Mach Microkernel

Mach is a microkernel architecture originating at Carnegie Mellon University, aiming to simplify OS kernel design via message passing, tasks, and ports. It underpins NeXTSTEP and (in hybrid form) macOS, where it coexists with BSD components in the XNU kernel.

• Tasks (address spaces) and Threads (units of execution)
• Ports and Messages for inter-process communication
• Memory objects & virtual memory abstraction
• External pagers & user-space extension potential

Mach was integrated with 4.3BSD and I/O Kit to form the XNU (“X is Not Unix”) hybrid kernel: Mach handles low-level scheduling, IPC and VM; BSD layers manage filesystems, sockets, and process semantics; I/O Kit provides an object-oriented driver model (C++ based).

• NeXTSTEP
• macOS