In an operating system, the kernel is a computer program that is responsible for managing the operations of the computer and hardware. It is the core component of an operating system and is responsible for managing operations of memory and CPU time. The kernel acts as a bridge between applications and data processing performed at the hardware level using inter-process communication and system calls. It is responsible for various tasks such as disk management, task management, and memory management. The kernel has a process table that keeps track of all active processes and decides which process should be allocated to the processor to execute and which process should be kept in main memory to execute. The kernel is responsible for controlling all hardware resources via device drivers, arbitrating conflicts between processes concerning such resources, and optimizing the utilization of common resources such as CPU and cache usage, file systems, and network sockets).

The kernel is the most important part of the operating system and is the primary interface between the hardware and the processes of a computer. It is named a kernel because it operates inside the OS, just like a seed inside a hard shell. The kernel controls all of the main functions of the hardware, whether it’s a tablet, desktop, server, or any other kind of device. The kernel is one of the initial programs loaded up on memory before the boot loader.

There are mainly five types of kernels: monolithic kernels, microkernels, hybrid kernels, exokernels, and nanokernels. The most widely used kernel is the monolithic kernel, which is used in Unix, Linux, Open VMS, XTS-400, and other operating systems. In a monolithic kernel, the same memory space is used to implement user services and kernel services. Microkernels, on the other hand, provide only the essential services needed to implement an operating system, and all other services are implemented in user space. Hybrid kernels take advantage of the speed of monolithic kernels and the modularity of microkernels. Exokernels expose the hardware resources to the application level, and nanokernels are the smallest kernels that provide only the basic services needed to implement an operating system.