The Flex and Flex Builder documentation includes information for users who have a variety of backgrounds. This section helps you understand how to approach the documentation, depending on your background and what you want to accomplish with Flex and Flex Builder. ...

Flex Builder is built on top of Eclipse, an open-source IDE, and it provides all the tools you need to develop Flex 2 and ActionScript 3.0 applications. It runs on Microsoft Windows, Apple Macintosh OS X, and Linux, and is available in several versions. Installation configuration options let you install Flex Builder as a set of plug-ins in an existing Eclipse workbench installation or to create an installation that includes the Eclipse workbench.

The Flex Builder installer provides the following two configuration options: Plug-in configuration This configuration is for users who already use the Eclipse workbench, who want to add the Flex Builder plug-ins to their toolkit of Eclipse plug-ins (for example, someone who also uses Eclipse to develop Java applications). Because Eclipse is an open, extensible platform, hundreds of plug-ins are available for many different development purposes.

Stand-alone configuration This configuration is a customized packaging of Eclipse and the Flex Builder plug- ins created specifically for developing Flex and ActionScript applications. The user interface of the stand-alone configuration is more tightly integrated than in the plug-in configuration, which eliminates much of the potential confusion that the open, multipurpose plug-in configuration might create. The stand-alone configuration is ideal for new users and users who intend to develop only Flex and ActionScript applications.
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Source: docs.brajeshwar.com