When you buy a copy of Windows 95 at a software store, you get a basic batch of operating system utilities and a preconfigured kernel. Linux is different. When you buy a Linux distribution--say Debian, Red Hat, or Slackware--you not only get all the basics you get with something like Windows 95, you also get almost everything you'd ever need in the way of applications. A typical distribution costs perhaps $50 and can be had for as little as $7.95 from bargain basement-type resellers (such as CheapBytes) (See www.cheapbytes.com). Some Linux books even contain a CD-ROM with a complete distribution on it. Imagine getting a complete operating system with 90% of all the software you'll ever need on the inside of a book cover?
Of course, you can always download Linux for free over the Internet. Many FTP sites carry all major Linux distributions and packages, and you can select from several package formats. But since a CD-ROM loaded with goodies can be had so inexpensively, why not spend a few dollars and get the whole shebang? It would take a long time to ftp an entire distribution; a CD-ROM makes a lot more sense.
There are several popular distributions that you can compare: Red Hat, Debian, Slackware, Caldera, Yggdrasil, MKLinux (for the Macintosh), and several others. They mostly all come with a gigabyte or more worth of applications and tools. The networking packages, for example, not only contain everything you need to connect to your ISP, but also to setup your own web server (the Apache and NCSA web servers are frequently bundled together). Not only do you have your choice of editors, but you get at least one LaTeX publishing package, several graphics packages, Postscript and SGML Viewers and parsing tools, and, of course, the emacs mega-editor. (It's more than a "word processor"; it's a way of life!) You also get numerous development tools including C/C++, python, perl, basic, Tcl/Tk, gawk, sed, java, smalltalk, lisp, and more. Several command shells come, including bash, tcsh, pdksh, and others. The list goes on and on.
Many of these packages can operate at the command line outside of a windowing environment or within X Windows itself. And you have your choice of windowing environments, too. Distributions usually come with the OpenLook window manager, fvwm, twm, and there are a host of other window managers that are only an ftp connection away. The Motif window manager is a commercial application and normally costs between $50 and $150. However, you can often find applications that have been compiled with static Motif libraries so you can take advantage of Motif widgets in those applications without shelling out extra dollars.
Newer experimental window managers are being developed all the time. Red Hat Linux version 4.0, for example, includes TheNextLevel desktop and fvwm2 window manager package. TheNextLevel contains a set of configuration files that use the m4 macro package so that your environment is built from source files each time you start X Windows. While it's more complicated than plain vanilla fvwm, once you get the hang of it, it's extremely powerful.
It can seem overwhelming to choose your distribution from all the possibilities. And time has changed how they compare, too. Red Hat and Debian are perhaps the most popular distributions currently. Slackware still commands a loyal following, and Caldera is probably the most commercial (and also the most expensive). My personal favorite is Red Hat, though I've heard great things about Debian.
Different distributions rely on different packaging mechanisms to track library dependencies and the database of installed packages. Red Hat, for example, is famous for its RPM (Red Hat Package Manager) software. Several other distributions have copied this, such as Caldera. Instead of uncompressing *.tar.gz files and installing them, you install *.rpm files which the package manager uncompresses and records into a database. The package manager acts as an installation and uninstallation utility among other things.
Since package managers can differ between distributions, even for kernels, it's best to pick a single distribution and stick with it. If you do upgrade from one distribution type to another, you should probably reformat your Linux partition(s) and restore only your user-specific data as appropriate. Don't mix distributions!
Often times this method of upgrading (reformating, reinstalling from scratch, and restoring user data) is the least troublesome in the long run anyway. Or you could just upgrade software and libraries and hope you don't screw up any dependencies along the way. If you use a good package manager like RPM, you should be able to back out of any upgrades that cause conflicts, hopefully. Be warned, however, that I've heard numerous horror stories in actual practice.
Which ever distribution you select, you will have a current Linux kernel with source code. The kernel is the core of your operating system that interfaces your hardware with your system software. It is the essence of an operating system. Linus Thorvalds, the person who created Linux, coordinates current development of the Linux kernel, and new releases arrive every few months, and sometimes even more frequently. No matter what distribution you decide on, you'll still be using the same kernel and basic software.
Copyright, David S. Jackson, 1997.