Fiwix

Fiwix is an operating system kernel based on the UNIX architecture and fully focused on being Linux compatible. It is designed and developed mainly for educational purposes, so the kernel code is kept as simple as possible for the benefit of students. It runs on the 32-bit x86 hardware platform, and is compatible with a good base of existing GNU applications.

The Linux kernel is currently too big for a student of computer science to be able to understand its internal structure and to study how it works, and tomorrow it will be even bigger than it is today. In contrast, the Fiwix kernel, due to its minimal structure, can be the entry-level kernel and can therefore be more suitable for education. For obvious reasons, this project is only focused on students of computer science and new OS enthusiasts who want to know more about the internal operation of a UNIX-like operating system.

Do not think of GNU/Fiwix as a new UNIX flavor with its own system utilities, libraries and compilers, etc. Think about GNU/Fiwix as a new Linux-like kernel that follows the GNU/Linux philosophy and takes the same advantage of the existing GNU applications.

Fiwix is probably the first kernel highly compatible (within its current limitations, of course) with the basics of the Linux kernel. That means any ELF-i386 binary compiled in a GNU/Linux system, can be executed natively in a GNU/Fiwix system without any type of emulation.

It is based on monolithic kernel design and it is written entirely in C language, leaving only for the Assembler the small needed parts.

http://www.fiwix.org/