Linux is said to be a "free" operating system (OS). This
chapter explains exactly what that means and how it affects
the way Linux is distributed. It also provides an introduction to the
KDE desktop, its relation to Linux, and some of the more popular
office- related software used on Linux.
What Is Linux?
Linux is a computer operating system, the most important program your com-
puter runs. It controls all of the programs that run on your computer by allocat-
ing resources, interpreting your instructions (by using your mouse and
keyboard), sending output to the monitor, keeping track of all files, and per-
forming many other important tasks.
Linux is different from most operating systems in that it has been devel-
oped by scores of programmers around the world. Linux is free, both in the
sense that you don't have to pay for it (though you can, and many people do)
and in the sense that the source code (its internal pieces) is available to anyone
who wants to look at or modify it. Having its source code "open" makes it possi-
ble for anyone to try Linux out, find bugs, and submit fixes that go to a central
control point before making their way into future versions of Linux.
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Chapter 1
The kernel is Linux's central nervous system; it's the operating system code
that runs the whole computer. Though some advanced Linux users make modi-
fications to the kernel on their systems, you probably won't have anything to do
with it. However, you should know that this is the core of your computer's sys-
tem and that it is under constant development.
Because so many developers work on Linux, the pace of Linux development
is quick, and problems are usually found and addressed rapidly.
The Roots of Linux
Linux's lineage goes back to UNIX, the most proven operating system in the
world in that it (and its variants) has been the most used networked computer
OS for over three decades. UNIX was developed at Bell Telephone Laboratories
and designed to support many users working at many computers at one time, all
linked together and sharing information and resources. When using such an
operating system, more than one person can use a single computer's hardware
to do many things at once, and a single user can do more than one thing (multi-
task) on a single machine as well. This makes for more efficient use of resources
and a more powerful system.
Linux runs on a variety of platforms, including x86, PowerPC, DEC Alpha,
Sun Sparc, and ARM, so no matter what type of computer hardware you have,
Linux will probably run on it. Linux aims for POSIX (Portable Operating
System Interface for UNIX) compliancy. POSIX is a set of standards that defines
an interface between programs and operating systems. By sticking to these stan-
dards, software developers can be reasonably confident that their programs can
be ported easily to any POSIX- compliant operating systems, such as the various
versions of UNIX. This means that Linux users can take advantage of software
made for general UNIX systems.
Linux Performance
Linux has been praised for its stability--computers running the Linux OS have
been known to run months or even years at a time without crashing, freezing,
or having to be rebooted.
Linux machines are also known to be extremely fast because Linux is espe-
cially efficient at managing resources such as memory, computer power, and
disk space. In fact, much of the World Wide Web is powered by older comput-
ers running Linux and the Apache webserver. Additionally, organizations such
as NASA, Sandia, and Fermilabs have built powerful, yet inexpensive, supercom-
puters by combining groups of lesser-powered Linux machines and having them
all work together in clusters.
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Learning about the Pieces
Linux Distributions
Because Linux is freely available, any company (or individual) can take it, add
software to it, and offer the resulting compilation (either free or for sale) as a
Linux distribution. The result is a range of available distributions. Some of the
companies producing these distributions also make small modifications to the
Linux kernel and include their own software tools for managing and configuring
Linux in an effort to simplify installation and management. Although each distri-
bution varies in minor ways, most differ merely in the software they include.
The good news is that even if your distribution doesn't include a tool or
application you want, it usually can be downloaded free from the Internet.
Ways of Communicating with Linux: Text and Graphical
One way to communicate with Linux is by typing text at a command line, similar
to the C prompt (C:>) for anyone used to working with DOS. A text- based inter-
face requires the user to type specific commands with a specific syntax that the
operating system understands. The computer displays a prompt letting the user
know it is ready to receive a command. The place where the command is typed is
known as the command line. Anyone who used a personal computer in the mid-
1980s or earlier is probably familiar with some kind of text- based user interface.
Many utilities, or programs, are command-line based. This means that
instead of using a mouse button to access the program, you type a word into
what is called a terminal window when the computer displays a prompt. This
book will not discuss these utilities until the final chapter. Chapter 13 discusses
the command-line interface and some of these utilities, but you can rest assured
that this chapter is optional.
The other method of communicating with Linux is by way of a graphical
user interface (GUI).
This is often called the desktop and consists of the icons,
windows, dialog boxes, toolbars, and panels that you see when using Linux as a
point-and- click operating system. This is considered more user-friendly because
it provides visual clues you can use to get the computer to do something, instead
of requiring that you memorize myriad commands.
Using the KDE GUI is the focus of this book. Though we introduce the
command line and some of the commands associated with it, you should be able
to do everything that you need to do with the KDE GUI.
What Is KDE?
is a GUI, a piece of software that interacts with the operating system but is
not an integral part of it. It simply provides a means of communicating with it.
You might think of it as an interpreter between you and Linux.
GNOME is another popular desktop GUI that works with Linux. GNOME
and KDE are each created and maintained by different teams of software devel-
opers. Both function well, and making the choice between them is largely a mat-
ter of personal preference. We focus on KDE here because it's what we use in
our offices and because it is included in almost every Linux distribution.
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What Else Is Included?
Besides Linux itself and the KDE desktop, you'll find many other programs
included with your Linux operating system. KDE alone includes over 100 pro-
grams, such as image viewers, text editors, email programs, web browsers, and
games. You'll even find a free office software suite (OpenOffice) and a
Photoshop-like program (The GIMP), both of which are discussed in this book.
OpenOffice and The GIMP are generally considered to be the leading free
applications in their respective fields. For this reason we have given each one a
separate chapter.
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