1.0 (1985), 3.1 (1992): DOS-based
Windows NT (1993): UNIX competitor
Windows 95 (1995): preemptive multitasking
Windows 98 (1998): networking support
Windows 2000 (2000): NT evolved
Windows XP (2001): true multiuser; Pro, Home versions
Windows Vista (2006): gazillions of versions
Windows 7 (2009): many versions
Windows 8 (2012): one-OS-for-all-platforms, touch-centric
Windows 10 (2015)