Windows NT — The 32-Bit Windows That Left DOS Behind

Windows NT is the 32-bit operating system Microsoft wrote from scratch, without relying on MS-DOS. The first release, Windows NT 3.1, and its server edition, Windows NT Advanced Server, were released to manufacturing on 27 July 1993. Microsoft's press release of that date said both products would be available within three weeks from resellers, systems integrators, computer makers, software retailers and Microsoft itself. So 27 July is the day the product was finished and handed over for production; it reached buyers in the weeks after.

NT is usually glossed as "New Technology". Putting the Windows name on it, and starting the numbering at 3.1 to match the Windows 3.1 of the day, signalled that it would look and work like the Windows people already knew. Underneath it was entirely different, and that NT line runs on through Windows 2000 and Windows XP to today's Windows 10 and 11.

Dates up to release

The 1988 and 1989 dates come from Microsoft's own article; the dates from 1991 on, and those for NT 3.5 and 4.0, are from Wikipedia. The final step is dated slightly differently in different places. The Register, citing G. Pascal Zachary's Showstopper!, puts the release to manufacturers on 26 July, and a Japanese history series in Mynavi News says the code left the team's hands on the 26th and was released on the 27th. This article uses the date of Microsoft's press release.

A designer from DEC's VMS

The project was led by Dave Cutler, who had led development of VMS, the operating system for DEC's VAX minicomputers, in the late 1970s. According to an article Microsoft published in 2016, Cutler left Digital Equipment Corporation in 1988 when his team's Prism project, with its new Mica operating system, was cancelled. A call from Bill Gates led to meetings with Gates, Ballmer and Myhrvold, and Cutler started at Microsoft on 31 October 1988. Colleagues from DEC's West Coast group, five with software expertise and six with hardware, soon followed.

The same article says the team numbered about 20 engineers in 1988 and about 150 when the first version shipped five years later. Wikipedia, citing Zachary's book, says 250 programmers wrote 5.6 million lines of code at a cost of US$150 million. Wikipedia also says many concepts in NT 3.1 were taken from VMS, Cutler's earlier system. DEC sued Microsoft, alleging that code from Mica had been used; under the out-of-court settlement, again according to Wikipedia, Microsoft agreed to make NT run on DEC's Alpha processor.

It began as OS/2

NT was not Windows from the start. Wikipedia says development began as "NT OS/2", a new version of the OS/2 system Microsoft was building with IBM. The success of Windows 3.0, released in May 1990, changed the plan: in August 1990 the team rebuilt the system around Win32, the Windows API extended to 32 bits. The Register, drawing on Zachary, describes the same August 1990 decision to give NT the Windows interface. IBM learned of the plan in January 1991, and the OS/2 partnership ended.

What was new

Windows 3.1 was an operating environment running on top of MS-DOS. NT replaced the operating system itself. Wikipedia sums up Cutler's goals in three parts.

NT 3.1 shipped for x86 and MIPS, with Alpha following. It supported multiple processors and gave each user an account with its own rights; logging on began with Ctrl+Alt+Del. It introduced the NTFS file system, built to survive hardware failures, and handled text internally in Unicode. Advanced Server could act as a domain controller for central management of users, and was intended to succeed Microsoft's LAN Manager.

In the release-to-manufacturing announcement, Paul Maritz, senior vice president of the systems division, said: "Windows NT is one of the largest software projects ever undertaken." The release said more than 70,000 developers and more than 10,000 corporate sites had tested the system before release, and that Microsoft had been running it internally for more than two years.

A heavy first release

The first version did not sell strongly. Wikipedia gives the minimum x86 requirements as a 25 MHz 386 with 12 MB of memory, and the recommended configuration as a 486 with 16 MB, well above the average PC of the time. COMPUTE! magazine's August 1993 cover story explained that NT was a new operating system rather than the next version of Windows 3.1, and noted the price it exacted in processor, memory and disk requirements. Thirty-two-bit applications were scarce.

Sales figures differ by source. Wikipedia says about 300,000 copies in the first year; The Register, citing Zachary, says fewer than 500,000 in the first year, half of the projected one million. According to Wikipedia, the workstation version cost US$495 and Advanced Server US$1,495.

The NT line is still running

The NT name disappeared from product names after NT 4.0 in 1996, but every Windows since has been built on NT. Microsoft's developer documentation assigns each Windows release an internal version number.

The turning point was Windows XP in 2001. The consumer line from Windows 95 to Windows Me ended still carrying MS-DOS-derived code, and with XP home users moved onto NT too. When Cutler received the US National Medal of Technology and Innovation in 2008, Bill Gates wrote in support of the nomination that with XP in 2001 NT became the basis for all of Microsoft's PC operating systems (as quoted in Microsoft's article).

Cutler stayed with NT for years. According to Microsoft's article, he stopped managing the whole project in 1996 but led kernel development until 2006, working with AMD to ship the first 64-bit x64 editions of Windows. He went on to work on the Azure cloud platform and the hypervisor for Xbox One.

For the wider Windows lineage see the Microsoft timeline and the operating systems timeline; for the company, see Microsoft.