Syntax:  OPEN FILE file_spec

  Moves the cursor to the buffer containing the specified file.

  This command moves the cursor to its last editing position in the
  buffer containing the specified file.  If the file is not already in
  a buffer, LSE reads the file into a new buffer.  When LSE reads a
  file, it uses the list of source directories if you do not specify a
  directory in the file specification and if it cannot be found in the
  default directory.

  If the file is found in a read-only directory, LSE sets its
  modifiable state to off.  If the file is found in a read/write
  directory, its modifiable state is set to on.