Microsoft Windows is the collective brand name of several software operating systems by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs).[25][26] The most recent client version of Windows is Windows Vista and the current server version is Windows Server 2008. The upcoming client and server versions of Windows, Windows 7 and Windows Server 2008 R2, are scheduled to be available at retail from October 22, 2009.Linux is a family of Unix-like computer operating systems. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone.[27] The name "Linux" comes from the Linux kernel, started in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU operating system, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux.[28]Predominantly known for its use in servers, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, Canonical Ltd. and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, supercomputers,[29] video game systems, such as the PlayStation 3, several arcade games, and embedded devices such as mobile phones, routers, and stage lighting systems.