ArxOS

A 32-bit hobby operating system kernel written from scratch. ArxOS boots via Multiboot bootloader and provides a simple interactive shell environment running in protected mode on x86 hardware.

Status: Early development. Currently boots and runs a basic shell with interrupt handling support. Not UEFI compatible.

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Features

• 32-bit x86 Protected Mode — Runs directly on compatible hardware or emulation
• Multiboot Compatible — Boots via Multiboot-compliant bootloaders (GRUB)
• Interrupt Handling — IDT (Interrupt Descriptor Table) setup with PIC remapping, timer (IRQ0) and keyboard (IRQ1) interrupt support
• Interactive Shell — Command-line interface with basic built-in commands
• VGA Text Mode Output — Direct memory writes to VGA buffer for display
• Keyboard Input — PS/2 keyboard support for user input via interrupts
• Hardware I/O Abstraction — Port I/O utilities for hardware communication

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Architecture

.
├── boot.asm           Bootloader entry point, Multiboot header
├── linker.ld          Linker script for memory layout (1MB entry point)
├── makefile           Build configuration
├── src/
│   ├── kernel.c       Main kernel entry point (kernel_main), timer handler
│   ├── shell.c        Interactive shell with command dispatcher
│   ├── vga.c          VGA text mode driver (80x25 display)
│   ├── keyboard.c     PS/2 keyboard input handler
│   ├── idt.c          IDT initialization and configuration
│   ├── interrupts.asm Assembly stubs for interrupt handlers
│   └── hw_io.c        Hardware port I/O (outb/inb utilities)
├── include/
│   ├── shell.h
│   ├── vga.h
│   ├── keyboard.h
│   ├── idt.h          IDT structures and function declarations
│   └── hw_io.h
└── iso/               GRUB bootable ISO directory (created by `make iso`)

Runtime Flow

1. Boot — boot.asm provides Multiboot header and calls kernel_main()
2. Initialization — Kernel initializes IDT and PIC, clears VGA screen, starts the shell
3. Shell — Displays login prompt (password: 'r'), then command prompt
4. Command Loop — Reads keyboard input via IRQ1, executes built-in commands, repeats
5. Timer — IRQ0 increments timer_ticks counter for system timing

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Building

Requirements

• gcc — 32-bit capable C compiler (gcc -m32)
• as (GNU Assembler) — For x86 assembly (as --32)
• ld (GNU Linker) — With 32-bit support (ld -m elf_i386)
• grub-mkrescue — For creating bootable ISO (optional)
• qemu-system-i386 or qemu-system-x86_64 — For testing (optional)

Compile

make           # Build Arx.bin kernel binary
make clean     # Remove build artifacts

Create Bootable ISO

make iso       # Creates ArxOS.iso with GRUB bootloader

Test in Emulator

# Run kernel directly (Multiboot mode)
make run

# Run ISO in QEMU x86_64 emulator
make run-iso

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Shell Commands

After boot and password entry, the shell accepts:

Command	Description
help	Show available commands
clear	Clear the screen
about	Display OS and kernel version info
ping	Echo "pong" (test command)

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Interrupt Handling

ArxOS implements a basic interrupt handling system:

• IDT (Interrupt Descriptor Table) — 256 entry descriptor table configured in protected mode
• PIC Remapping — Programmable Interrupt Controller remapped to ISA 32-47 for IRQs 0-15
• IRQ0 (Timer) — System timer interrupt, increments timer_ticks counter
• IRQ1 (Keyboard) — PS/2 keyboard interrupt for input handling
• Interrupt Stubs — Assembly stubs (interrupts.asm) handle low-level interrupt dispatch

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Known Limitations

• No UEFI Support — BIOS/Legacy mode only
• Limited Interrupt Support — Only timer (IRQ0) and keyboard (IRQ1) implemented
• No Memory Management — No paging or virtual memory
• Single-threaded — No process/thread scheduling
• No Filesystem — No disk I/O beyond boot
• Minimal Command Set — Basic shell with hardcoded commands

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Learning Resources

This project is educational. Key concepts:

• Bootloaders & Multiboot — How kernels boot and receive control
• x86 Protected Mode — 32-bit CPU mode fundamentals
• Interrupt Handling — IDT setup, PIC configuration, interrupt handlers
• VGA Text Mode — Direct hardware memory access for display
• Hardware Port I/O — Reading/writing to I/O ports
• Linker Scripts — Memory layout and section placement
• Assembly & C Integration — Calling conventions and cross-language boundaries

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Future Ideas

• Extended interrupt handling (exceptions, more IRQs)
• Memory management (paging, heap)
• File system support
• Process/task management
• Expanded command set
• UEFI boot support

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License

GNU GPL v3.0

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Contact

Created by MasterArd. For questions or suggestions, open an issue on GitHub.