docx In an effort to create an open document standard, Microsoft in collaboration with ISO/IEC and Ecma, developed the Office Open XML standard in 2006. One of the filename extensions supported in this specification is the .docx extension, a text document filename extension. The .docx was introduced in Microsoft Office Word 2007 and has been supported ever since in later iterations. It has become the default filename extension for all text documents produced using Microsoft Office Word. Given the open source nature of the XML specification, more alternative document processing applications support read and write capabilities on documents saved with the .docx filename extension. This is in comparison to the .doc filename extension which is a proprietary asset owned by Microsoft.
rtf In its original conception, the .rtf format was a specification for formatting text and graphics principally designed to facilitate the interoperability of documents and text between Microsoft document processing applications. It eliminated the need for specialized translation software required to open documents in different versions of MS-DOS, Windows, and Macintosh. The specification is a proprietary filename format first developed by Microsoft in 1987 to be supported in Microsoft word 3.0 and all versions of Microsoft Office Word thereof. The latest revision, version 1.9.1, was released in 2008 and also marked the end of any further enhancements to the specification by Microsoft. Through unformatted text, control words, control symbols, and groups, a piece of text can be encoded into an .rtf format. All RTF readers then process .rtf formats by separating and acting on control information disparately from the actual text in the document. Though the RTF specification is proprietary asset of Microsoft, several non-Microsoft programs support both reading .rtf documents and creating .rtf. Microsoft Office Suite is still however the most dominant application associated with this specification.