1. What Is an Operating System?

An Operating System (OS) is a system software that acts as an intermediary between a computer's hardware and the user or application programs.

It controls:

• Hardware components (CPU, memory, disk, etc.)

• Software execution

• User interface

Examples: Windows, macOS, Linux, Android, iOS.

2. Booting the OS (Startup Process)

When you power on your computer:

1. BIOS/UEFI runs (Basic Input/Output System or Unified Extensible Firmware Interface).

2. BIOS/UEFI loads the bootloader from disk.

3. The bootloader loads the kernel (core part of the OS) into memory.

4. Kernel initializes hardware, sets up memory, and starts system processes.

 3. Major Functions of an Operating System

a. Process Management

• Handles creating, scheduling, and terminating processes (running programs).

• Ensures efficient use of CPU and prevents conflicts.

b. Memory Management

• Allocates and manages RAM for active processes.

• Handles virtual memory (swap files, paging).

c. File System Management

• Organizes data in files and directories.

• Controls access to files and manages storage devices.

d. Device Management

• Controls input/output devices (keyboard, mouse, printer, etc.) through device drivers.

• Provides a uniform interface for device access.

e. User Interface

• Offers CLI (Command-Line Interface) or GUI (Graphical User Interface).

• Lets users interact with the system and applications.

f. Security & Access Control

• Manages user accounts and permissions.

• Protects system from unauthorized access and malware.

g. Networking

• Supports communication over networks (TCP/IP protocols).

• Enables file sharing, internet access, etc.

 4. Types of Operating Systems

5. Components of an Operating System

6. Common Operating System Services

• Program execution

• I/O operations

• File operations

• Communication (Inter-process Communication)

• Error detection & debugging

• Resource allocation

 7. How Users Interact with the OS

• Via Graphical User Interface (GUI) – like Windows or macOS

• Or via Command Line Interface (CLI) – like Linux terminal, Windows CMD

 8. Modern Trends in OS Design

• Cloud OS: Lightweight systems for accessing cloud services.

• Virtualization Support: Running multiple OS instances (VMs).

• Containerization: Lightweight app environments (e.g., Docker).

• Security enhancements: Sandboxing, encryption, access control.