In as3 swf file, all actionscript byte(ABC) data is been defined by tag DoABC. By the way, there is another tag to define ABC data:DoABCDefine. DoABCDefine’s tag is 72.
Back to the question: Which tag will active DoABC to run？ After my test, I find the tag ShowFrame will trigger DoABC to run. After DoABC been executed, the all classes, variables, function are all been added to AVM(Actionscript Virtual Machine).