All objects in recent versions of ActionScript are defined by something
called classes. Think of classes as blueprints that determine the unique
combination of characteristics, actions, and reactions that comprises a
particular object of a certain type. By "object," we are talking about the
familiar things a Flash developer deals with every day: movie clips (the
MovieClip class), text fields (the TextField class), buttons, sounds, math
functions, components, you name it. They are all defined by classes.
As of Flash MX 2004 (aka Flash 7), classes are stored in external text files,
usually with the .as file extension, and imported into a SWF at compile time,
which is the point at which Flash gathers together all your ActionScript,
symbols, and other relevant content, and "compiles" them into the special
code structure (bytecode) of the SWF file played by the Flash Play... (more)