What is a kernel? Easily explained

Although they use it every day, many people are not sure what exactly a kernel is. If you came across this term and would like to find out more, this is the right place for you. In this practical tip, we explain what the kernel is all about.

What is a kernel? The facts simply explained

A kernel is permanently used in everyday computer work and is always in use for you. The intention is that you don't notice him. It is the interface between the software with a graphical user interface that you use and the system hardware.

• The kernel is a central module of an operating system. It is sometimes referred to as the "nucleus".
• It has different layers. The bottom layer forms the interface to the system hardware, such as network controllers or PCI Express controllers.
• The next layer is memory management, which allocates memory to each process. Your application software usually includes various such processes.
• The "Process Management" layer takes over time management and enables all processes on your computer to appear to be running in parallel. The kernel regulates all requests from programs, lines them up one after the other and can interrupt them if there are problems.
• The top layer is the file system. It assigns areas to processes on the HDD, i.e. the hard disk, and the main memory.
• The kernel regulates the entire path from system hardware to application software, which today is mostly operated by the user via a graphical user interface (GUI).
• Only the user area is no longer part of the kernel, but is referred to as "Shell", "Ring" or "Userland".
• A computer program sends system calls, so-called "system calls", to the kernel. This then makes the actual request in machine language to the CPU. The kernel knows the complete instruction set of the CPU, i.e. all machine instructions that it can execute.
• These system calls are triggered, for example, when you read or write files on the computer. This simple task also happens continuously in the background.
• In multi-user systems, the kernel also monitors access rights to files and hardware components.
• The Task Manager lists all processes that are managed by the kernel. If you end a process here, the Task Manager instructs the kernel to abort this process and to free up the allocated storage space.
• Since the kernel is used permanently, it is first loaded into the main memory after starting. This usually happens in a protected area that prevents it from being changed or deleted.
• Windows uses the NT kernel, on which several subsystems are based. Apple uses the XNU kernel. Linux systems such as Ubuntu and Android devices use the Linux kernel.
• The kernel is not the processor core, but the operating system kernel or system kernel.
• Multi-kernel operating systems can use the various cores of a multi-core processor like a network of independent CPUs.
• A kernel is also not an API or a framework like the NET framework.

Linux Mint: better kernel also better Windows 10?

In the next practical tip, we will show you how to find out which kernel you have under Linux. In many other practical tips we explain terms from the computer language, from software, such as VPN connection, BIOS and UEFI or firmware, to hardware terms, such as BUS, SSD and mainboard.