Besides all the functions available with the normal "gcur"  command,
    the following key commands are added to mark and delete regions:
    
    
    ?   Help:  Print the available cursor key commands.
    
    a   Apply  to  All:   Apply  the  regions  and  points marked in the
        currently displayed data to all the remaining input.
    
    d   Delete:  Delete the region or point the graphics  cursor  is  in
        or near to.
    
    q   Quit:   Write  the marked regions and points to the output file.
        If there is more input data, display the next set.
    
    r   Mark Region:  The end point of the region is set  to  where  the
        graphics  cursor  is currently located.  When executed the first
        time, "r" marks the first boundary of the region and the  prompt
        "again:"  appears  in  the  status line.  When executed a second
        time, the second boundary of the region  is  set  to  where  the
        graphics  cursor  is  currently located, and a line representing
        the region is drawn on the graph.
        
        The graphics cursor can be at any  location  any  time  the  "r"
        command   is  invoked.   However,  if  another  key  command  is 
        executed between two "r" commands, the first one is aborted  and
        a new region is started.
    
    s   Mark  Single Point:  Mark the point where the graphics cursor is
        located.  An "x" will appear to indicate that the point has been
        marked.