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Let's talk
about the kernel.

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To use computer hardware,
a kernel is needed.

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The kernel has core operating system
components and it dynamically loads drivers.

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And the kernel ensures
security, stability and performance.

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It's really the most essential part of
the operating system and it has main responsibilities.

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It is responsible for processes, it's
responsible for memory management, for file system

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management, for device management, for networking,
for interrupt handling and hardware communication.

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And it uses system calls
to provide user space interaction.

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What does that mean? Well, that means
that if you run an application in user

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space that needs to communicate with the
kernel, it uses a so called system call.

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That's a deep level instruction that you
will normally never find unless you are

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going to search for it or you
are going to use the audit subsystem.

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So let's talk about
user space and system space.

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The kernel audience
is system space.

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That is a privileged execution
environment where no restrictions apply.

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You can't have restrictions in system space
because it is about the kernel. And

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the kernel needs full access to the
hardware, which is used by using drivers.

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Drivers, also known as kernel
modules, are also a part

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of system space and applications
normally run in user space.

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And that is
a restricted environment.

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And for applications to access
components that are running in

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system space, as just
mentioned, system calls are used.

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Before continuing, I would like to make a drawing to make it
more clear what exactly this user space and system space is doing.