The single-most easily identifiable application ever conceived and built for the desktop computer. Microsoft’s most popular product ever leveraged an interest in graphical user interfaces during the mid-1980 and the boom that was on at that time in the personal computer space.
Windows basically started off as a graphical operating system shell for the MS-DOS. But it soon became one of the biggest things in the personal computing space. Such was the dominance of Microsoft Windows that at one time more than 90% of the personal computers (including laptops) had a version of it installed on it.
Windows latest commercially available version is Windows 10. This version and some of its previous versions are also available for tablets, smartphones and other devices.
As of date, the biggest threat for Windows comes from Apples Mac OS. In terms of mobile platform, Windows has been squarely beaten by Android which is the dominant operating system for smartphones.