Syntax:  SET BUFFER MODIFIABLE boolean

  Changes the buffer modifiable state of the current buffer.

  The parameter value on sets the buffer state to modifi- able.  The
  parameter value off sets the the buffer state to unmodifiable.  See
  the documentation for the SET DIRECTORY READONLY command for
  information about how this state is set by default.

  RELATED COMMANDS:

     SET BUFFER                  SET DIRECTORY READONLY
     SET BUFFER CLOSE