The first line in a Hypertext Markup Language (HTML) file is the _____, which is a processing instruction indicating the markup language used in a document.
Probably the DOCTYPE would not be a component or perhaps an HTML tag. It allows the app or developer to know how and where to view the text, by suggesting the HTML (and perhaps another XML language) edition or specification would be used.
A document type specification, or DOCTYPE, seems to be a guideline associating a specific SGML as well as an XML document with either the concept of a document.
