AO RTOS is small real time OS based on Active Object concurrency model
A cute and educational x86 OS
Real-Time Embedded Operating System
A UNIX-like kernel for the i386 architecture
Lorena es un sistema operativo escrito en C, C++ y Ensamblador.
Fenix/Free/Fast VDI
UEFI GTP fdisk is a disk partitionning tool running under UEFI/BIOS
Custom firmware and IDE for the VEX Cortex Microcontroller
a very fast full system simulator
Nanux Kernel
operating system for Intel 8086 / 8088
A simple os written in ASM
Real time microkernel