Windows 2.1

Windows 2.1x (also known as Windows/286 or Windows/386) is a historical version of Windows graphical user interface-based operating systems. Windows/286 2.10 and Windows/386 2.10 were released on May 27, 1988, less than six months after the release of Windows 2.0. This is the first version of Windows which requires a hard disk.

Editions
Like Windows 2.0, two editions of Windows 2.1x were released with different CPU compatibility. However, the naming convention was changed to Windows/286 and Windows/386.

Like Windows 2.0, the 286 edition would run on 8086 hardware, only without HMA support. A few PC vendors shipped Windows/286 with 8086 hardware; an example was IBM's PS/2 Model 25, which included Windows/286, resulting in some customer confusion.

Windows 2.11
On March 13, 1989, Windows 2.11 was released in Windows/286 and Windows/386 editions, with some minor changes in memory management, AppleTalk support and faster printing and updated printer drivers.

Windows 2.11 was superseded by Windows 3.0 in May 1990, but supported by Microsoft for twelve years, until December 31, 2001.