The Earliest Days of Microsoft Windows NT

The first operating systems as we might think of them today (or at least anything beyond a basic task manager) shipped in the form of Multics in 1969. Some of the people who worked on that then helped created Unix at Bell Labs in 1971. Throughout the 1970s and 1980s, Unix flowed to education, research, and corporate environments through minicomputers and many in those environments thought a flavor of BSD, or Berkeley Software Distribution, might become the operating system of choice on microcomputers. But the microcomputer movement had a while other plan if only in spite of the elder minicomputers.

Apple DOS was created in 1978 in a time when most companies who made computers had to mail their own DOS as well, if only so software developers could built disks capable of booting the machines. Microsoft created their Disk Operating System, or MS-DOS, in 1981. They proceeded to Windows 1 to sit on top of MS-DOS in 1985, which was built in Intel’s 8086 assembler and called operating system services via interrupts. That led to poor programmers locking down points in order to access memory addresses and written assuming a single-user operating system.

Then came Windows 2 in 1987, Windows 3 in 1992, and released one of the most anticipated operating systems of all time in 1995 with Windows 95. 95 turned into 98, and then Millineum in 2000. But in the meantime, Microsoft began work on another generation of operating systems based on a fusion of ideas between work they were doing with IBM, work architects had done at Digital Equipment Corporation (DEC), and rethinking all of it with modern foundations of APIs and layers of security sitting atop a kernel.

Microsoft worked on OS/2 with IBM from 1985 to 1989. This was to be the IBM-blessed successor of the personal computer. But IBM was losing control of the PC market with the rise of cloned IBM architectures. IBM was also big, corporate, and the small, fledgeling Microsoft was able to move quicker. Really small companies that find success often don’t mesh well with really big companies that have layers of bureaucracy. The people Microsoft originally worked with were nimble and moved quickly. The ones presiding over the massive sales and go to market efforts and the explosion in engineering team size was back to the old IBM.

OS/2 had APIs for most everything the computer could do. This meant that programmers weren’t just calling assembly any time they wanted and invading whatever memory addresses they wanted. They also wanted preemptive multitasking and threading. And a file system since by then computers had internal hard drives. The Microsoft and IBM relationship fell apart and Microsoft decided to go their own way.

Microsoft realized that DOS was old and building on top of DOS was going to some day be a big, big problem. Windows 3 was closer, as was 95, so they continued on with that plan. But they started something similar to what we’d call a fork of OS/2 today. So Gates went out to recruit the best in the industry. He hired Dave Cutler from Digital Equipment to take on the architecture of the new operating system.

Cutler had worked on the VMS operating system and helped lead efforts for next-generation operating system at DEC that they called MICA. And that moment began the march towards a new operating system called NT, which borrowed much of the best from VMS, Microsoft Windows, and OS/2 - and had little baggage. Microsoft was supposed to make version 3 of OS/2 but NT OS/2 3.0 would become just Windows NT when Microsoft stopped developing on OS/2. It took 12 years, because um, they had a loooooot of customers after the wild success of first Windows 3 and then Windows 95, but eventually Cutler and team’s NT would replace all other operating systems in the family with the release of Windows 2000.

Cutler wanted to escape the confines of what was by then the second largest computing company in the world. Cutler worked on VMS and RSX-12 before he got to Microsoft. There were constant turf battles and arguments about microkernels and system architecture and meetings weren’t always conducive with actually shipping code. So Cutler went somewhere he could. At least, so long as they kept IBM at bay. Cutler brought some of the team from Digital with him and they got to work on that next generation of operating systems in 1988.

They sat down to decide what they wanted to build, using the NS OS/2 operating system they had a starting point. Microsoft had sold Xenix and the team knew about most every operating system on the market at the time. They wanted a multi-user environment like a Unix. They wanted programming APIs, especially for networking, but different than what BSD had. In fact, many of the paths and structures of networking commands in Windows still harken back to emulating those structures.

The system would be slow on the 8086 processor, but ever since the days of Xerox PARC, everyone knew Moore’s Law was real and that the processors would double in speed every other year. Especially since Moore was still at Intel and could make his law remain true with the 286 and 386 chips in the pipeline. They also wanted the operating system to be portable since IBM selected the Intel CPU but there were plenty of other CPU architectures out there as well.

The original name for NT was to be OS/2 3.0. But the IBM and Microsoft relationship fell apart and the two companies took their operating systems in different directions. OS/2 became went the direction of Warp and IBM never recovered. NT went in a direction where some ideas came over from Windows 95 or 3.1 but mostly the team just added layers of APIs and focused on making NT a fully 32-bit version of Windows that could that could be ported to other platforms including ARM, PowerPC, and the DEC Alpha that Cutler had exposure to from his days at Digital.

The name became Windows NT and NT began with version 3, as it was in fact the third installment of OS/2. The team began with Cutler and a few others, grew to eight and by the time it finally shipped as NT 3.1 in 1993 there were a few hundred people working on the project. Where Windows 95 became the mass marketed operating system, NT took lessons learned from the Unix, IBM mainframe, and VMS worlds and packed them into an operating system that could run on a corporate desktop computer, as microcomputers were called by then.

The project cost $150 million, about the same as the first iPhone. It was a rough start. But that core team and those who followed did what Apple couldn’t in a time when a missing modern operating system nearly put Apple out of business. Cutler inspired, good managers drove teams forward, some bad managers left, other bad managers stayed, and in an almost agile development environment they managed to break through the conflicts and ship an operating system that didn’t actually seem like it was built by a committee. Bill Gates knew the market and was patient enough to let NT 3 mature.

They took the parts of OS/2 like LAN Manager. They took parts of Unix like ping. But those were at the application level. The microkernel was the most important part. And that was a small core team, like it always is.

The first version they shipped to the public was Windows NT 3.1. The sales people found it easiest to often say that NT was the business-oriented operating system. Over time, the Windows NT series was slowly enlarged to become the company’s general-purpose OS product line for all PCs, and thus Microsoft abandoned the Windows 9x family, which might or might not have a lot to do with the poor reviews Millennium Edition had.

Other aspects of the application layer the original team didn’t do much with included the GUI, which was much more similar to Windows 3.x. But based on great APIs they were able to move faster than most, especially in that era where Unix was in weird legal territory, changing hands from Bell to Novell, and BSD was also in dubious legal territory. The Linux kernel had been written in 1991 but wasn’t yet a desktop-class operating system. So the remaining choices most business considered were really Mac, which had serious operating system issues at the time and seemed to lack a vision since Steve Jobs left the company, or Windows.

Windows NT 3.5 was introduced in 1994, followed by 3.51 a year later. During those releases they shored up access control lists for files, functions, and services. Services being similar in nearly every way to a process in Unix. It sported a TCP/IP network stack but also NetBIOS for locating computers to establish a share and a file sharing stack in LAN Manager based on the Server Message Block, or SMB protocol that Barry Feigenbaum wrote at IBM in 1983 to turn a DOS computer into a file server. Over the years, Microsoft and 3COM add additional functionality and Microsoft added the full Samba with LDAP out of the University of Michigan as a backend and Kerberos (out of MIT) to provide single sign-on services.

3.51 also brought a lot of user-mode components from Windows 95. That included the Windows 95 common control library, which included the rich edit control, and a number of tools for developers. NT could run DOS software, now they were getting it to run Windows 95 software without sacrificing the security of the operating system where possible. It kinda’ looked like a slightly more boring version of 95. And some of the features were a little harder to use, like configuring a SCSI driver to get a tape drive to work. But they got the ability to run Office 95 and it was the last version that ran the old Program Manager graphical interface.

Cutler had been joined by Moshe Dunie, who led the management side of NT 3.1, through NT 4 and became the VP of the Windows Operating System Division so also had responsibility for Windows 98 and 2000. For perspective, that operating system group grew to include 3,000 badged Microsoft employees and about half that number of contractors. Mark Luovsky and Lou Perazzoli joined from Digital. Jim Alchin came in from Banyan Vines.

Windows NT 4.0 was released in 1996, with a GUI very similar to Windows 95. NT 4 became the workhorse of the field that emerged for large deployments of computers we now refer to as enterprise computing. It didn’t have all the animation-type bells and whistles of 95 but did perform about as well as any operating system could. It had the NT Explorer to browse files, a Start menu, for which many of us just clicked run and types cmd. It had a Windows Desktop Update and a task scheduler. They released a number of features that would take years for other vendors to catch up with. The DCOM, or Distributed Component Object Modeling and Object Linking & Embedding (or OLE) was a core aspect any developer had to learn. The Telephony API (or TAPI) allowed access to the modem. The Microsoft Transaction Server allowed developers to build network applications on their own sockets. The Crypto API allowed developers to encrypt information in their applications. The Microsoft Message Queuing service allowed queuing data transfer between services.

They also built in DirectX support and already had OpenGL support. The Task Manager in NT 4 was like an awesome graphical version of the top command on Unix. And it came with Internet Explorer 2 built in. NT 4 would be followed by a series of service packs for 4 years before the next generation of operating system was ready. That was Windows 5, or more colloquially called Windows 2000.

In those years NT became known as NT Workstation, the server became known as NT Server, they built out Terminal Server Edition in collaboration with Citrix. And across 6 service packs, NT became the standard in enterprise computing. IBM released OS/2 Warp version 4.52 in 2001, but never had even a fraction of the sales Microsoft did. By contrast, NT 5.1 became Windows XP and 6 became Vista in while OS/2 was cancelled in 2005.