Word processing involves using computers to prepare documents. Early mechanical word processors included the typewriter. The first use of the term "word processing" was by IBM in the late 1960s to describe their Magnetic Selectric typewriter and other electronic devices. Popular early PC word processors included WordPerfect 5.1 and early versions of Microsoft Word for DOS. Word 2007 and 2010 introduced new interfaces like the ribbon and backstage view and default file extensions changed from .doc to .docx. Alternatives to purchased software include free open-source options and cloud-based offerings from Google Docs and Microsoft SkyDrive.