Bulletin boards is a system called Usenet is an enormous, distributed, on-line bulletin board with about 100 million characters of messages in more than 4, 000 different topic groups flowing daily.

• 公告牌也叫Usenet系统，是一个巨大的、分布式的联机公告牌，每天流动的有一亿多字符的信息和4000多不同题目的传题组。