A blank .swf file is not quite empty, inside of all your .swf files you will find the actionscript that defines the built in objects such as Math, String and Array but what does that code look like?

Well unfortuneatley when you publish to the .swf file format, all your actionscript is compiled into bytecode, so its no longer in its human readbable form. Unless you have a memory dump program, a hex editor and the .swf file format SDK, your not going to get at it in a hurry, but one guy Casper Schuirink has done all the hard work for us, and placed all the bytecode in human readable form A.K.A actionscript inside of a .fla file. You can view the code that the Flash MX Engineers wrote to intialize the predefined objects, methods and properties right here.