You can also add comments to a file in the ABL source code by adding comments to the Purpose section in the following format:
/*------------------------------------------------------------------------
    File        : GenericDataExporter
    Purpose     :
    Syntax      :
    Description :
    Author(s)   : abc
    Created     : Tue Nov 19 21:16:10 CET 2013
    Notes       :
  ----------------------------------------------------------------------*/
 
USING Progress.Lang.*.

BLOCK-LEVEL ON ERROR UNDO, THROW.

CLASS com.ClassA: 
END CLASS.