Platform Dependent Compilation

Unity includes a feature called Platform Dependent Compilation. It consists of some preprocessor directives that let you partition your scripts to compile and execute sections of code for one of the supported platforms. This functionality is also supported within Editor, so you can compile the code specifically for your mobile or console and test it in Editor.

This is useful if you're branching code for things, such as In-App Purchase or control mechanisms. To use the Platform Dependent Compilation feature, you use the pound or hash symbol, as shown in the following code:

void Start () {
  
  #if UNITY_EDITOR
    Debug.Log("Unity Editor");
  #endif
  
  #if UNITY_ANDROID
    Debug.Log("Android");
  #endif
  
  #if UNITY_IPHONE
    Debug.Log("iPhone");
  #endif
  
  #if UNITY_STANDALONE_OSX
    Debug.Log("Stand Alone OSX");
  #endif
  
  #if UNITY_STANDALONE_WIN
    Debug.Log("Stand Alone Windows");
  #endif
}

While this is brilliant for coding between platforms...