Some elements include a keyword in the element declaration that describes the data content of the element. Three keywords appear in the DTD: EMPTY, CDATA, and #PCDATA.
Specifies that the element has no data content that will be displayed in the online information. newline and xref elements are examples.
Represents "character data"; that is, the data content of the element is not recognized as markup.
Represents "parsed character data"; that is, the data content may include both text and markup characters that the Help System parser interprets accordingly.