creating swf files?

I am trying to learn what I need to do to create a swf file from an
ActionScript 2.0 file using mtasc.  I have a taken a sample code from a book
and compiled it with mtasc and it works just fine as long as I use the swf
file that was also included with the sample.  If I instead compile
with "mtasc -swf x.swf -main -header 550:400:12 x.as" so that it makes the
swf file from scratch it doesn't work.

I ran flasm on both swf files and on the one that mtasc created.  Some code is
missing from the created file that is present in the original file and in the
file modified by mtasc when the swf file is reused.  The code that is missing
is as follows.

========================
  defineMovieClip 4 // total frames: 30

    frame 0
      stop
    end // of frame 0
  end // of defineMovieClip 4
 
  exportAssets
    4 as 'AvatarSymbol'
  end // of exportAssets

  frame 0
   
constants 'av', 'this', 'avatar', 'Avatar', 'rav', 'randomavatar', 'RandomAvatar'  
    push 'av', 200, 300, 0.0, 'this'
    getVariable
    push 'avatar', 5, 'Avatar'
    new
    varEquals
    push 'rav', 100, 100, 1, 'this'
    getVariable
    push 'randomavatar', 5, 'RandomAvatar'
    new
    varEquals
  end // of frame 0
============================

I am at a loss to understation what I need to do to create a working swf file
with mtasc.

I appreciate any help you can give me.

--
MTASC : no more coffee break while compiling