关于系统的消息类型:
写MESSAGE一定要加上TYPE
那么消息类型有几种呢
message types: "A", "E", "I", "S", "W", or "X"
One of the...possible message types "A", "E", "I", "S", "W", or "X" must be specified
For messages displayed...Messages with the type "S" are always displayed in the status bar, regardless of the dtype....The latter also applies to messages of the type "I" for PBO and LOAD-OF-PROGRAM....Messages of the type "X" always cause a runtime error.