ActionScript 2.0
ActionScript 2.0 was released with Flash MX 2004, to account mostly for some shortcomings with class structures. A majority of the language still mirrors the syntax of ActionScript 1.0, but for the power users, there are a few notable differences.
The ActionScript 2.0 class structure now supports public, private, and static class members, as well as inheritance and interfaces. ActionScript 2.0 also allows for Strong Typing and Function Return typing.
For more detailed information and further description of all the new features of ActionScript 2.0, check out this ActionScript 2.0 primer at http://www.flash-mx.com/flash/actionscript_lott.cfm. Also, for more information on ActionScript, read ActionScript for Flash MX: The Definitive Guide and Essential ActionScript 2.0, both by Colin Moock and published by O’Reilly. Macromedia also posts the ActionScript Dictionary, which lists all available objects and their methods, including code examples, at http://www.macromedia.com/support/flash/action_scripts/actionscript_dictionary/.