Operating Systems Chapter Notes | Cyber Olympiad for Class 9 PDF Download

Introduction

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

Functions of an Operating System

• Process Management: Manages the execution of processes, multitasking, and process synchronization.
• Memory Management: Handles memory allocation and deallocation, memory hierarchy, and ensures efficient memory usage.
• File System Management: Manages file storage, organization, retrieval, and access control.
• Device Management: Controls and coordinates the use of hardware devices like printers, disks, etc.
• Security and Access Control: Ensures data security, user authentication, and access control.

Types of Operating Systems

1. Batch Operating Systems
   • Definition: Processes batches of jobs without user interaction.
   • Example: Early mainframe computers.
   • Key Feature: Jobs are processed in bulk.
2. Time-Sharing Operating Systems
   • Definition: Allows multiple users to use the computer simultaneously by sharing time slices.
   • Example: UNIX.
   • Key Feature: Multitasking and multi-user support.
3. Distributed Operating Systems
   • Definition: Manages a group of independent computers and makes them appear as a single computer.
   • Example: LOCUS.
   • Key Feature: Resource sharing across multiple systems.
4. Network Operating Systems
   • Definition: Provides services to computers connected to a network.
   • Example: Windows Server, Linux.
   • Key Feature: File sharing and network resource management.
5. Real-Time Operating Systems (RTOS)
   • Definition: Processes data in real-time with a guaranteed response time.
   • Example: VxWorks.
   • Key Feature: Predictable and timely response.

Components of an Operating System

1. Kernel
   • Definition: Core part of the OS responsible for managing system resources.
   • Functions: Process management, memory management, device management.
2. Shell
   • Definition: Interface that allows users to interact with the kernel.
   • Types: Command-line interface (CLI) and graphical user interface (GUI).
3. File System
   • Definition: Manages files and directories on a storage device.
   • Types: FAT, NTFS, ext3, ext4.

Process Management

1. Process
   • Definition: A program in execution.
   • States: New, Ready, Running, Waiting, Terminated.
2. Scheduling
   • Definition: Determines which process runs at a given time.
   • Types: First-Come, First-Served (FCFS), Shortest Job Next (SJN), Round Robin (RR).

Memory Management

1. Virtual Memory
   • Definition: Simulates more memory than physically available using disk space.
   • Benefits: Allows larger applications to run on systems with limited RAM.
2. Paging
   • Definition: Divides memory into fixed-size pages.
   • Benefits: Efficient memory allocation and management.

File System Management

1. Directory Structure
   • Definition: Organizes files hierarchically.
   • Types: Single-level, two-level, tree-structured.
2. File Permissions
   • Definition: Controls access to files and directories.
   • Types: Read, write, execute.

Device Management

Device Drivers

• Definition: Software that allows the OS to communicate with hardware devices.
• Function: Translates OS commands into device-specific instructions.

Security and Access Control

1. User Authentication
   • Definition: Verifies the identity of a user.
   • Methods: Passwords, biometric scans, multi-factor authentication.
2. Access Control Lists (ACLs)
   • Definition: Defines permissions for files and resources.
   • Benefits: Enhances security by restricting access.

Latest Developments in Operating Systems

• Cloud-Based OS: Operating systems like Chrome OS that leverage cloud computing for enhanced functionality.
• IoT OS: Specialized operating systems designed for Internet of Things (IoT) devices, such as Amazon FreeRTOS and Google Brillo.

Interesting Facts

• Linux Popularity: Linux, an open-source OS, powers most of the world's supercomputers and servers.
• Mobile OS Dominance: Android and iOS are the dominant operating systems in the mobile market, controlling over 99% of the global market share.
• Historical Milestone: The first OS, GM-NAA I/O, was developed in the early 1950s for IBM 704.