Lecture 11: Operating Systems
In this lecture, we will study the Operating System (OS), which is the backbone of computer system functionality. The OS is software that manages hardware resources, provides services for application software, and ensures efficient and secure execution of programs.
1. Introduction to Operating Systems
An Operating System is system software that acts as an intermediary between the user, applications, and hardware. It enables users to interact with the computer without needing to know hardware details.
- Examples: Windows, Linux, macOS, Android, iOS, UNIX.
2. Functions of an Operating System
- Process Management: Schedules tasks, handles process creation, execution, and termination.
- Memory Management: Allocates, monitors, and deallocates memory space.
- File System Management: Manages files and directories for storage and retrieval.
- Device Management: Handles communication between hardware and software.
- Security and Protection: Provides authentication, access control, and protection from malware.
- User Interface: Offers CLI (Command-Line Interface) or GUI (Graphical User Interface).
3. Types of Operating Systems
- Batch OS: Executes jobs in batches without user interaction.
- Time-Sharing OS: Allows multiple users to share system resources simultaneously.
- Distributed OS: Manages a group of independent computers as one system.
- Real-Time OS (RTOS): Provides immediate response (used in embedded systems, robotics).
- Network OS: Manages networking and data sharing across connected devices.
- Mobile OS: Designed for mobile devices (Android, iOS).
4. Process Management
A process is a program in execution. The OS manages processes using:
- CPU Scheduling: Decides which process runs when CPU is free (FCFS, SJF, Round Robin).
- Multitasking: Runs multiple processes concurrently.
- Deadlock Handling: Prevents processes from waiting indefinitely for resources.
5. Memory Management
The OS controls how memory is allocated and used:
- Paging: Divides memory into fixed-size pages.
- Segmentation: Divides memory into variable-size segments.
- Virtual Memory: Extends physical memory using disk space.
6. File System Management
The OS provides a structured way to store and retrieve files:
- File creation, deletion, and access control.
- Directory structures (single-level, tree, graph).
- Disk management and storage allocation.
7. Input/Output (I/O) Management
The OS manages communication with peripheral devices:
- Device drivers act as translators between hardware and OS.
- I/O scheduling ensures fair and efficient access to devices.
8. Security and Protection
- User authentication (passwords, biometrics).
- Access control to files and processes.
- Encryption and malware protection.
9. Popular Operating Systems
| OS | Type | Features |
|---|---|---|
| Windows | Desktop/Server | GUI-based, user-friendly, wide software support |
| Linux | Desktop/Server | Open-source, secure, widely used in servers |
| macOS | Desktop | Sleek design, optimized for Apple hardware |
| Android | Mobile | Open-source, customizable, used in most smartphones |
| iOS | Mobile | Secure, optimized for Apple devices |
| UNIX | Server/Workstation | Stable, multiuser, widely used in enterprise environments |
10. Summary
- An Operating System acts as a bridge between hardware, users, and applications.
- Core functions include process, memory, file, and device management.
- Different OS types serve different needs (batch, real-time, distributed, mobile).
- Security is a crucial aspect of modern OS design.
- Examples include Windows, Linux, macOS, Android, and iOS.
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