How to compile package file?

I have an actionscript file,it has a package name,it locate C:\demo directory,like follows:

package demo{

import flash.display.*;

public class ABC extends Sprite{

  public function ABC(){

     ......

  }

}

}

Then I compile above code like following command,but it raise following error:

C:\>mxmlc demo\ABC.as

Loading configuration file C:\sdk\frameworks\flex-config.xml

C:\demo\ABC.as: Error: A file found in a source-path must have the same package structure '', as the definition's package, 'demo'.

Where is wrong above command?

Thanks