Invokes a text editor. Unless you have selected a different
    editor by entering the SET EDITOR command, the TPU-based
    EVE editor is invoked. Use your editor to peruse the last read
    message. When you are done, enter the appropriate command to
    quit from your selected editor. If you decide to edit the message
    and want to keep a copy of the newly edited message, enter the
    appropriate command to exit (use the EXIT command in EVE) and
    supply a file name.