Introduction to Operating Systems

Introduction to Operating Systems

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

What is an Operating System?

An OS is a collection of software that:

• Manages computer hardware resources
• Provides a platform for application programs
• Acts as an interface between user and hardware
• Controls and coordinates the use of hardware among various applications

Functions of Operating System

1. Process Management

• Creating and deleting processes
• Suspending and resuming processes
• Process synchronization
• Process communication
• Deadlock handling

2. Memory Management

• Keeping track of memory usage
• Allocating and deallocating memory
• Memory protection
• Virtual memory management

3. File System Management

• Creating and deleting files
• Creating and deleting directories
• File manipulation (read, write, modify)
• File backup and recovery

4. Device Management

• Device communication
• Device drivers
• I/O scheduling
• Buffer management

5. Security and Protection

• User authentication
• Access control
• Resource protection
• Security policies

Types of Operating Systems

1. Batch Operating System

• Jobs processed in batches
• No user interaction during execution
• Example: Early mainframe systems

2. Time-Sharing Operating System

• Multiple users share system resources
• CPU time is shared among users
• Example: Unix, Linux

3. Real-Time Operating System (RTOS)

• Time-critical applications
• Guaranteed response time
• Example: VxWorks, QNX

4. Distributed Operating System

• Multiple computers connected via network
• Shared resources across network
• Example: Distributed systems

5. Network Operating System

• Manages network resources
• Provides network services
• Example: Windows Server, Linux Server

6. Mobile Operating System

• Designed for mobile devices
• Touch-based interface
• Example: Android, iOS

Operating System Structure

1. Monolithic Kernel

• All OS services in kernel
• Fast execution
• Less modular
• Example: Linux, Unix

2. Microkernel

• Minimal kernel
• Services run as user processes
• More modular
• Example: QNX, MINIX

3. Hybrid Kernel

• Combination of monolithic and microkernel
• Some services in kernel, some as processes
• Example: Windows, macOS

GATE CS Weightage

Operating Systems typically accounts for:

• 10-14 marks out of 100 in GATE CS
• High priority subject
• Requires conceptual understanding

Important Topics for GATE CS

1. Process Management (High Priority)

• Process scheduling algorithms
• Process synchronization
• Deadlocks

1. Memory Management (High Priority)

• Paging and segmentation
• Virtual memory
• Page replacement algorithms

1. File Systems (Medium Priority)

• File organization
• Directory structures
• Disk scheduling

1. I/O Management (Medium Priority)

• I/O devices
• I/O scheduling
• Device drivers