Question on preprocessor directives
<p>If I use proprocessor directives to define which code an OS will run, like so:</p>

<pre><code>     #if winXP // Compiling for Windows XP
    platformName = "Microsoft Windows XP";
    #elif win2000 // Compiling for Windows 2000
    platformName = "Microsoft Windows 2000";
    #elif win7 // Compiling for Windows 7
    platformName = "Microsoft Windows 7";
    #else // Unknown platform specified
    platformName = "Unknown";
</code></pre>

<p>How does the system pick up which OS is being used?</p>

<p>This is an example from the book Visual C# 2010 Recipes, where the author says that the platformName variable (declaration ommitted), wil equal the OS above.</p>

<p>Thanks</p>
