azw3 The American company Amazon is a recognized powerhouse when it comes to all things related to books. Their proprietary eBook readers dubbed the Kindle which was first released in 2007 is a testament to this. The .azw file format is the filename extension associated with eBooks designed to be read on Amazon's proprietary Kindle device and through their free but closed source Kindle software for smartphones, PCs, and Macs. The format is incompatible with any device other than kindle and its associated software. In order to open files saved in this format on non-kindle devices, one would have to convert the file to another format such as the open ePub format or PDF. Some converters can also convert other formats into .azw files which can later be opened on a kindle device or application.
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.