SteveOS

SteveOS is a minimal 16-bit x86 operating system built from scratch using Assembly (NASM). It includes a custom bootloader and a simple kernel with a basic command-line interface. The system is packed into a 1.44MB floppy disk image for booting in legacy BIOS environments.

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Features

• FAT12 bootloader written from scratch
• Kernel loaded to 0x1000:0000 in real mode
• Text-based shell with built-in commands:
  • clear, help, info, version, echo, date
• BIOS interrupt-based I/O (INT 10h, INT 13h, INT 16h)
• Sector-based disk reading with retry logic
• Keyboard input with backspace and input buffer handling
• Boots from floppy disk image (steveos.img)
• Fully written in Assembly (NASM)

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Requirements

• NASM (Netwide Assembler)
• GCC (optional, for FAT tool build)
• PowerShell (Windows, used to write to floppy image)
• QEMU, Bochs, or VirtualBox for emulation

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Build Instructions (Windows)

Make sure nasm.exe and gcc.exe are available in your PATH.

1. Build with make

make

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Booting the OS

With QEMU

qemu-system-i386 build\steveos.img

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Notes

• steveos.img is a raw floppy disk image (1.44MB).
• Bootloader resides in sector 0, kernel in sector 1 onward.
• Kernel is loaded to memory segment 0x1000.
• All screen and keyboard interaction is BIOS interrupt-driven.
• Command dispatch is done via a manual jump table.

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