What is a Kernel in Operating System

What is a Kernel in Operating System
What is a Kernel in Operating System

The kernel is the fundamental component of an operating system that manages computer and hardware processes. It primarily handles memory operations and CPU time. It is an essential component of an operating system. Using inter-process communication and system calls, the kernel functions as a bridge between applications and data processing conducted at the hardware level.

What is a Kernel in Operating System

A Kernel is computer software that serves as the operating system’s heart and soul. Because the Operating System controls the system, the Kernel also controls everything in the system. It is the most crucial component of an operating system. When a system boots, the Kernel is the first software that is loaded after the bootloader, since the Kernel is responsible for the rest of the system’s functionality for the Operating System, the Kernel is kept in memory until the Operating System is shut down.

When an operating system is loaded, the kernel is the first thing that loads into memory and remains there until the operating system is shut down. It is in charge of a variety of activities, including disc management, task management, and memory management.

It determines which processes should be allotted to the CPU for execution and which should be retained in the main memory for execution. It essentially serves as a bridge between user programs and hardware. The primary goal of the kernel is to handle communication between software, such as user-level applications, and hardware, such as the CPU and disc memory.

The Kernel is in charge of low-level activities including disc management, memory management, task management, and so on. It serves as a bridge between the user and the system’s physical components. When a process submits a request to the Kernel, this is referred to as a System Call.

A Kernel has a secured Kernel Space, which is a distinct section of memory that is inaccessible to other software applications. As a result, the Kernel code is loaded into this secure Kernel Space. Aside from that, the RAM utilized by other applications is referred to as the User Space. Because they are two distinct memory areas, communication between them is a little delayed.

Objectives of kernel

  • To connect a user-level application to a piece of hardware.
  • To determine the status of incoming processes.
  • Controlling disc management.
  • Controlling memory management.
  • To exert control over job management.

Kernel Functions in Operating System:

  • The kernel is the lowest level of abstraction in the operating system and acts as the direct interface between the hardware and the software layers. The Kernel performs the following basic functions:
  • Process administration: A process is something that is currently executing on an operating system. Because each operating process requires hardware, disc, memory, and interrupts, among other things, the kernel is in charge of allocating which resources to which processes. The information between these processes is communicated, and they are properly synchronized. The OS kernel ensures that the status is shared and recorded by device drivers and controllers, which are made up of three types of registers: instructions, status, and data.
  • Memory administration: Initially, all processes are stored to disc and have space given to them, creating a pool of processes. Memory management is the act of moving items from disc space to the main space, where they execute in the forefront. The kernel maintains track of the allotted space and transfers the processes back and forth in the same manner. Memory management is responsible for choosing to free or assign memory to any process. Addressing is done in three ways here: metaphorical, subjective, and practical.
  • Interrupt handling: It is handled by Kernel’s interrupt handler. An interrupt is a signal sent to the kernel in response to a system call request. A process may continue to operate until it receives an interrupt from another process and requests to be brought to the main memory. This task allocation is carried out by the kernel once it has reviewed the most appropriate interrupts that have occurred.
  • Communication through I/O: The communication of hardware devices, notably input and output devices, necessitates the kernel acting as a mediator between the hardware and software layers. As a result, these devices make requests to the kernel, which subsequently sends back interrupts and schedules them to be considered and performed as needed.
  • Device management: One of the most important duties of the operating system is to manage all of the devices that are linked with it. It is in charge of all hardware, software, storage, and input/output devices.

User Mode With Kernel Mode

Certain instructions must only be executed by the Kernel. As a result, the CPU only executes these instructions in Kernel Mode. Memory management, for example, should only be performed in Kernel-Mode. The CPU performs the processes specified by the user in the User Space when in User Mode.

Types of Kernel in Operating System

Kernels are classified into five categories. They are as follows:

Monolithic Kernels

Monolithic Kernels are ones in which user and kernel services are implemented in the same memory space, i.e. separate memory for user and kernel services are not utilized in this instance. This raises the size of the Kernel, which in turn increases the size of the Operating System. Because there is no distinct User Space and Kernel Space, the process will run quicker with Monolithic Kernels.

Types of Kernel in Operating System-Monolithic Kernels

Benefits of a Monolithic Kernel:

  • Excellent performance.
  • Only supports CPU scheduling, memory scheduling.
  • File management via System calls.

Monolithic Kernel Disadvantages:

  • The number of dependencies between system components and lines of code is in the millions.
  • The failure of a service causes the entire system to fail.
  • If a new service is added, the operating system must be changed.


A Microkernel differs from a Monolithic kernel in that the user and kernel services are implemented in separate locations, i.e. in the case of Microkernels, we utilize User Space and Kernel Space. Because we are using User Space and Kernel Space separately, the size of the Kernel is reduced, and therefore the size of the Operating System is reduced.

Because we utilize distinct areas for user services and kernel services, communication between application and services is done through message parsing, which slows down execution.

Microkernel-Kernel in Operating System

MicroKernel Advantages:

  • More dependable.
  • It is simple to add new services.

MicroKernel disadvantages:

  • There are a lot of system calls and context shifts.
  • Communication cuts down on total execution time.

Hybrid Kernel

A Hybrid Kernel is a cross between a Monolithic Kernel and a Microkernel. It makes use of the speed of the Monolithic Kernel as well as the flexibility of the Microkernel.

Hybrid kernels are micro kernels with some “non-essential” code in kernel-space to allow the code to execute faster than it would in user-space. As a result, some services, such as the network stack or filesystem, are performed in kernel space to decrease latency, although kernel code is still executed as servers in userspace.

Benefits of a Hybrid Kernel:

  • A hybrid of monolithic and microkernels.

Hybrid kernel disadvantages:

  • The same as a monolithic kernel.

Nano Kernel

As the name implies, the whole kernel code is very little in a Nanokernel, i.e. the code operating in the privileged mode of the hardware is very small. A kernel with a nanosecond clock resolution is referred to as a nanokernel.

Advantages of nano Kernel:

  • Offers hardware abstractions without system services.

Disadvantages of Nano Kernel:

  • It is used less due to being similar to microkernels.

Exo Kernel

Exokernel is an Operating System kernel created by the MIT Parallel and Distributed Operating Systems groups. The resource protection is separated from the management in this sort of kernel, which allows us to do the application-specific modification. The goal of the Exokernel is not to implement all of the abstractions. However, the goal is to impose as few abstractions as possible and to do so, the abstraction should be utilized only when necessary.

The goal of Exokernel is not to implement all of the concepts. However, the goal is to impose as few abstractions as possible, with the abstraction being utilized only when necessary. As a result, there will be no force separation in Exokernel, which distinguishes it from Monolithic Kernels and Microkernels. However, the intricate design is a disadvantage. The Exokernel’s design is quite sophisticated.

Advantages of Exo Kernel:

  • Least hardware abstractions.

Exo Kernel’s disadvantages:

  • There will be more work for application developers.
  • It has a complicated design.

The kernel is the most important and core component of an operating system. It is classified into five types: monolithic kernel, microkernel, hybrid kernel, nano kernel, and exokernel. A kernel’s functions include computer resource access, memory management, device management, and resource management.

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