What is "microkernel"

n. (context computing English) A minimal operating system kernel offering basic mechanisms rather than abstract services.

In computer science, a microkernel (also known as μ-kernel) is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system (OS). These mechanisms include low-level address space management, thread management, and inter-process communication (IPC).

If the hardware provides multiple rings or CPU modes, the microkernel may be the only software executing at the most privileged level, which is generally referred to as supervisor or kernel mode. Traditional operating system functions, such as device drivers, protocol stacks and file systems, are typically removed from the microkernel itself and are instead run in user space.

In terms of the source code size, as a general rule microkernels tend to be smaller than monolithic kernels, usually sizing at under 10,000 lines of code. The MINIX 3 microkernel, for example, has fewer than 6,000 lines of code.