🖥️ FOS Operating System Project 2025

📌 Project Overview

This project is a full implementation of a simplified Operating System as part of the FOS course.

It covers:

• Low-level memory management
• Process scheduling
• Page fault handling
• Synchronization mechanisms
• System calls

The project is divided into Milestones, Group Modules, and Individual Modules to simulate real OS development stages.

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👥 Group Modules (Core System)

🔸 Dynamic Allocator

• Handles dynamic allocation inside heap

• Uses free lists and linked lists

• Supports:

  • alloc_block
  • free_block

• Efficient allocation (O(1) best case)

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🔸 Kernel Heap

• Kernel-level memory management

• Two strategies:

  • Block Allocator (small sizes)
  • Page Allocator (large sizes)

• Uses CUSTOM FIT strategy

• Functions:

  • kmalloc()
  • kfree()
  • Address translation

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🔸 Fault Handler I (Placement)

• Handles page faults (missing pages)
• Loads pages from disk to memory
• Maintains Working Set
• Validates invalid memory access

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👤 Individual Modules (Advanced Features)

🔹 Fault Handler II (Replacement)

• Page replacement algorithms:

  • Optimal (simulation)
  • Clock
  • LRU (Aging)
  • Modified Clock

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🔹 User Heap

• User-level memory allocation

• Lazy allocation (on page fault)

• Uses:

  • Block allocator
  • Page allocator

• Functions:

  • malloc()
  • free()

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🔹 Shared Memory

• Allows processes to share data

• Functions:

  • smalloc()
  • sget()

• Uses reference counting & frame tracking

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🔹 CPU Scheduling

• Priority-based Round Robin Scheduler

• Features:

  • Multiple queues
  • Starvation prevention
  • Dynamic priority handling

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🔹 Kernel Protection

• Synchronization primitives:

  • Sleep Locks
  • Semaphores

• Prevents race conditions

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⚙️ System Architecture

User Programs
     ↓
System Calls
     ↓
Kernel
 ├── Memory Management
 ├── Scheduler
 ├── Synchronization
 └── Page Fault Handler

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📁 Project Structure

FOS_PROJECT_2025_TEMPLATE/
│
├── boot/        # Bootloader
├── kern/        # Kernel code
├── user/        # User programs
├── lib/         # Libraries
├── inc/         # Headers
├── conf/        # Config files
├── obj/         # Build output (ignored)

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🚀 How to Run

make
bochs

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🧪 Testing

The project includes multiple test scenarios for:

• Memory allocation
• Page replacement
• Scheduling
• Synchronization

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⚠️ Important Notes

• Do NOT commit build files (obj/, .o, .asm)
• Always clean before rebuild:

make clean
make

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👥 Team Members

• Bassmala Ezzat
• Fatma Al Zahraa Ahmed
• Bassant Mohamed
• Nouran Mahmoud Mohamed
• Omar Badr
• Omar Gamal

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🏁 Conclusion

This project provides hands-on experience in building core components of an operating system from scratch, including memory management, scheduling, and process synchronization.

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