Kernel of an Operating System

In simple words kernel is the central module of an operating system (OS). It is the part of the operating system that loads first, and it remains in main memory. Because it stays in memory, it is important for the kernel to be as small as possible while still providing all the essential services required by other parts of the operating system and applications. The kernel code is usually loaded into a protected area of memory to prevent it from being overwritten by programs or other parts of the operating system.

Typically, the kernel is responsible for memory management, process and task management, and disk management. The kernel connects the system hardware to the application software. Every operating system has a kernel. For example, the Linux kernel is used numerous operating systems including Linux, FreeBSD, Android and others.

A kernel includes an interrupt handler that handles all requests or completed I/O operations that compete for the kernel's services, a scheduler that determines which programs share the kernel's processing time in what order, and a supervisor that actually gives use of the computer to each process when it is scheduled. A kernel may also include a manager of the operating system's address spaces in memory or storage, sharing these among all components and other users of the kernel's services. A kernel's services are requested by other parts of the operating system or by application programs through a specified set of program interfaces sometimes known as system calls.

The kernel is not to be confused with the Basic Input/output System (BIOS).

Some kernels have been developed independently for use in any operating system that wants to use it. A well-known example is the Mach kernel, developed at Carnegie-Mellon University, and currently used in a version of the Linux operating system for Apple's PowerMac computers.

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