If you have GUI-specific code in your scripts and declarations, you can have Silk Test Classic conditionally compile your code based on the values of the GUI specifiers - only code specific to a particular GUI is compiled (as well, of course, as all code that is not GUI-specific). This has the following two advantages:
You can also cause conditional compilation by using constants, which are evaluated at compile time.
Constants are not restricted to conditional compilation. You can use constants for any value that you want resolved at compile time.