FCFS,Paging,Mutex,Directories,Drivers

Operating Systems

Master the core concepts that power modern computing systems

What are Operating Systems?

An Operating System (OS) is system 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, making the system convenient and efficient to use.

Think of an operating system as the conductor of an orchestra, coordinating all the different components of your computer to work together harmoniously. It manages processes, memory, files, and input/output operations while ensuring security and resource allocation.

Understanding operating systems is crucial for computer science students and professionals as it provides insights into how computers work at a fundamental level and how to write efficient, system-aware applications.

Real-World Examples

Multitasking

Operating systems use CPU scheduling to run multiple programs simultaneously, switching between them rapidly.

Memory Management

OS manages virtual memory to allow programs to use more memory than physically available through paging.

File Systems

Operating systems organize and manage files and directories on storage devices efficiently.

Security

OS provides access control and user authentication to protect system resources and data.

Device Management

Operating systems manage hardware devices through device drivers and I/O operations.

Process Synchronization

OS coordinates concurrent processes using semaphores, mutexes, and other synchronization mechanisms.

Operating System Concepts

Explore different operating system topics and their implementations

CPU Scheduling Algorithms

First Come First Serve (FCFS)

The simplest CPU scheduling algorithm where processes are executed in the order they arrive in the ready queue.

Non-preemptive Simple Implementation FIFO Order

Shortest Job First (SJF)

Schedules processes based on their burst time, with the shortest job executed first to minimize average waiting time.

Optimal Average WT Non-preemptive Starvation Possible

Shortest Remaining Time First (SRTF)

Preemptive version of SJF where the process with shortest remaining time gets CPU priority.

Preemptive Optimal Preemptive Context Switching

Round Robin (RR)

Time-sharing algorithm where each process gets a fixed time quantum in circular order, ensuring fairness.

Preemptive Time Quantum Fair Scheduling

Priority Scheduling

Processes are scheduled based on priority levels, with higher priority processes executed first.

Priority Based Preemptive/Non-preemptive Aging Solution

Multilevel Queue

Processes are divided into multiple queues based on process type, each with its own scheduling algorithm.

Multiple Queues Process Classification Fixed Priority

Memory Management

Paging

Memory management scheme that eliminates external fragmentation by dividing memory into fixed-size pages.

Fixed Size Pages No External Fragmentation Page Table

Segmentation

Memory management technique that divides memory into variable-size segments based on logical divisions.

Variable Size Logical Division Segment Table

Virtual Memory

Technique that allows execution of processes that may not be completely in memory, using demand paging.

Demand Paging Page Replacement Thrashing

Memory Allocation Strategies

Learn about first-fit, best-fit, and worst-fit allocation algorithms. Understand internal and external fragmentation.

First-Fit Best-Fit Worst-Fit

Page Replacement Algorithms

Explore FIFO, LRU, and OPT page replacement algorithms. Understand Belady's anomaly and working set model.

FIFO LRU OPT

Memory Protection & Security

Understand memory protection mechanisms, address binding, and security vulnerabilities in memory management.

Address Binding Protection Keys Buffer Overflow

Process Synchronization

Semaphores

Synchronization primitive that uses a counter to control access to shared resources in concurrent systems.

Binary/Counting Wait/Signal Mutual Exclusion

Mutex (Mutual Exclusion)

Locking mechanism that ensures only one thread can access a critical section at a time.

Binary Lock Ownership Critical Section

Deadlock Detection & Prevention

Techniques to detect, prevent, and resolve deadlocks in systems with multiple processes and resources.

Resource Allocation Wait-for Graph Banker's Algorithm

Reader-Writer Problem

Classic synchronization problem that requires different access patterns for readers and writers to shared data.

Shared Reads Exclusive Writes Priority Solutions

Producer-Consumer Problem

Fundamental synchronization problem involving coordination between processes that produce and consume data.

Buffer Management Synchronization Bounded Buffer

File Systems

File Allocation Methods

Different strategies for allocating disk space to files including contiguous, linked, and indexed allocation.

Contiguous Linked Indexed

Disk Scheduling Algorithms

Algorithms to optimize disk access time including FCFS, SSTF, SCAN, C-SCAN, and LOOK algorithms.

Seek Time SCAN/C-SCAN Optimization

Directory Structure

Organization of files and directories in file systems including single-level, two-level, and hierarchical structures.

Hierarchical Path Resolution File Organization

File Protection & Security

Access control mechanisms, authentication, and encryption techniques to protect files and directories.

Access Control Permissions Encryption

File System Implementation

Learn about in-memory and on-disk structures, buffer management, and caching strategies for efficient file operations.

Inode Structure Buffer Cache Journaling

I/O Systems & Device Management

Device drivers, interrupt handling, and I/O scheduling techniques for efficient hardware communication.

Device Drivers Interrupt Handling I/O Scheduling