MikeOS

MikeOS is an operating system for x86 PCs, written in assembly language. It is a learning tool to show how simple 16-bit, real-mode OSes work, with well-commented code and extensive documentation. Features:

• A text-mode dialog and menu-driven interface
• Boots from a floppy disk, CD-ROM or USB key
• Over 60 system calls for use by third-party programs
• File manager, text editor, image viewer, games...
• Includes a BASIC interpreter with 46 instructions
• PC speaker sound and serial terminal connection

The code is completely open source (under a BSD-like license), and is written by Mike Saunders and other developers.