ActionScript 2.0
With Macromedia Flash MX 2004 and MX Professional 2004 came ActionScript 2.0. You have several new features that can be found in other programming languages, such as Java. You can finally program in a way it is meant to be. The new ActionScript 2.0 lets you create reusable, scalable, robust, and maintainable code. It also gives you more coding assistance and debugging information.
Object-Oriented Programming (OOP) model
The most important new feature of ActionScript 2.0 is the implementation of several object-oriented concepts and keywords such as class, interface and packages that are familiar to you if you used other an object-oriented programming language. You can create custom classes and extend the build-in classes.
Strict data typing
ActionScript 2.0 lets you specify data types for variables, function parameters and function return types. Strict data typing offers several benefits at compile time because it triggers compiler errors, helps you find bugs in your code and prevent you from assigning the wrong type of data to a declared variable. During authoring code hinting is activated in the ActionScript editor for the declared variables. By specifying data types to variables it can increase the performance at runtime.