Microsoft Windows is a range of operating environments and operating systems for personal computers and servers. The range was first introduced by Microsoft in 1985 as an add-on to MS-DOS to counter Apple's new system, the Apple Macintosh, which used a graphical user interface (GUI). Microsoft Windows eventually came to dominate the world personal computer market with market analysts like IDC estimating that Windows has around 90% of the client operating system market. All recent versions of Windows are fully-fledged operating systems. Windows is proprietary closed source software: Microsoft Corporation owns the software's copyright and controls its distribution.
Windows was developed for IBM PC-compatible computers (these were based on Intel x86 architecture), and today, almost all versions of Windows are made for this hardware-platform (although Windows NT was written as a cross-platform system for Intel and MIPS processors, and later appeared on the PowerPC and DEC Alpha architectures). The popularity of Windows made Intel CPUs more popular and vice versa. In fact, the term Wintel became used to describe PC-compatible computers running a version of Windows.