Sebastian Mihai's Snowdrop OS Is an Open Source, Educational 16-Bit Operating System for IBM PCs
Built with vintage hardware in mind, Snowdrop OS is an operating system made from the ground up — for no reason beyond curiosity.
Programmer Sebastian Mihai has released something a little unusual in the 21st century: an entirely functional home-brew operating system, complete with graphical user interface, running on 16-bit real-mode IBM-compatible hardware.
"Snowdrop OS was born of my childhood curiosity around what happens when a PC is turned on, the mysteries of bootable disks, and the hidden aspects of operating systems," Mihai explains of his creation. "It is a 16-bit real-mode operating system for the IBM PC architecture. I designed and developed this home-brew OS from scratch, using only x86 assembly language."
Despite being a hobby project, Snowdrop OS is surprisingly functional: In its current incarnation, the operating system includes a boot loader, a fully-functional kernel, a command-line interface, a text editor, a BASIC interpreter for in-OS coding, an assembler and debugger for x86 code, and even a Tetris clone dubbed aSMtris.
In addition to the command-line interface, the OS supports a graphical interface driven by a bundled framework — with an aesthetic evocative of classic machines like the original Apple Mac and Atari's ST family. "Snowdrop's GUI framework provides an abstraction for user applications which want to rely on buttons, checkboxes, etc, while using a mouse for input," Mihai explains. "Another advantage is that the GUI framework ensures a consistent look and feel for all applications which rely on it."
The operating system, which is currently in version 31, is provided as a floppy disk image bootable on vintage hardware and as a CD-ROM image, either of which can be installed on a hard disk if one is detected in the host system. Mihai has also released the full source code for the project, along with technical documents detailing its creation.
"I hope that Snowdrop can serve other programmers who are looking to get a basic understanding of operating system functions," Mihai writes. "Like my other projects, the source code is fully available, without any restrictions on its usage and modification."
Full details, downloads, and source code for Snowdrop OS are available on Mihai's website.