Microkernel Mac OS nanokernel KeyKOS Adaptive Domain Environment for Operating Systems LSE/OS EKA2 Poul-Henning Kamp Programmer's key Monolithic kernel XtratuM Old World ROM Hybrid kernel Rosetta (software) Single address space operating system Mac 68k emulator Zephyr (operating system) Exokernel OpenComRTOS Hardware-assisted virtualization Macintosh Toolbox Inter-process communication EROS (microkernel) Hardware abstraction Kernel (operating system) Mac OS 8 Mac OS X 10.0 Chorus Systèmes SA List of operating systems Symbian Copland (operating system) Verve (operating system) Classic Mac OS System 7 Mac OS 9