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Microsoft is first shown early Macintosh prototypes and signs a contract with Apple to develop applications for it, but must not release any mouse-based applications for the PC before September 1983 (one year after the initially planned release date for the Macintosh).

Early 1982

Charles Simonyi starts Microsoft's application division after coming to Microsoft from XEROX PARC in 1981. The first application using a new kind of user interface he helps develop is Multiplan, an electronic spreadsheets application which is ported to many different computer systems. A word processing application is rumored to be under development as well.

Late 1982

DOS 2.0, to be released in 1983 with the new IBM PC/XT, will reportedly include a new "visual shell" that does not require the user to type in entire commands to perform simple tasks. This shell will be based on the Multiplan interface.

November 1982

Visi On, an advanced GUI for the IBM PC, is first demonstrated to the public at Fall COMDEX 82. It may have influenced Microsoft to develop a similar operating environment of its own.

Early 1983

DOS 2.0 is released, but does not include the new visual shell. Instead, the shell is eventually included with Microsoft's version of Unix called XENIX. Rumors begin circulating that Microsoft is working on a system similar to Visi On.

April 1983

At Sprint COMDEX 83, Microsoft announces their own mouse and a mouse-driven word processor called "Multi-Tool Word", using the same Multiplan interface. They plan to release more products as part of the Multi-Tool series in the future.

Sometime after May 1983

The new operating environment, to be released as part of Microsoft's Multi-Tool line of products, is shown to select members of the press. It may have been just a staged demo to sell the idea of Windows. UI design is changed significantly sometime after that.

Late summer 1983

Multi-Tool Word is renamed to Microsoft Word, as the original name was not well received in the public. The still unannounced operating environment may have been renamed to Microsoft Windows around this time as well.

November 10th 1983

The mysterious operating environment is announced under the name Microsoft Windows. A brief demonstration for the attendees shows the new tiling interface.

November 14th 1983

A special demonstration of Windows is held for InfoWorld staff at Microsoft's offices.

November 29th 1983

Windows is demonstrated at the Fall COMDEX 83 by Microsoft and several computer manufacturers, Wang and Zenith among them. The release date is originally set for April 1984.

Late February 1984

Microsoft holds a technical seminar for software developers and hardware manufacturers, though many feel like they learned nothing useful about developing applications for the new system. The release date is pushed back to May.

Early 1984

The UI recieves minor changes, most notably a new scrollbar design, and there is now only one help button on the right side of the status bar at the top of the screen.

March 23rd 1984

Windows is demonstrated at the West Coast Computer Faire. According to Microsoft's John Butler, the user interface has changed since last fall and will now support custom fonts. The new release date in May is confirmed.

Late March 1984

Olivetti introduces the M24 and M21 computers, also showing Windows running on them.

Late April 1984

Windows currently occupies around 70 kB of system memory, with desired memory use being around 50-60 kB, and recommended total memory size being 192 kB.

May 1984

It's clear that Windows still needs a lot more work before it's ready for release. The release date is changed again to fall 1984. Application developers receive their first software development kits, including a pre-release version of Windows. At the Spring Executive Conference in Phoenix, Microsoft's president John Shirley boldly predicts that "Windows will run on 80% of DOS computers by the end of the year". Windows is also shown at the MICRO-EXPO in Paris on May 24th.

June 12th-29th 1984

Atron Corporation holds several technical seminar, where they demonstrated their PC Probe and Software Probe programs running on pre-release versions of Windows. On June 26th, Tandy demonstrated Windows and other software running on their Model 2000 computer at the Boston Computer Society's general meeeting in Boston.

Mid 1984

Developers continue to recieve monthly releases of software development kits. The UI is further tweaked as some features are dropped or changed, such as the status bar at the top and the trash can. Microsoft also announces Windows will also run on top of its XENIX operating system.

August 1984

ACT Apricot announces new computers running MS-DOS. Windows is demonstrated on the Apricot Xi.

Fall 1984

An ad in several magazines shows Bill Gates next to a Tandy 2000 running Windows in color. The PC version is to remain monochrome for now. A version running on AT&T's PC6300 is also announced.

Early October 1984

The launch of Windows at Fall COMDEX 84 in November is cancelled and the release date delayed yet again to June 1985. By this time, Windows is considered vaporware by many.

31st October 1984

The final development release (DR5) is made and distributed to developers shortly after.

Late 1984 or early 1985

Windows memory usage has increased to around 156 kB, so the recommended total memory size was raised to 256 kB. Microsoft hopes they can still bring it back down to 192 kb before release.

January 1985

Tandy Trower joins the Windows development team as the fifth and final product manager, while Scott McGregor, Windows development architect and manager, leaves. His duties are taken over by Steve Ballmer so Windows can be finished in time.

31st January 1985

Alpha release is made and distributed to developers shortly after. It includes mostly stability improvements and support for running DOS applications under Windows.

Between January and May 1985

An updated Alpha release is made. It looks much like the January release, but includes new and improved applications, such as Cardfile and a Windows version of Macintosh Multiplan called Windows Plan.

8th May 1985

Beta release is made and distributed to developers shortly after. It was also ported to some non-PC-compatible computers, such as the RM Nimbus PC-186 and Zenith Z-100. It features significant improvements to the UI and bundled applications. The SDK is now distributed separately. The press believes a final release is close.

June 1985

Despite Microsoft's best efforts, Windows is still not quite ready. Steve Ballmer therefore decides to release a "Premiere Edition" to at least partially meet the summer 1985 deadline.

30th July 1985

The Premiere Edition is made and distributed to select members of the press. It looks much like the May Beta with some additional improvements. Around this time, a critical defect in memory management code is found, requiring a complete rewrite and restart of the testing procedure. Windows is delayed for the last time to fall 1985.

Fall 1985

In September, Tulip Computers ships a pre-release version of Windows with their PC compatibles, designating it "version 1.xx". More builds follow in October and early November with mostly under the hood improvements. Apple threatens to sue Microsoft due to Windows' similarity to the Macintosh interface, but Microsoft negotiates a license to use some of Macintosh design elements in Windows.

14th November 1985

The final build, branded as version 1.01, is made. Retail floppy disks will be ready the next day.

20th November 1985

Windows 1.01 is finally released in retail stores after more than 2 years of development. Initial reception is mixed. Microsoft holds a roast event for themselves to celebrate the completion of Windows.

January 1986

Version 1.02 is made. It only features additional localizations and minor updates to applications. It is only released in Europe.

August 1986

Version 1.03 is made. It added additional drivers and included various updates. It's a universal release, available in the US and elsewhere.

April 1987

Version 1.04 is made. Support for IBM's new PS/2 line of computers is added, as well as additional fixes. This is the last release before version 2.0 came out later that year. Windows is finally officially endorsed by IBM.

31st December 2001

Windows 1.0 is out of support after 16 years, becoming one of the longest support releases of Windows.