By default,the editor window displays an empty text buffer, called
  dbg_editor_main.  If you are debugging a program at the time you invoke
  the editor, however, the editor window displays this program, names the
  filled text buffer with its specification, and places dbg_editor_main
  on the buffer menu as an alternative text buffer.

  The editor allows you to create any number of text buffers by choosing
  New (for empty text buffers) or Open (for existing files) from the File
  menu.  The name of each buffer appears in the buffer menu.  You can
  cut, copy, and paste text across buffers by choosing items from the
  Edit menu and selecting buffers from the buffer menu.