In Chapter 11, you learned how to create an external ActionScript file to define a custom class. You can also create external ActionScript files to simply share common code among multiple movies. Create the ActionScript code that appears many times in different movies, and keep that code in a text file outside the Flash movies. If you need to change the code, you only need to change it in one place.
External code can be incorporated into a Flash movie with the action #include. This action pulls in an external text file containing ActionScript and includes it in the existing script in the Script pane.