Chapter 1: What Is Linux?

Topics covered in this chapter:
1.1 What's An Operating system?
1.2 What's UNIX then?
1.3 How does Linux differ from UNIX?

Linux, By Definition:
Linux is a free version of the widely used UNIX operating system.


Red Hat Linux 7.0, with the KDE 2.01 Window Manager Running

The above definition probably is'nt helping you much if you don't know what Operating system is, and what UNIX is all about. So let's start at block one: What's an Operating system?

1.1 What's An Operating System?
Imagine you have a brand new computer. Imagine that nobody has put a CD or floppy into it,ever. That would mean that there is no software installed on the system. This would have major implications for that computer, because you would switch it on. It would beep a few times and then tell you that It couldn't boot an operating system. In other words, you can't do anything with a computer unless you have some very important software on it -- the Operating System.

An operating system is the layer between you, the user, and the hardware inside the computer. If you click the mouse over an icon on your screen, the operating system can cleverly interpret that you want to load the program that you are clicking on. For all of this to happen. The Operating system (or the OS or O/S) must know how to use a screen (to show you what's going on), to use a mouse (so you can move it around and click with it), to use your hard disk drive (to load up the data from it). It must also need to know pretty much everything else about the hardware installed inside your PC, ie: RAM, Floppy/CD drives, keyboards, joysticks, sound cards, scanners, etc.

So when you start typing a letter, for example, you have already loaded up a word processing piece of software. This software is called application software and is indipendant of the Operating System, but nonetheless, all of the time whilst the word processor application is running, it talks constantly to the O/S for vital information.

Okay, we've pretty much established that an O/S is vital, but what else does an O/S do:

An O/S in the simplest form will allow us to manage our files. So for instance, we could make 3 directories (sort of like folders in a filing cabinet) to store our files. We could call them Mary,Jim and Bob. We could arrange it so that we put all of Mary's files into the mary directory, and all of jim's into jim's and so on. That would make sense, instead of shoving them all into one misc directory. We should also be able to do the following with files:
...and probably a bit more.

Got the idea of what an Operating system is? Let's find out about a specific type of operating system called UNIX...

 1.2 What's Unix Then?

UNIX is one of the world's oldest and yet best operating systems around. There are many different types of UNIX, and Linux is just one of them. Most of UNIX's different flavours are still being updated and are still in use all over the world today. Here are some popular manufacturers and brands of UNIX, that you may or may not have heard of before:
With the exception of FreeBSD, there is a pretty grand fee to own one of the above versions of UNIX. Mainly large commercial organisations and universities have these. Most home users don't have the powerful hardware and the budget to own that sorta stuff.

UNIX is good because it is a multi-tasking O/S. This means that it can do more than one thing at a time. It's also a multi-user O/S. You can bet your bottom dollar bill that it's handy to have this, because it means that you can run more than one program on the same computer, and allow lots of users to do stuff at the same time.

Clever, huh?
Well, yeah. It is. But then there has to be a down side, yeah? Well. Unix is pretty boring, and traditionally, you needed to learn lots of commands and know how to program a bit of code, etc, etc before UNIX was much use to you.


In 1981, a small company based in Seattle called Microsoft released an operating system, which for some reason, was taken on by IBM to go on their new home/small office based computer: the IBM PC (or Personal Computer). This system was also not graphical. It required commands, in the same format as UNIX, but they were a little easier to use, albeit simpler and less powerful. The main pitfall of MS-DOS - (Microsoft's PC Operating System) was, that it had no multi-user, multi-tasking or networking support. By the early 1990's, this was really starting to wear on PC users. UNIX was still much, much better.


During the 80's, a firm called Apple had released another computer, which was seperate from the PC, and did not run any PC software, because it relied on it's own O/S, named MacOS. This time, Apple had decided to make an operating system that was graphical, and later, incorporated colour, pictures, icons and even sounds! Instead of typing all things into the keyboard as commands, the same actions could be made as clicks and movements with the mouse. A device that the PC had, but rarely used.
In a similar sense, and time, the UNIX world, still very different to the market of the PC and the Mac, had a graphical front-end to it's console, it was called X, or X Windows.

An early version of MacOS running away


In 1990, Microsoft eventually released Windows 3.0 (versions 1 and 2 were not even worth talking about. They were'nt even really graphical interfaces). UNIX was a 32 bit o/s, and here comes Windows, a 16 bit, single-tasking, single user, graphical interface for the PC. Still miles away from UNIX and X Windows, and even Apple's MacOS!

It took until 1995, with the advent of Microsoft Windows 95 for Windows to finally go 32 bit, multi tasking, and capable of being multi-user (although not best suited. Windows NT came along shortly after, to do that job).


1.3 How does Linux differ from UNIX?
During the time from 1991 to 1995, most students whom were accustomed to the power of UNIX and X, at university, would go home and look at their pitiful excuse of a 16 bit o/s and sit and wait for something better to roll along, one day, for the PC

Enter: Linus Torvalds

Linus was, in 1991, a student in Finland studying Computer programming at university. Obviously using a UNIX system (probably BSD) He went home, as millions did, to their PC, and wondered why it didn't do the same things as the big computers at uni did.
He got bored of MS-DOS after 10 minutes, and decided to start his own kernel, which is the code at the heart of every operating system, that addresses the hardware directly. He wanted it to be free to distribute. He finished the first Linux kernel in mid 1991. He had the 32 bit kernel, in which programs could be run under, but he didn't have any software to run on it.
Luckily, an ex-student in the USA, by the name of Richard Stallman had created a team of programmers devoted to free software, he called this the Free Software Foundation, who believed in making software free to distribute, and free to obtain the source code along with it. The GNU GPL (General Public License) that the Free Software Foundation (or FSF) made also stated that the authors of the software could charge for the software, as long as they are willing for it to be freely distributed. This is the way that the GNU (stand's for GNU's Not Unix) and all software under the GNU GPL would create (hopefully) a profit.
Stallman had been busy making a whole suite of software, for example: an editor called emacs, which is very popular today, and the bash (Bourne Again Shell), a command line interface based upon the original Bourne Shell, that comes with the BSD variant of UNIX. the FSF's software was entirely based upon the UNIX software suite, and essentially improved on it. The FSF were missing by 1991, only one really vital piece of software, to make it a fully fledged operating system: The Kernel

Linus and Stallman got together, put their code together, and Linux, or GNU/Linux (as it's properly named) was made.


In 2001, the year of writing, millions of people (approx. 15 million) are contributing to Linux every day, either by just using it or developing free software under the FSF's GNU GPL. Many popular titles are available for Linux today, such as:
...and millions more... check out www.freshmeat.net for examples.

Still not convinced about Linux? Why don't you read a short that I wrote on the benefit of Linux. It's mainly geared to Windows or Mac users that are or are not thinking of migrating to Linux. It goes over a few main subjects, such as:

An Introduction to Linux, The History of Linux, Does Free really mean Free?, The real benefits of Linux and Migrating to, or using both Windows and Linux
It's only around 6 or 7 pages, click HERE to read it.

The Linux Benefit is (C) Copyleft 2001 Alistair J. Ross
If you would like to hear about Linux from a different (but still positive) point of view, then why not check out this site, it's all about how anyone can own and use a Linux system for free, and how using Linux will actually benefit you more than other Microsoft based OS's: http://linux.umbc.edu/gits/about.html