Flag between different platform

I found iPhone to Mouse Input C# script which might be useful for testing on window if I Can replace that iPhoneInput with Generic Input (Unity 3.0)... How can I know whether we are testing and building for iPhone or Windows? Does the unity has any #ifdef flags something like

ifdef iPhone

DOSomething();

endif

ifdef PC

DOSomething();

endif

You can use #if, #elseif and #else for platform dependent compilation

The defines you can use with it are described here:

http://unity3d.com/support/documentation/Manual/Platform%20Dependent%20Compilation.html