Windows 3.1

Windows 3.1 (codenamed Janus) is a series of 16-bit GUI operating environments for MS-DOS developed by Microsoft for use on personal computers. The series began with Windows 3.1, which was released on April 6, 1992 as a successor to Windows 3.0. Subsequent versions were released between 1992 and 1994 until the release of its successor, Windows 95. Support for all 16-bit versions of Windows ended on December 31, 2001.

On November 8, 1993, Windows 3.11 was released, which introduced problem corrections. On November 22, 1993, Windows 3.2, a version of Windows 3.11 in Simplified Chinese, was introduced.

Official support for Windows 3.1 ended on December 31, 2001. However, OEM licensing for Windows for Workgroups 3.11 on embedded systems continued to be available until November 1, 2008.

Windows for Workgroups
Windows for Workgroups is an extension to Windows 3.1x allowing communication with a workgroup using the SMB protocol over NetBIOS. The first version, Windows for Workgroups 3.1, was released in October 1992.

Windows for Workgroups 3.1
Windows for Workgroups 3.1 (codenamed Winball and Sparta during development) was released in October 1992, and is an extended version of Windows 3.1 that includes native networking support. It comes with SMB file sharing support via NetBIOS-based NBF and/or IPX network transport protocols, as well the introduction of the Hearts card game and VSHARE.386, a VxD version of SHARE.EXE.

Windows for Workgroups 3.11
Windows for Workgroups 3.11 (codenamed Snowball) was released on August 11, 1993. It supported 32-bit file access, full 32-bit network redirectors, and VCACHE.386 file cache, shared between them. WFW 3.11 requires a 386 machine to run, as standard mode support has been dropped.

A Winsock package was required to support TCP/IP networking in Windows 3.x. Usually third-party packages were used, but in August 1994, Microsoft released an add-on package (codenamed Wolverine) that provided TCP/IP support in Windows for Workgroups 3.11. Wolverine was a 32-bit stack, which gave it superior performance to most of the third-party TCP/IP Windows stacks available. However, it was only compatible with WFW 3.11, and lacked dial-up support. Wovlerine would later ship with Windows 95.

Windows 3.1

 * Microsoft Windows logo 1991.svgame: Janus
 * Release Date: April 6, 1992

New Features
 * TrueType font support.
 * 32-bit disk access
 * Minesweeper
 * Enhanced mode DOS/Windows interaction (some DOS programs can use Windows Clipboard)
 * Icons more detailed and can be dragged/dropped.
 * RAM limit increased to 64 MB (single applications limited to 16 MB)
 * Standard Multimedia support.
 * 32-bit disk access (Improved Windows performance)

Windows 3.1 Multimedia PC Version (Beta)

 * Codename: Bombay
 * Release Date: November 1992

New Features
 * Media Viewer
 * Video File Player.
 * Integrated sound and video with CD-ROM support.

Removed features
 * CGA graphics support (can be manually re-added from Windows 3.0xx)
 * Windows 2.xx application compatibility.
 * Reversi game

Windows 3.1xE (for Central and Eastern Europe)

 * Support for Cyrillic, Polish and other Central/Eastern European languages.

Windows 3.1J (Japan)

 * Release Date: 1993
 * Support for Japanese language

Modular Windows

 * Designed for the Tandy Video Information System.

Windows 3.11

 * Same Codename as Windows 3.1: Janus
 * Release Date: August 1993
 * Patch/bugfix release.

Windows 3.2

 * Release Date: November 22, 1993
 * Simplified Chinese character support.

Windows for Workgroups 3.1

 * Codename: Kato (Winball)/Jastro (Sparta)
 * Release Date: October 1992

New Features
 * Added native networking support via Windows real mode drivers. Comes with SMB file sharing via NetBIOS-based NBF and/or IPX network transport protocols>.
 * Hearts
 * VSHARE.386, the Virtual Device Driver Windows based version of the SHARE.EXE Terminate and Stay Resident program.

Windows for Workgroups 3.11

 * Codename: Snowball
 * Release Date: August 11, 1993 (shipped November 1993)
 * Requires 386 or better

New Features
 * Full 32-bit network redirectors, and the VCACHE.386 file cache, shared between them.

Windows NT 3.1
New Features
 * Codename: AXP/93
 * Release Date: July 27, 1993
 * NT version of Windows 3.1x.

Winsock
A Winsock package was required to support TCP/IP networking in Windows 3.x. Usually third-party packages were used, but in August 1994, Microsoft released an add-on package (codenamed Wolverine) that provided TCP/IP support in Windows for Workgroups 3.11. Wolverine was a 32-bit stack (accessible from 16-bit Windows applications via WinSock thunks), which gave it superior performance to most of the third-party TCP/IP Windows stacks available. However, it was only compatible with Windows for Workgroups 3.11, and lacked support for dial-up. The Wolverine stack was an early version of the TCP/IP stack that would later ship with Windows 95, and provided an early testbed for the 16-to-32-bit compatibility layer that was crucial to Windows 95's success.

Video for Windows
Release Date: November 1992 (Windows 3.1 and Windows 3.11)

Features
 * Audio Video Interleave (AVI) format for video.
 * Added a application programming interface that allowed software developers working on the Windows platform to add the ability to play or manipulate digital video to their own applications.
 * Included software for playing and manipulating digital video.

Windows for Pen Computing
Windows for Pen Computing 1.0 was a series of Microsoft-produced add-ons for Microsoft Windows versions in 1992 with additional tools for tablet PCs. Became obsolete due to Tablet PC support for Windows XP Tablet PC Edition in 2002.

Win32s
Windows 3.1'x was given limited compatibility with the then-new 32-bit Windows API used by Windows NT by another add-on package, Win32s. There was a rumor that Microsoft did not want to increment any mainstream Windows 3.1'x version to something like Windows 3.2 because it could be confused with the Win32 API or otherwise distract consumers from upgrading to a real 32-bit OS like the then-upcoming Windows 95 was, though Windows NT 3.1 and 3.5 were both 32-bit operating systems that looked similar in appearance. For testing of the new Win32s functions the game FreeCell was included.

DR-DOS compatibility
The installer to the beta release used code that checked whether it was running on Microsoft-licensed DOS or another DOS operating system (such as DR-DOS). The code ran several functional tests that succeeded on MS-DOS and IBM PC DOS, but resulted in a technical support message on competing operating systems. If the system was not MS-DOS, the installer would fail. Digital Research, who owned DR-DOS, released a patch within weeks to allow the installer to continue. Microsoft disabled, but did not remove, this warning message for the final release of Windows 3.1. When Caldera bought DR-DOS from Novell, they brought a lawsuit against Microsoft over the AARD code, which was later settled.