BEGINNING_OF
     Returns a marker that points to the first position of a buffer or
     range.  If you use the marker returned by BEGINNING_OF as a parameter
     for the POSITION built-in, the current character position goes to this
     marker.
  Syntax
     marker := BEGINNING_OF ({buffer | range})
  Example
     beg_main := BEGINNING_OF (main_buffer);
     This assignment statement stores the marker at the beginning of the
     main buffer in the variable BEG_MAIN.
  Related Topics
     END_OF   POSITION   MARK