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== Package Dependencies ==
A Linux distribution is essentially a Linux kernel and a range of packages. Each distribution conists consists of a vast array of packages, many of which are not installed by default when the operating system is first installed. The idea behind this is to keep in the size of the installed operating system to a minimum, encouraging users to only install a package when they actually need it. Consequently, there are many packages upon which GNUstep is dependent that are not installed by default on most Linux systems. Before we can embark on a GNUstep environment build, therefore, it is necessary to install these package dependencies. Fortunately, these can be installed using a single command:
<pre>
Each of these packages needs to be built and installed on your Linux system in order to gain access to the full power of Objective-C and to be able to work with the examples in the remainder of this book. Fortunately a single package called ''GNUstep Startup'' is provided that contains the source code for all four of the above packages. This package can be downloaded from the [http://wwwmain.gnustep.org/resources/downloads.php?site=ftp%3A%2F%2Fftp.gnustep.org%2Fpub%2Fgnustep%2F#core GNUstep.org website download page]. Be sure to download the latest ''stable'' release of the ''GNUstep Startup'' software.
Once the package has been download downloaded to a suitable work folder it can be unpacked as follows (where <version> is replaced by the version number of the package you downloaded):
<pre>
== Compiling Objective-C Code ==
Before an Objective-C program can be run it must first be compiled. Compilation is a process whereby the human readable Objective-C code in the source file (in our case hello.m) is converted to the machine code understood by the CPU. Prior to performing this compilation, however, the GNUstep environment must first be set up by executing the ''GNUstep.sh'', the location of which was provided at the end of the installation process. Execute this script exactly as outlined in the installation message, for example:
<pre>
