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🧠 Roadmap to Build Your Own Operating System (OS)

Creating your own OS is a challenging but highly rewarding project. This guide is designed to take you from zero to a basic functional OS step-by-step.


🧭 Overview of OS Development Phases​


🟒 Phase 1: Preparation & Fundamentals​

🎯 Goal: Understand how an OS works and set up your environment.

  • Learn C (deep dive) and Assembly (x86 basics).
  • Understand boot process: BIOS β†’ Bootloader β†’ Kernel.
  • Learn basic computer architecture (x86/x86_64 or ARM).

Resources:


πŸ› οΈ Phase 2: Setup Environment​

🎯 Goal: Prepare your development and testing environment.

  • Install essential tools:
    • GCC or Clang
    • NASM or GAS
    • QEMU or Bochs
    • GRUB bootloader

Project Structure:

/myos/
β”œβ”€β”€ bootloader/
β”œβ”€β”€ kernel/
└── Makefile

πŸ” Phase 3: Bootloader​

  • 🎯 Goal: Create a bootloader to load your kernel.
  • Write 16-bit real mode boot sector in Assembly.
  • Transition to protected mode or use GRUB to load the kernel.
boot.asm
[bits 16]
org 0x7c00

jmp start
start:
mov ah, 0x0E
mov al, 'H'
int 0x10
jmp $

times 510 - ($ - $$) db 0
dw 0xAA55

🧠 Phase 4: Kernel Development (C + ASM)​

🎯 Goal: Write a simple kernel with a C entry point.

  • Switch to Protected Mode
  • Setup GDT (Global Descriptor Table)
  • Setup IDT (Interrupt Descriptor Table)
  • Handle keyboard & timer interrupts
  • Add a kernel_main() function
void kernel_main() {
printf("Welcome to MyOS!");
while(1);
}

🧩 Phase 5: Core Kernel Features​

🎯 Goal: Implement key OS functionalities.

  • βœ… Memory Management (Physical/Virtual, Paging, Heap)
  • βœ… FileSystem Support (FAT32, EXT2)
  • βœ… Drivers (Keyboard, Display, Disk)
  • βœ… Interrupts & System Calls
  • βœ… Process Scheduler & Multitasking
  • βœ… Basic Shell or TUI (optional)

πŸ§‘β€πŸ’» Phase 6: User Space & Applications​

🎯 Goal: Create a basic CLI with user programs.

  • Setup system call interface
  • Implement ELF binary loader
  • Create shell, calculator, etc.

πŸš€ Phase 7: Advanced Features (Optional)​

🎯 Goal: Take your OS to the next level.

  • Build Networking Stack (TCP/IP)
  • Create GUI with VESA/Framebuffer
  • Add USB, PCIe drivers
  • Multi-core CPU support

πŸ“ Example Project Folder Structure​

/myos
β”œβ”€β”€ bootloader/
β”‚ └── boot.asm
β”œβ”€β”€ kernel/
β”‚ β”œβ”€β”€ kernel.c
β”‚ β”œβ”€β”€ memory.c
β”‚ └── scheduler.c
β”œβ”€β”€ drivers/
β”‚ β”œβ”€β”€ keyboard.c
β”‚ └── video.c
β”œβ”€β”€ include/
β”‚ └── kernel.h
β”œβ”€β”€ lib/
β”‚ └── stdio.c
└── Makefile

  • Tool Purpose
  • NASM Assembly code
  • GCC/Clang Compiling kernel (C)
  • QEMU Emulator for testing
  • GDB Debugger
  • GRUB Bootloader
  • Make/CMake Build system