/sys$common/syshlp/helplib.hlb EDIT, /TPU, /READ_ONLY  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  /READ_ONLY
  /NOREAD_ONLY (default)

  Determines whether exiting writes the main (or first) buffer to a
  file.  If you specify multiple input files on the EDIT/TPU command
  line, this qualifier applies to each buffer.  Does not affect other
  buffers you create during the editing session.

  /READ_ONLY is the same as /NOWRITE.  For EVE, this makes the MAIN (or
  first) buffer write-locked and also makes it unmodifiable, unless you
  used /MODIFY.  Use /READ_ONLY to view a file without making any
  changes.  For example, the following command lets you view a file
  named MEMO.TXT, so you can use cursor-movement commands but cannot
  change the text:

     $ EDIT/TPU memo.txt /READ_ONLY

  /NOREAD_ONLY is the same as /WRITE---on exiting, EVE writes out the
  MAIN (or first) buffer to a file if the buffer has been modified, and
  if necessary, EVE prompts you for the output file name.

  In EVE, the status line shows whether the buffer is read-only or
  write.  Also, you can change the read/write and modification
  attributes of the buffer during your editing session by using the SET
  BUFFER command.