My-Operating-System-OpenOS

OpenOS Development Roadmap

Current Status (v0.1)

✅ Completed Features:

• Multiboot-compliant bootloader
• 32-bit protected mode kernel
• VGA text mode terminal with scrolling
• Interrupt Descriptor Table (IDT) setup
• Programmable Interrupt Controller (PIC) configuration
• PS/2 keyboard driver with modifier key support
• Interactive shell prompt
• Basic I/O port operations

Phase 1: Core Interrupt System (Current)

Goal: Robust interrupt handling and basic I/O

Completed

• IDT initialization
• PIC remapping
• Keyboard interrupt handler (IRQ1)
• Scan code to ASCII translation
• Shift and Caps Lock support
• Backspace and Enter handling
• Line buffering

Remaining

• Exception handlers (page fault, GPF, divide by zero, etc.)
• Better error reporting for exceptions
• Double fault handler

Phase 2: Timer and Basic Scheduling

Goal: Add time awareness and prepare for multitasking

Tasks

• PIT (Programmable Interval Timer) initialization
• Timer interrupt handler (IRQ0)
• Global tick counter
• Basic delay/sleep functions
• Uptime tracking

Estimated Complexity

• Difficulty: Easy-Medium
• Files to modify: kernel.c, new timer.c/h
• Dependencies: PIC and IDT (already done)

Phase 3: Memory Management

Goal: Proper memory allocation and virtual memory

Physical Memory Manager

• Memory map from bootloader (Multiboot info)
• Bitmap-based physical page allocator
• Page frame allocation/deallocation
• Memory statistics (total, used, free)

Virtual Memory (Paging)

• Page directory and page table structures
• Identity mapping for kernel
• Higher-half kernel mapping (optional)
• Page fault handler
• Virtual address allocation

Kernel Heap

• Simple heap allocator (malloc/free)
• First-fit or best-fit algorithm
• Heap expansion/contraction
• Memory leak detection (debug mode)

Estimated Complexity

• Difficulty: Medium-Hard
• Files: memory.c/h, paging.c/h, heap.c/h
• Critical: Page fault handler is essential

Phase 4: Process Management

Goal: Multiple processes and context switching

Process Abstraction

• struct process with register state
• Process ID allocation
• Process state (ready, running, blocked)
• Process creation/termination
• Process list/queue

Context Switching

• Save/restore CPU registers
• Switch page directories
• Switch stack pointers
• TSS (Task State Segment) setup

Simple Scheduler

• Round-robin scheduling algorithm
• Priority levels (optional)
• Scheduler tick (integrate with timer)
• Idle process

Estimated Complexity

• Difficulty: Hard
• Files: process.c/h, scheduler.c/h, context.S
• Dependencies: Timer, Memory Management

Phase 5: System Calls

Goal: User/kernel mode separation and syscall interface

User Mode Transition

• User mode page tables
• Ring 3 segments in GDT
• Stack switching (kernel/user stacks)
• Privilege level changes

Syscall Interface

• int 0x80 or sysenter mechanism
• Syscall handler
• Syscall table/dispatcher
• Return value handling

Initial Syscalls

• exit() - Process termination
• write() - Output to terminal
• read() - Keyboard input
• fork() - Process creation (advanced)
• exec() - Load program (advanced)

Estimated Complexity

• Difficulty: Medium-Hard
• Files: syscall.c/h, syscall.S, modifications to process.c
• Dependencies: Process Management

Phase 6: Enhanced Shell

Goal: Useful command-line interface

Command Parsing

• Tokenize input (split by spaces)
• Command registry/lookup
• Argument parsing

Built-in Commands

• help - Show available commands
• clear - Clear screen
• echo - Print arguments
• uptime - Show system uptime
• meminfo - Display memory statistics
• ps - List processes
• kill - Terminate process
• reboot - Restart system

Command History

• Store previous commands
• Up/down arrow navigation
• History buffer (circular)

Estimated Complexity

• Difficulty: Easy-Medium
• Files: shell.c/h, commands.c/h

Phase 7: File System (Future)

Goal: Persistent storage and file I/O

Disk Driver

• ATA/IDE PIO mode driver
• Read/write sectors
• Disk detection

File System

• Simple file system (custom or FAT12/16)
• File operations (open, close, read, write)
• Directory operations
• Virtual file system (VFS) layer

Estimated Complexity

• Difficulty: Very Hard
• Files: ata.c/h, fs.c/h, vfs.c/h

Phase 8: Advanced Features (Long-term)

Networking

• NE2000 or RTL8139 network driver
• TCP/IP stack (simplified)
• Sockets interface

Graphics

• VESA VBE framebuffer
• Basic windowing system
• Mouse support

Advanced IPC

• Pipes
• Shared memory
• Message queues

Multi-core Support

• SMP (Symmetric Multiprocessing)
• Per-CPU data structures
• Spinlocks and synchronization

Contributing to the Roadmap

Want to implement a feature? Great!

1. Pick a task from the current or next phase
2. Discuss your approach (open an issue)
3. Implement incrementally (small PRs are better)
4. Test thoroughly (especially with QEMU)
5. Document your changes (code comments + docs)

Difficulty Guide

• Easy: Basic C knowledge, clear instructions
• Medium: Understanding of OS concepts required
• Hard: Deep understanding of x86 architecture
• Very Hard: Extensive research and debugging needed

Learning Resources

For each phase, these resources will help:

General

• OSDev Wiki - Start here
• The little book about OS development
• xv6 Source Code - Great reference

Phase-Specific

• Interrupts: OSDev Interrupts
• Memory: OSDev Paging
• Processes: OSDev Multitasking
• Syscalls: OSDev System Calls

Version History

• v0.1 (Current): Basic interrupt handling and keyboard I/O
• v0.2 (Planned): Exception handlers and timer
• v0.3 (Planned): Memory management
• v0.4 (Planned): Process management and scheduling
• v1.0 (Goal): Full multitasking OS with syscalls and shell

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Last Updated: February 2026

This roadmap is a living document and will evolve as the project grows. Suggestions and contributions are always welcome!

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