The Kernel is the heart of an Operating System.
The kernel's responsibilities include managing the system's resources (the communication between hardware and software components).
A kernel connects the application software to the hardware of a computer
Monolithic kernel
In a monolithic kernel, all OS services run along with the main kernel thread, thus also residing in the same memory area. This approach provides rich and powerful hardware access. The main disadvantages of monolithic kernels are the dependencies between system components — a bug in a device driver might crash the entire system — and the fact that large kernels can become very difficult to maintain.
Microkernel (MODULAR)
The microkernel approach consists of defining a simple abstraction over the hardware, with a set of primitives or system calls to implement minimal OS services such as memory management, multitasking, and inter-process communication. Microkernels are easier to maintain than monolithic kernels, but the large number of system calls and context switches might slow down the system because they typically generate more overhead than plain function calls.
