ActionScript History

ActionScript 1.0 initially released in September 2000. This was bundled with Flash version 5 
and became the first version of ActionScript with influences from JavaScript and the ECMA-262 (Third Edition) standard, supporting the said standard's object model and many of its core data types.
Local variables may be declared with the var statement, and user-defined functions with parameter passing and return values can also be created.
Notably, ActionScript could now also be typed with a text editor rather than being assembled by choosing actions from drop-down lists and dialog box controls. With the next release of its authoring tool, Flash MX, and its corresponding player, Flash Player 6, the language remained essentially unchanged; there were only minor changes, such as the addition of the switch statement and the "strict equality" (===) operator, which brought it closer to being ECMA-262-compliant. Two important features of ActionScript that distinguish it from later versions are its loose type system and its reliance on prototype-based inheritance. Loose typing refers to the ability of a variable to hold any type of data. This allows for rapid script development and is particularly well-suited for small-scale scripting projects.

OOP Programming in ActionScript 1.0
Prototype-based inheritance is the ActionScript 1.0 mechanism for code reuse and object-oriented programming. Instead of a class keyword that defines common characteristics of a class, ActionScript 1.0 uses a special object that serves as a "prototype" for a class of objects. All common characteristics of a class are defined in the class's prototype object and every instance of that class contains a link to that prototype object.

ActionScript 2.0
ActionScript 2.0 was introduced in September 2003 with the release of Flash MX 2004 and its corresponding player, Flash Player 7. In response to user demand for a language better equipped for larger and more complex applications, ActionScript 2.0 featured compile-time type checking and class-based syntax, such as the keywords class and extends. (While this allowed for a more flexible object-oriented programming approach, the code would still be compiled to ActionScript 1.0 bytecode, allowing it to be used on the preceding Flash Player 6 as well. In other words, the class-based inheritance syntax was a layer on top of the existing prototype-based system.)
With ActionScript 2.0, developers could constrain variables to a specific type by adding a type annotation so that type mismatch errors could be found at compile-time. ActionScript 2.0 also introduced class-based inheritance syntax so that developers could create classes and interfaces, much as they would in class-based languages such as Java and C++. This version conformed partially to the ECMAScript Fourth Edition draft specification.

ActionScript 3.0
The latest ActionScript version. ActionScript 3.0 debuted with Adobe Flex 2.0 and its corresponding player, Flash Player 9. ActionScript 3.0 was a fundamental restructuring of the language, so much so that it uses an entirely different virtual machine. Flash Player 9 contains two virtual machines, AVM1 for code written in ActionScript 1.0 and 2.0, and AVM2 for content written in ActionScript 3.0. ActionScript 3.0 provides not only a significant enhancement in performance, but also a more robust programming model that lends itself to complex Rich Internet Application development.

The update to the language introduced several new features:
Compile-time and runtime type checking—type information exists at both compile-time and runtime.
Improved performance from a class-based inheritance system separate from the prototype-based inheritance system.
Support for packages, namespaces, and regular expressions.
Compiles to an entirely new type of bytecode, incompatible with ActionScript 1.0 and 2.0 bytecode.
Revised Flash Player API, organized into packages.
Unified event handling system based on the DOM event handling standard.
Integration of ECMAScript for XML (E4X) for purposes of XML processing.
Direct access to the Flash runtime display list for complete control of what gets displayed at runtime.
Completely conforming implementation of the ECMAScript Fourth Edition Draft specification.

this post just for testing with large text.. :-)
(From Wikipedia)