/Operating-System-Tasks

Primary LanguageC++

Memory Allocator and Disk Scheduler Simulation

A C++ implementation of memory management strategies and disk scheduling algorithms. The project includes a Memory Allocator simulating First Fit, Best Fit, and Worst Fit allocation algorithms, and a Disk Scheduler implementing FCFS, SCAN, and CSCAN disk scheduling algorithms in a 32-bit system with paged memory.

Key Features

Memory Allocator

  • Allocation Strategies
    • First Fit (F): Allocates first available space matching request size
    • Best Fit (B): Finds smallest sufficient free block
    • Worst Fit (W): Uses largest available free space
  • Memory Operations
    • Process allocation/deallocation
    • Memory compaction (defragmentation)
    • Real-time status visualization
  • CLI Interface with familiar OS-style commands

Disk Scheduler

  • Scheduling Algorithms
    • FCFS (First-Come-First-Serve): Processes requests in order of arrival
    • SCAN: Moves head in one direction, servicing requests, then reverses
    • CSCAN: Circular SCAN, services requests in one direction, then jumps to start
  • Performance Metrics
    • Total head movement in cylinders
    • Seek time calculation (assuming 0.1 ms per track)
    • Request order visualization

System Requirements

  • C++17 compiler (g++ recommended)
  • Build-essential tools
  • Unix-like OS or Windows Subsystem for Linux (WSL)

Quick Start

Memory Allocator

  1. Compile

    g++ -std=c++17 Memory_Allocator.cpp -o allocator

  2. Run (Specify total memory in bytes)

    ./allocator 1073741824

    (Launches with 1GB simulated memory)

Disk Scheduler

  1. Compile

    g++ -std=c++17 Disk_Scheduler.cpp -o scheduler

  2. Run

    ./scheduler

    (Prompts for number of tracks, queue size, initial head position, and requests)

Commands (Memory Allocator)

  • RQ <process_name> <size> <allocation_strategy>
    • Request memory allocation
    • Allocation strategies:
      • F: First Fit
      • B: Best Fit
      • W: Worst Fit
  • RL <process_name>: Release memory for a specific process
  • C: Compact memory
  • STAT: Display memory status
  • X: Exit the program

Allocation Example

allocator> RQ Chrome 524288 B 
allocator> STAT
allocator> RL Chrome
allocator> C
allocator> X

Allocates 512KB for "Chrome" using Best Fit strategy

Usage (Disk Scheduler)

  • Input the number of tracks, queue size, and initial head position
  • Enter the track requests
  • Outputs results for FCFS, SCAN, and CSCAN algorithms, including:
    • Total head movement
    • Seek time (0.1 ms per track)
    • Order of serviced requests

Example Run

Enter the number of tracks: 200
Enter the queue size: 8
Enter the initial head: 50
Enter the requests: 82 170 43 140 24 16 190 120

Technical Details

Memory Allocator

  • Memory Structure
    • 4KB page size (4096 bytes)
    • 32-bit address space
    • 4-byte memory cell granularity
    • Contiguous allocation model
  • Algorithm Behavior
    • First Fit: Fast allocation, potential external fragmentation
    • Best Fit: Space-efficient, higher search overhead
    • Worst Fit: Reduces small fragments, best for large allocations

Disk Scheduler

  • Disk Structure
    • Configurable number of tracks
    • Integer-based track requests
    • Head movement measured in cylinders
  • Algorithm Behavior
    • FCFS: Simple, may cause excessive head movement
    • SCAN: Efficient for bidirectional access, reduces starvation
    • CSCAN: Optimized for circular access, minimizes head movement

Implementation Highlights

  • Dynamic memory tracking using C++ STL containers (Memory Allocator)
  • Support for multiple concurrent processes (Memory Allocator)
  • Flexible allocation strategy selection (Memory Allocator)
  • Efficient memory compaction mechanism (Memory Allocator)
  • Accurate head movement and seek time calculations (Disk Scheduler)
  • Sorted request handling for SCAN and CSCAN (Disk Scheduler)
  • Clear visualization of request order (Disk Scheduler)