Most ActionScript classes are organized in the Top Level package. Classes that were new in Flash Player 8, such as BitmapData, Rectangle, and various filters classes, are in the flash.* packages.

 Top LevelThe Top Level package contains the core ActionScript classes and global functions.
 flash.displayThe flash.display package contains the BitmapData class for image manipulation.
 flash.externalThe flash.external package contains the ExternalInterface class.
 flash.filtersThe flash.filters package contains classes for the filter effects that were new in Flash Player 8.
 flash.geomThe flash.geom package contains geometry classes, such as Point, Rectangle, and Matrix, that support the BitmapData class and the bitmap caching feature, which were new in Flash Player 8.
 flash.netThe package contains classes for uploading and downloading files.
 flash.textThe flash.text package contains the TextRenderer class, which lets you set the quality used by advanced anti-aliasing and define custom settings for fonts used by advanced anti-aliasing.
 mx.langThe mx.lang package contains the Locale class, which supports multilanguage text.
 SystemThe System package contains the capabilities, the input method editor (IME), and security classes.
 TextFieldThe TextField package contains the StyleSheet class for applying CSS styles to text.