Microsoft Word is the most widely used word processing software according to a user tracking system built into the software,[citation needed]. Microsoft estimates that roughly half a billion people use the Microsoft Office suite,[4] which includes Word. Many other word processing applications exist, including WordPerfect (which dominated the market from the mid-1980s to early-1990s on computers running Microsoft's MS-DOS operating system, and still (2014) is favored for legal applications) and open source applications OpenOffice.org Writer, LibreOffice Writer, AbiWord, KWord, and LyX. Web-based word processors, such as Office Web Apps or Google Docs, are a relatively new category.