What Is a Computer Kernel?

Dejan Cvetnarevic
Dejan Cvetnarevic

Updated · Aug 08, 2022

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You probably already know what an operating system a.k.a. OS is. However, if you come across the concept of a kernel, the difference between the two may not be that obvious.

So, what is a computer kernel

Let’s start with the basics.

Every computer has an OS, which makes it possible for you to run programs. It ensures that the different parts of your PC work together and programs can share information.

At the core of every OS is the kernel. More often than not, only programmers and those who like to tinker with their machines are actually familiar with it.

So, what exactly does the kernel do? Where does it operate? And are all kernels the same?

In this article, we’ll answer those and many other questions.

Let’s begin!

What Is a Computer Kernel?

A computer kernel is a subpart of an OS. Although it’s just a component, the kernel is responsible for handling a number of tasks while the OS has its own missions.

The kernel is typically loaded into the memory when a system boots up and remains resident until the system is shut down. It is the first piece of code that is executed when a user logs in, and it is responsible for initializing the system and starting the first user process.

If I had to define kernel, I’d call it the essential program at the center of an operating system. Since the OS manages the entire system, the kernel also has control over everything in it.

Think of a kernel as the conductor of an orchestra. A conductor doesn’t play anything himself but makes sure that all the instruments are playing in harmony.

Kernels reside in all sorts of OSs, from Linux to Windows and macOS.

Operating System vs. Kernel

OSs and kernels are two essential concepts in computing. While related, they’re not the same thing. Still, many PC users get the two terms confused.

So, let’s explain the difference between an operating system and a kernel and why it matters.

What separates these two concepts is that the OS is a package of data and software responsible for managing the resources of the system, while the kernel is an important program in it.

Operating systems are built on top of kernels. They provide a higher-level interface that is easier for users to interact with. They also include additional features and functionalities, such as a graphical user interface (GUI) and system tools.

Kernels are typically designed to be efficient and lightweight. They only include the essential functionality needed to run a computer. 

What Is the Function of the Kernel of an Operating System?

The kernel is a vital component of any operating system, and without it, a system would be unable to function. It links the computer’s hardware and software and is responsible for managing resources and controlling access to memory. 

The kernel also manages devices and processors.

So, what is the function of the kernel of an operating system? Let’s look at its key responsibilities:

  • Scheduling processes: Assigns a part of time (timeslice) to each process, starts new processes, and determines their states (running, waiting, or ended).
  • Resource allocation: Controls memory, peripheral devices, and CPU processes. Acts as a link between the resources and the processes. Allocates hardware to the components that need it.
  • Device management: Manages all devices connected to the system (I/O, storage devices, etc). Transfers information from them to the system.
  • Interrupt handling and system call: Switches control to processes with higher priority. Also deals with system calls.
  • Memory management: Allocates memory to different processes and programs and removes them once they’re finished. 
  • Process management: Creates, executes, and ends processes running in the system. Ensures that the system executes the relevant tasks.

User Space vs. Kernel Space

A computer’s virtual memory is divided into kernel space and user space. The OS implements kernel level threads and processes in the kernel space. Similarly, user space is where user threads are implemented.

User space and kernel space have different access rights. This user space vs kernel space difference means that user-space programs can only access user-space memory. Kernel-space programs, on the other hand, can access both user-space and kernel-space memory. 

The kernel space is secure, and that’s where its entire software is saved. This means you can’t interfere with it even if you have access to the user space. Any mistakes while coding in the kernel space could damage the entire system.

Kernel Types

In general, there are five main types of kernel:

Monolithic Kernel

The monolithic kernel is a type of kernel architecture. It implements all fundamental features of a computer, including managing files and memory. 

A monolithic kernel contains all of the operating system's essential components. The advantage of this design is that it simplifies development and debugging by keeping all of the code in one place. The disadvantage is that it can be challenging to add new features or modify existing ones without affecting the entire kernel.

Monolithic kernels typically appear in Unix-like operating systems. The Linux kernel, for example, is monolithic.

Microkernel

The most significant difference between this variation and monolithic kernels is the number of address spaces they support. Unlike the monolithic kernel, this type delegates user and kernel services to different address spaces.

Microkernels are small, modular kernels that manage only the most essential parts of the operating system. This design makes them much more lightweight and efficient than traditional monolithic kernels.

One of the microkernels’ benefits is that they can be easily customized for specific needs. They can also be more easily ported to new hardware platforms.

However, smaller components make microkernels more difficult to develop and maintain than monolithic kernels. This type can also introduce some security risks.

Hybrid Kernel

Next on our list is the hybrid kernel. This type is essentially an extension of microkernel architecture but with some monolithic attributes that enhance its performance.

A hybrid kernel allows for modularity. This means that features can be added or removed without affecting the entire kernel. It also provides more efficient communication between the different parts of the system.

Another advantage is that it can be more scalable than a monolithic kernel because its software can take advantage of multiple processors more effectively. Hybrid kernels are used in many modern operating systems, such as Windows NT and macOS.

Nanokernel

A nanokernel is a very small kernel that provides only the most basic services required by an operating system. This type is typically used in embedded systems where memory and resource constraints are severe.

By keeping the kernel small, more resources can be dedicated to other system parts, such as applications.

The nanokernel isn’t suitable for general-purpose operating systems. However, it can be used as the basis for more specialized embedded OSs.

Exokernel

Exokernel is an operating system kernel responsible for application-level management of hardware resources. This type of architecture isolates resource protection from management, allowing for app-specific customization.

An exokernel is a computer kernel that provides an application programming interface (API) for direct access to hardware resources. It’s a form of a microkernel, in that it defines minimal abstractions between the hardware and software layers of a system.

Unlike most microkernels, however, exokernels do not provide any abstractions for process management or inter-process communication (IPC). These are left to be implemented by user-level programs.

The exokernel is most commonly used in research and development rather than in production systems.

History of the Kernel

Before the introduction of the kernel, developers used to code actions directly to the processor. Without OSs, that was the only way to complete interactions between the hardware and software. That’s how most early computers in the 1950s and 1960s operated.

In 1969, programmer Per Brinch Hanses discovered that converting OSs to suit new hardware would be more difficult than creating a nucleus and building an OS. This was the first time the idea of kernel programming appeared.

This new nucleus stored all source code for facilitating communications and support systems.

In the early 1970s, a team at AT&T Bell Labs, led by Ken Thompson, developed Unix. Unix was a pioneering operating system that introduced many concepts that are now commonplace in operating systems. It consisted of a collection of programs that drive its operations and a kernel that runs them.

Apple launched its macOS in 1984 with the Macintosh personal computer. With the 8.6 version, it switched to a nanokernel design. The modern macOS uses a hybrid XNU kernel.

The Windows NT kernel is based on the microkernel developed by David Cutler, who also worked on the VMS operating system. The Windows NT kernel is a hybrid kernel, combining aspects of both the microkernel and the monolithic kernel types.

Wrap Up

Many people believe that kernel and OS are the same thing, but this isn’t true. The kernel is just a part of the OS, albeit the most important one.

Even if you never knew what it actually is, you’ve been using it since you got your first computer. Now you know exactly what it is that organizes all the processes and data in your PC.

FAQ.


What is the kernel of an OS?

A kernel is an operating system’s central part. It’s responsible for managing the operations of the computer and coordinating between the different parts of the OS. It also takes care of managing memory, processes, I/O (input/output) requests, and provides an interface for user programs to interact with the hardware.

Why is it called a computer kernel?

The term "kernel" comes from the Germanic word for "seed, grain." This kernel meaning makes a lot of sense — the kernel is the central core of an operating system, just like a seed at the heart of a fruit.

Is Linux a kernel or OS?

Linux is actually both a kernel and an operating system. The Linux kernel lies at the core of the Linux OS. It manages all of the system's resources and provides a platform for applications to run on. However, the term "Linux" usually refers to the operating system as a whole.

How do kernels work?

In the above article, we’ve covered what is a computer kernel and how it works by managing processes and resources. In short, they allocate each process a certain amount of time to run (timeslice) and then switch to the next one. Kernels manage processes by providing the necessary resources each of them needs to run properly.

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Dejan Cvetnarevic

Dejan Cvetnarevic

Dejan is a techie at heart who always dreamed of turning his fascination with gaming into a career. He finds working for TechJury a perfect opportunity to express his views of all kinds of different software. Being an avid reader, particularly of fantasy and sci-fi, Dejan pursued a degree in English Language and Literature. When not at his computer, he’s watching sports or playing tabletop games.

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