There currently exist a multitude of incompatible document file formats.
Examples of XML-based open standards are DocBook, XHTML, and, more recently, the ISO/IEC standards OpenDocument (ISO 26300:2006) and Office Open XML (ISO 29500:2008).
Page description languages such as PostScript and PDF have become the de facto standard for documents that a typical user should only be able to create and read, not edit.
HTML is the most used and open international standard and it is also used as document file format.
The default binary file format used by Microsoft Word (.doc) has become widespread de facto standard for office documents, but it is a proprietary format and is not always fully supported by other word processors.