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<H1><A NAME="SECTION00320000000000000000">Important parts of the kernel</A></H1>
<P>
The Linux kernel consists of several important parts: process
management, memory management, hardware device drivers, filesystem
drivers, network management, and various other bits and pieces.
Figure <A HREF="node7.html#figkerneloverview">2.1</A> shows some of them.
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<STRONG>Figure 2.1:</STRONG> Some of the more important parts of the Linux kernel.<BR>
<P>
<P>
Probably the most important parts of the kernel (nothing else
works without them) are memory management and
process management. Memory management takes care of assigning
memory areas and swap space areas to processes, parts of the
kernel, and for the buffer cache. Process management creates
processes, and implements multitasking by switching the
active process on the processor.
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<P>
At the lowest level, the kernel contains a hardware device
driver for each kind of
hardware it supports. Since the world is full of different
kinds of hardware, the number of hardware device drivers is
large. There are often many otherwise similar pieces of
hardware that differ in how they are controlled by software.
The similarities make it possible to have general classes
of drivers that support similar operations; each member of
the class has the same interface to the rest of the kernel
but differs in what it needs to do to implement them. For
example, all disk drivers look alike to the rest of the
kernel, i.e., they all have operations like `initialize the
drive', `read sector N', and `write sector N'.
<P>
Some software services provided by the kernel itself have similar
properties, and can therefore be abstracted into classes.
For example, the various network protocols have been
abstracted into one programming interface, the BSD socket library.
Another example is the <b>virtual filesystem</b> (VFS) layer
that abstracts the filesystem operations away from their
implementation. Each filesystem type provides an implementation
of each filesystem operation. When some entity tries to
use a filesystem, the request goes via the VFS, which routes
the request to the proper filesystem driver.
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<P><ADDRESS>
<I>Lars Wirzenius <BR>
Sat Nov 15 02:32:11 EET 1997</I>
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