MehdiOS: A MIT Portfolio Operating System

A 32-bit protected mode operating system kernel written from scratch in C and Assembly. This project demonstrates low-level systems programming, memory management, and hardware interaction.

Features Application

Phase 1: Foundation

• Custom Bootloader: 512-byte MBR (Assembly) that switches to 32-bit Protected Mode.
• GDT: Global Descriptor Table for flat memory model.
• VGA Driver: Text mode (80x25) with scrolling and cursor support.
• Serial Debugging: Logs kernel events to COM1 for headless debugging.

Phase 2: Core Features

• Interrupts (IDT): Full Interrupt Descriptor Table handling CPU exceptions (Divide-by-zero, etc.).
• PIC Remapping: Programmable Interrupt Controller remapped to avoid conflicts.
• Keyboard Driver: Interrupt-driven (IRQ1) PS/2 keyboard support.
• Shell: Interactive command-line interface with help, echo, clear.
• Memory Manager: Basic kmalloc placement heap allocator.

Phase 3: Advanced

• ATA Driver: Protected Mode PIO driver to read hard disk sectors.
• File System: FAT12 parsing logic (implemented) and ls/cat commands.

Setup Requirements

Windows Users: Use WSL2 (Ubuntu). See Windows Setup Guide.

# Install Tools (Ubuntu/WSL)
sudo apt update
sudo apt install build-essential nasm qemu-system-x86 gcc-multilib

Building and Running

# Build
make

# Run (QEMU)
make run

# Debug
make debug

Directory Structure

• boot/: Assembly bootloader & GDT.
• kernel/: Core C kernel, Shell, Memory Manager.
• cpu/: Interrupts (IDT, ISR) and Timer.
• drivers/: Hardware drivers (Screen, Keyboard, ATA, Serial).
• fs/: File System logic (FAT12).
• docs/: Architecture documentation & Demo Script.