A symbol or symbols that indicate the beginning or the end of a field, of a word, of an item of data, or of a set of data, such as a file, a record, or a block.

• 用来表明一个字段、一个字、一个数据项或诸如一个文档、一个记录或块的一组数据的开始或结束的一个或多个符号。