Action Script 3.0 is a powerful, object-oriented programming language that signifies an important step in the evolution of the capabilities of the Flash Player runtime. The motivation driving Action Script 3.0 is to create a language ideally suited for rapidly building rich Internet applications, which have become an essential part of the web experience.
Earlier versions of Action Script offered the power and flexibility required for creating truly engaging online experiences. Action Script 3.0 now further advances the language, providing superb performance and ease of development to facilitate highly complex applications, large datasets, and object-oriented, reusable code bases. With Action Script 3.0, developers can achieve excellent productivity and performance with content and applications that target Flash Player.

Action Script 3.0 is based on ECMAScript, the international standardized programming language for scripting. Action Script 3.0 is compliant with the ECMAScript Language Specification, Third Edition (ECMA-262). It also contains functionality based on ongoing work on ECMAScript Edition 4, occurring within the ECMA standards body.

Action Script is executed by the Action Script Virtual Machine (AVM) built into the Flash Player. AVM1, the virtual machine used to execute legacy Action Script code, powers Flash Player today and makes possible a wide range of interactive media and rich Internet applications.

However, developers have started to push AVM1 to its limits; their project requirements now demand a major breakthrough. Action Script 3.0 introduces a new highly optimized Action Script Virtual Machine, AVM2, which dramatically exceeds the performance possible with AVM1. As a result, Action Script 3.0 code executes up to 10 times faster than legacy Action Script code.

Goals of ActionScript 3.0
We wanted Action Script 3.0 to deliver an improved, consistent programming model; compliance with industry standards; and performance an order of magnitude greater than what we delivered in the past. Although Action Script 3.0 represents a new programming model for the runtime, it is one that will be familiar to developers with a basic knowledge of object-oriented programming.

ActionScript 3.0 is designed to address the following goals:

• Safety: The language supports type safety so developers can write unambiguous, easily maintainable code.
• Simplicity:The language is intuitive enough for developers to be able to read and write programs without constantly consulting a reference manual.
• Performance: The language enables developers to write complex programs that perform efficiently and responsively.
• Compatibility: The language provides a short backward and forward compatibility path and a significant overlap with industry standards. Action Script 3.0 is a dialect of ECMAScript which formalizes the features of Action Script 2.0, adds the capabilities of ECMAScript for XML (E4X), and unifies the language into a coherent whole.