further initialization.
• Provides Boot Options: Offers a menu for selecting between multiple operating systems (if applicable).

Components:

• Boot Sector: The first sector on a storage device containing the bootloader code.
• Boot Configuration Data (BCD): Stores boot settings for Windows systems.
• Boot Menu: Displays available OS options to the user.

Booting Process Steps:

• Power On: System powers up and BIOS/UEFI initializes hardware.
• POST: Performs hardware checks.
• Locating Bootloader: BIOS/UEFI finds the bootable device.
• Executing Bootloader: Loads and runs the bootloader from the boot sector.
• Loading the Kernel: Bootloader loads the OS kernel into memory.
• Transferring Control: Hands over control to the OS.

File System Basics

Definition: A file system is a method and data structure that an operating system uses to manage files on a storage device. It defines how data is stored, organized, retrieved, and managed.

Key Functions:

• File Naming: Specifies rules for naming files (e.g., length, allowed characters).
• Storage Allocation: Manages how disk space is allocated to files.
• Directory Structure: Organizes files into directories (folders) for easier access.
• Access Control: Manages permissions to ensure security and integrity.

Types of File Systems

1. FAT12

• Introduced: 1980
• Table Size: 12-bit
• Max Volume Size: Up to 32 MB
• Max File Size: 32 MB
• Cluster Size: Up to 4 KB
• Use Cases: Primarily for floppy disks and embedded systems.

2. FAT16

• Introduced: 1984
• Table Size: 16-bit
• Max Volume Size: Up to 2 GB
• Max File Size: 2 GB
• Cluster Size: 2 KB to 32 KB
• Use Cases: Used in DOS, early Windows versions, and some memory cards.

3. FAT32

• Introduced: 1996
• Table Size: 32-bit
• Max Volume Size: Up to 2 TB (theoretical limit up to 16 TB)
• Max File Size: 4 GB
• Cluster Size: 512 bytes to 32 KB
• Use Cases: Commonly used in USB drives, memory cards, and external hard drives due to cross-platform compatibility.

Summary

• FAT12: Simple, limited to small disks; mainly for floppy disks.
• FAT16: Improved capacity; used in older systems.
• FAT32: Most versatile; supports larger volumes and files, widely used today.

Feature	FAT12	FAT16	FAT32
Introduced	1980	1984	1996
Table Size	12-bit	16-bit	32-bit
Max Volume Size	Up to 32 MB	Up to 2 GB	Up to 2 TB
Max File Size	32 MB	2 GB	4 GB
Cluster Size	Up to 4 KB	2 KB to 32 KB	512 bytes to 32 KB
Use Cases	Floppy disks, embedded systems	DOS, early Windows	USB drives, memory cards, external HDDs

Pipes and Redirection

Pipes (|)

Definition: Pipes allow you to use the output of one command as the input to another command.

Usage:

• Example: command1 | command2
• Example Command: ls -l | grep "txt"
• This lists files and filters the output to show only those containing "txt".

Redirection

• Output Redirection (> and >>):
• >: Redirects output to a file (overwrites).
• Example: echo "Hello" > file.txt
• >>: Redirects output to a file (appends).
• Example: echo "World" >> file.txt
• Input Redirection (<):
• Takes input from a file instead of the keyboard.
• Example: sort < file.txt

Searching the File System

Using find Command

• Purpose: Searches for files and directories in a specified location.
• Basic Syntax: find [path] [options] [expression]
• Common Examples:
• Find all .txt files: find /path/to/dir -name "*.txt"
• Find files modified in the last 7 days: find /path/to/dir -mtime -7

Using grep Command

• Purpose: Searches for specific patterns within files using regular expressions.
• Basic Syntax: grep [options] pattern [file]
• Common Examples:
• Search for a word in a file: grep "search_term" file.txt
• Search recursively in a directory: grep -r "search_term" /path/to/dir

Simple Regular Expressions with grep

• Basic Patterns:
• . : Matches any single character.
• * : Matches zero or more occurrences of the preceding character.
• ^ : Matches the start of a line.
• $ : Matches the end of a line.
• Examples:
• Match lines starting with "Hello": grep "^Hello" file.txt
• Match lines ending with "world": grep "world$" file.txt
• Match lines containing "abc" anywhere: grep "abc" file.txt

Summary

• Pipes allow chaining commands for efficient processing of data.
• Redirection enables saving command output to files or using file input.
• find helps locate files and directories based on various criteria.
• grep searches for specific text patterns, utilizing simple regular expressions for powerful text processing.

Basic Process Control Using Signals

Signals

• Signals are a form of inter-process communication used to notify processes of events.
• Common signals include:
• SIGINT: Interrupt from the keyboard (Ctrl + C).
• SIGTERM: Termination request.
• SIGSTOP: Stop (pause) a process.
• SIGCONT: Continue a stopped process.

Pausing a Process

• To Pause: Use the SIGSTOP signal.
• Method: Press Ctrl + Z while a foreground process is running.
• Command: kill -STOP <PID> to pause a specific process.

Resuming a Process

• To Resume in Foreground: Use the fg command.
• To Resume in Background: Use the bg command.
• Command to Continue: kill -CONT <PID> to continue a specific paused process.

Example Commands

• Pause a Process:
• In bash
• kill -STOP <PID>
• Resume in Foreground:
• In bash
• fg
• Resume in Background:
• In bash
• bg

Summary

• Use signals like SIGSTOP to pause and SIGCONT to resume processes.
• Ctrl + Z pauses the foreground process, while fg and bg manage resumption in foreground or background.

Terminating a Process

To terminate a process using its PID:

kill <PID>

To forcefully terminate a process:

kill -9 <PID>

To terminate a process by name:

pkill process_name

To kill all processes with a specific name:

killall process_name

Managing the PATH Variable

To view the current PATH variable:

echo $PATH

To add a directory to the PATH:

export PATH=$PATH:/new/directory

To remove a directory from the PATH:

export PATH=$(echo $PATH | sed -e 's|:/directory_to_remove||g' -e 's|/directory_to_remove:||g' -e 's|/directory_to_remove||g')