Recently, I received some questions from beginners about the concept, and the connection in the ActionScript, Flash Builder, Flash CS5, MXML, AIR and RIA. Don’t contempt the simple questions like these, probably even some experience can’t reply the question from beginners like: Can I use AS1 or AS2 in Flash CS5 and Flash Builder 4?

Ok, don’t hurry. Let’s learn these concepts first.

ActionScript

ActionScript is a scripting language developed by Adobe. It is a dialect of ECMAScript, and is used primarily for the development of websites and software targetting the Adobe Flash Player platform, used on Web pages in the form of embedded SWF files. Originally developed by Macromedia, the trademark in the language is now owned by Adobe (which acquired Macromedia in 2005), though the language itself is "open source" in the sense that its specification is offered free of charge and both an open source compiler (as part of Adobe Flex) and open source virtual machine (Mozilla Tamarin) are available.

In addition, here is an introduce of ECMAScript.

Adobe Flash Builder

Adobe Flash Builder (previously known as Adobe Flex Builder) is an integrated development environment (IDE) built on the Eclipse platform meant for developing rich Internet applications (RIAs) and cross-platform desktop applications, particularly for the Adobe Flash platform. Support for cross-platform desktop applications was added in Flex Builder 3 with the introduction of AIR.

Adobe Flash CS5

Adobe Flash Professional CS5 software is the industry standard for interactive authoring and delivery of immersive experiences that present consistently across personal computers, mobile devices, and screens of virtually any size and resolution.

Simply, ActionScript is a scripting language similar JavaScript, Flash Builder and Flash CS5 are IDE tools, MXML is an XML-based user interface markup language, can be used in Flash Builder, RIA means rich Internet applications.

Back to the question before, Flash CS5 still uses AS3. In fact, ActionScript 3.0 is the core scripting language of the Flash Platform. AS1/2 be supported as well as AS3. But Flash Builder 4, Flex Builder 3, the Flex SDK (command line compile) FDT, Flash Develop, AIR, and similar, all require AS3(All Flex SDK based IDEs require AS3).