For questions specifically regarding the (DOS-based) 3.x series of the Microsoft Windows OS.
Microsoft Windows 3.0 was introduced in 1990. It was followed by 3.1 (released 1992) and 3.11 (1993), both also appearing as ‘Windows for Workgroups’ editions. In the Chinese market, version 3.2 was released as well.
It provided a GUI front-end to DOS, as well as support for features (such as memory-protected drivers) not available in DOS.