Microsoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs).[2] Microsoft Windows came to dominate the world's personal computer market, overtaking Mac OS, which had been introduced in 1984. As of October 2009, Windows had approximately 91% of the market share of the client operating systems for usage on the Internet.

Apple is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad. Apple software includes the Mac OS X operating system; the iTunes media browser; the iLife suite of multimedia and creativity software; the iWork suite of productivity software; Aperture, a professional photography package; Final Cut Studio, a suite of professional audio and film-industry software products; Logic Studio, a suite of music production tools; the Safari internet browser; and iOS, a mobile operating system. As of August 2010, the company operates 301 retail stores[4] in ten countries,[5] and an online store where hardware and software products are sold.[6] As of May 2010, Apple is one of the largest companies in the world and the most valuable technology company in the world, having surpassed Microsoft.