EXPORT, PROTECTED ..  Determine the scope of an Instance Var or Method
------------------------------------------------------------------------------


 SYNTAX:

   [ EXPORT:    | PUBLIC:  ]  
   [ PROTECTED: | PROTECT: | READONLY: ]
   [ HIDDEN:    | HIDE:    | LOCAL:    ]



 DESCRIPTION:

  This keywords define the default scope and visibility of all Data and
  Methods definitions to follow. 
  Defining Data and Methods as PROTECTED or HIDDEN gives us the tool to
  encapsulate our class, one of the key features of OOPs. Please note,
  that you can override the default scope by adding a PUBLIC, READONLY
  or LOCAL statement to the definition of each var and class var.


  EXPORT: or PUBLIC:
  
   This is the default setting. It declares all Methods, Vars and ClassVars
   as public, which means, that they can be invoked and accessed from inside
   the classes Methods as well as from an outside function, using a 
   reference to an object of this class :

    +--------------------------------------------------------------+
    |  /* PUBLIC vars */                                           |
    |   nA := ::nResult         // valid (inside a Method)         |
    |   nA := oDlg:nResult      // valid (anywhere)                |
    |   oDlg:nresult := 1       // valid (assign from anywhere)    |
    +--------------------------------------------------------------+



  PROTECTED: or READONLY:

   This allows reading and writing of instance variables from a method of
   the class, but rejects any writing to a var from the outside. Any attempt
   to do so will produce an Error with code 2.
   
    +--------------------------------------------------------------+
    |  /* PROTECTED Vars */                                        |
    |   nA := ::nResult         // valid (inside a Method)         |
    |   nA := oDlg:nResult      // valid (anywhere)                |
    |   oDlg:nresult := 1       // Prohibited !                    |
    +--------------------------------------------------------------+



  LOCAL: or HIDDEN:

   This is the most restricted form. LOCAL Data and Methods are not visible
   outside of the class, which limits their usage to the classes methods
   only.  Any attempt to assign / access a LOCAL Data, or invoke a LOCAL
   Method will result in an Error Code 1 or 3.

    +--------------------------------------------------------------+
    |  /* HIDDEN Vars */                                           |
    |   nA := ::nResult         // valid (inside a Method)         |
    |   nA := oDlg:nResult      // Prohibited !                    |
    |   oDlg:nresult := 1       // Prohibited !                    |
    +--------------------------------------------------------------+