SET(MODIFIABLE)
     Determines whether a buffer can be modified by the user.
  Syntax
     SET (MODIFIABLE, buffer, {ON | OFF})
  Parameters
     buffer               The name of the buffer that you want to make
                          modifiable or unmodifiable.
     ON                   Makes a buffer capable of being modified.  This is
                          the default setting.
     OFF                  Prevents a user from making any changes to a
                          buffer except creating or deleting markers or
                          ranges, or deleting the entire buffer.