SUB OS

The World's Smoothest Operating System - Built from Scratch

🚀 Overview

SUB OS is a custom operating system built entirely from scratch in just 9 days! Now features disk I/O, user mode execution, multitasking, virtual memory, and system calls.

Current Version: Alpha v0.9.0
Development Started: November 11, 2025
Current Day: 9 of 365
Progress: ~22% complete
Status: All core systems + disk I/O working! ✅

✨ Features

Fully Implemented (Day 1-9)

Boot & Protection:

• ✅ Custom bootloader
• ✅ Protected Mode (32-bit)
• ✅ GDT with Ring 0/3
• ✅ IDT (256 gates)

Drivers:

• ✅ VGA Text Mode (80x25)
• ✅ PS/2 Keyboard (buffered)
• ✅ PIT Timer (100 Hz)
• ✅ ATA/IDE Disk Driver (PIO mode) 🆕

Memory Management:

• ✅ E820 detection
• ✅ Physical Memory Manager
• ✅ Virtual Memory (paging)
• ✅ Heap allocator

Process Management:

• ✅ PCB
• ✅ Round-robin scheduler
• ✅ Task switching
• ✅ Kernel & user processes

System Interface:

• ✅ System calls (INT 0x80)
• ✅ User mode (Ring 3)
• ✅ TSS

Storage:

• ✅ ATA device detection
• ✅ Sector read/write
• ✅ LBA28 addressing (128GB)
• ✅ Up to 4 drives support

🔨 CI/CD Pipeline

SUB OS uses GitHub Actions for continuous integration:

• Build Workflow: Automatically compiles the OS on every push
• Test Workflow: Validates compilation, binary sizes, and boot tests
• QEMU Testing: Boots OS in emulator to verify functionality
• Artifacts: Successfully built OS images available for download

Build Status

Click the badges above to see latest build results. The CI pipeline:

1. ✅ Compiles bootloader (NASM)
2. ✅ Compiles all kernel modules (GCC)
3. ✅ Links kernel binary
4. ✅ Creates final OS image
5. ✅ Validates bootloader size ≤ 512 bytes
6. ✅ Boot tests in QEMU
7. ✅ Uploads build artifacts

🛠️ Building

Requirements

• OS: Ubuntu 20.04+ (or compatible Linux)
• Compiler: GCC with 32-bit support
• Assembler: NASM
• Emulator: QEMU (for testing)

Build Commands

# Install dependencies (Ubuntu/Debian)
sudo apt-get install build-essential nasm qemu-system-x86

# Clone and build
git clone https://github.com/subhobhai943/sub-os.git
cd sub-os
make

# Run in QEMU (128MB RAM)
make run

# Debug mode
make debug

# Clean build
make clean

📊 Statistics

• Development Time: 9 days
• Total Files: 54
• Lines of Code: ~7,500
• Commits: 42+
• Major Systems: 27
• Phase 2 Progress: 10%
• CI/CD: Automated testing enabled

🏆 Milestones

Day	Feature	Status
1-2	Bootloader, Protected Mode	✅
3	Interrupts, Drivers	✅
4	Memory Detection, PMM, Heap	✅
5	Virtual Memory (Paging)	✅
6	Processes, Scheduler	✅
7	System Calls	✅
8	User Mode, TSS	✅
9	ATA/IDE Disk Driver	✅
-	CI/CD Pipeline	✅

🎯 What's Next (Day 10+)

• Simple File System (FAT12 or custom)
• VFS layer
• File operations (open, read, write, close)
• Directory management
• Simple shell

📝 License

MIT License

👨‍💻 Author

Subhobhai
PCMB student from West Bengal

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Status: Day 9 Complete - Disk I/O + CI/CD Working! 💾⚙️🚀

Achievement: Built a complete OS with disk I/O and automated testing in 9 days!