Operating System Concepts Lecture Notes

Introduction to Operating Systems

• Definition: An operating system (OS) is an intermediary between users and computer hardware.
• Purpose: Provides an environment for executing programs conveniently and efficiently.
• Complexity: Operating systems are large and complex systems.

Components of a Computer System

• Four Main Parts:
  • Hardware
  • Operating System
  • Application Programs
  • Users
• Hardware Components:
  • Central Processing Unit (CPU)
  • Memory
  • Input/Output Devices
• Application Programs: Examples include word processors, spreadsheets, web browsers.
• Function of OS: Controls hardware and coordinates resource usage among various applications and users.

User View of Computer Systems

• User Interface: Many users interact with systems using laptops, PCs, with monitors, keyboards, and mice.
• Resource Utilization: OS designed to maximize work efficiency for individual users.

History and Evolution of Operating Systems

• Early Computing: Originated as military systems for code breaking and plotting.
• 1960 Prediction: Number of transistors on chips would double every 18 months (Moore’s Law).
• Diversity in Operating Systems: Growth in functionality and variety of operating systems available.

Definition and Structure of Operating Systems

• General Definition: OS includes everything that runs when the OS is ordered.
• Kernel: The core program running at all times.
• System Programs: Assist the OS but are not part of the kernel.
• Application Programs: Programs not associated with OS operation.

Interrupts and Device Management

• Function of Interrupts: Signals from device drivers to the CPU when a task is needed.
• Interrupt Service Routines (ISRs): Specialized routines for handling interrupts efficiently.
• Types of Interrupts: Non-maskable and maskable interrupts; prioritization of interrupts is crucial for performance.

Memory Management

• Types of Memory:
  • Main Memory (RAM): Volatile, used for running programs.
  • Non-Volatile Memory: Retains data when power is off (e.g., EEPROM, flash memory).
• Storage Hierarchy:
  • Faster, smaller memory closer to the CPU vs. larger, slower storage (e.g., HDDs, SSDs).

Input/Output Management

• Communication Bus: Common pathway for device communication.
• Direct Memory Access (DMA): Allows devices to transfer data directly to memory without CPU intervention.

Multiprocessor Systems

• Definition: Systems with two or more CPUs sharing resources (memory, I/O).
• Symmetric Multiprocessing (SMP): Each CPU performs all tasks, enhancing efficiency.
• Multicore Processors: Multiple cores on a single chip, impacting OS and application design.

Non-uniform Memory Access (NUMA)

• Definition: Memory architecture allowing CPUs to have local memory, reducing contention.
• Scalability: NUMA systems can accommodate many processors efficiently.

Clustering and High Availability

• Clustered Systems: Groups of individual systems connected via a network for redundancy and high availability.
• Graceful Degradation: Ability to maintain service during component failure.
• Fault Tolerance: Systems designed to withstand failures while continuing operation.
• Parallelization: Running applications concurrently across a cluster to enhance performance.

Conclusion

• Ongoing Developments: Clustering technology rapidly evolving to support high-performance computing and reliability.
• Importance of OS: Operating systems are crucial for managing resources, performance, and providing a user-friendly interface.