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.
xlsx The .xlsx is an open source filename extension format developed by Microsoft in collaboration with ISO/IEC and ECMA. It is part of the Open Document family of file formats. The .xlsx is associated with spreadsheet authoring applications particularly with Microsoft's Office Excel 2007 and above. The format has existed since 2005 and is also supported by several other proprietary and open source spreadsheet authoring software other than Microsoft's Office Excel. The xlsx format is the default filename extension for all spreadsheet documents produced using Microsoft Office Excel 2007 SP2 and above.