The Microsoft Windows NT reference article from the English Wikipedia on 24-Jul-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Microsoft Windows NT

Microsoft Windows NT is an operating system produced by Microsoft Corporation. It is the ancestor of their current flagship Windows XP.

When developments started, back in 1988, Windows NT was supposed to be a 32-bit, portable version of OS/2. At the time, OS/2 1.x was an operating system developed as a joint project between Microsoft and IBM. Although running in protected mode, it was only 16-bit and tightly coupled with the Intel 80286 processor architecture. IBM was very attached to the idea of providing its customers who bought PS/2 Intel 80286-based systems with a suitably advanced operating system.

In addition to working on 16-bit and 32-bit versions of OS/2, Microsoft continued working in parallel on DOS-based—and less resource-demanding—Windows. When Windows 3.0 was released in May 1990, it was so successful that Microsoft decided to change the GUI API for the still-unreleased 32-bit OS from an extended OS/2 API to an extended Windows API. This decision caused tension between Microsoft and IBM, and the collaboration ultimately fell apart. IBM continued OS/2 developments alone, while Microsoft renamed their portable 32-bit OS to "Windows NT". Windows NT would be far more successful than OS/2, due largely to Microsoft's market prowess.

The change between OS/2 API and the Windows API was possible because of the design of the NT kernel. The kernel implementation exposes a Native API that can't be used by applications (i.e. isn't documented). An application relies on subsystems (implemented using the Native API), which expose APIs for the user-mode applications. Windows NT has the following subsystems: OS/2, POSIX (both limited), DOS, Win16 and Win32. Win32 is the main Windows NT API for applications.

Microsoft hired a group of developers from Digital Equipment Corporation to build NT, and many elements reflect earlier DEC experience with VMS and RSX-11. NT uses a highly layered design, with the hardware hidden from the NT kernel by a hardware abstraction layer. The NT kernel also uses a client server model inspired by the Mach kernel, and was the first operating system to use Unicode internally.

It is interesting to note that compared to the 32-bit OS/2 2.0, Windows NT has an architecturally different kernel and different system calls. Let's also note that Microsoft has been necessarily involved in the creation of OS/2 2.0, as it has released a beta in the second half of 1990 already, along with a programmer SDK, and that OS/2 2.0 shares executable file formats with Windows 3.0. Therefore Microsoft must have been working on four and not just three different systems in the 1988-1990 period:

• DOS + Windows
• 16-bit OS/2
• 32-bit OS/2
• 32-bit successor of OS/2 with a different primary API

It is probable that when DEC people arrived at Microsoft, they disagreed with the state of OS/2 developments, and preferred to reimplement everything, taking as model their experience with VMS. The immaturity of OS/2 has been confirmed by the divergence of the 32-bit API from the 16-bit one, which prevented simple recompilation of applications.

The following are the major releases of Windows NT :

• Microsoft Windows NT 3.1 — released 1993 (22 floppy disks, or 3 + CD-ROM)
• Microsoft Windows NT 3.5 — released 1994 (Codename: Daytona)
• Microsoft Windows NT 3.51 — released 1995
• Microsoft Windows NT 4.0 — released 1996

It should also be noted that a version of Microsoft Windows NT for PowerPC processors was released:

• Windows NT 3.51 PowerPC
• Windows NT 4.0 PowerPC

The PowerPC versions required:

  601 or higher PowerPC-based system

  16MB of memory (although more is  recommended)

  CD-ROM drive (4X IDE or SCSI)

  540MB of available hard-disk space (110MB  for the operating system)

In addition to PowerPC (such as PrEP and CHRP-based machines manufactured by IBM and others) and x86 processors, Windows NT was available for the DEC Alpha AXP and MIPS R4000 architectures. Further, prototypical versions of Windows NT were generated for the SUN SPARC, although no publicly available version for that architecture was released. Indeed, a primary goal of the Windows NT design architecture was (and continues to be, in view of the recent ports of Windows Server to the AMD64 and Intel IA64 architectures) portability between processor architectures, despite the fact that support for the initial RISC architectures (Alpha AXP, MIPS and PowerPC) ended with Windows NT 4.0 (for Alpha AXP, support continued through August, 2000 with the release of Windows NT 4.0 Service Pack 6).

Moreover, the beta-version of Windows 2000, Windows 2000 RC3, was in fact published with support for the Alpha AXP architecture although the final version of Windows 2000 was not published for any architecture besides x86.

Microsoft Windows 2000 (which identifies itself as "NT 5.0" under the Control Panel) and Windows XP (which identifies itself as "NT 5.1") are continued progressions of the Windows NT source code:

• Microsoft Windows 2000 (Version 5.0)
• Microsoft Windows XP (Version 5.1)

The Windows NT line is now simply called Windows. For example:

• Microsoft Windows Server 2003 (Version 5.2)

The first release of Windows NT, version 3.1, was sold in "Advanced Server" and "Workstation" editions. (The version number was chosen to match the contemporary 16-bit Windows; magazines of that era claimed the number was also used to make the version seem more reliable than a ".0" release. Some urban legends say that the release was also named 3.1 to "one-up" the OS/2 v2.1 shipping at that time.) From version 3.5, "Advanced Server" was renamed "Server". From version 5.0 (Windows 2000) onwards, "Workstation" was renamed "Professional". A "Home Edition" was introduced with version 5.1 (XP), to mark the discontinuation of the previous MS-DOS based Windows system.

The origin and meaning of the NT name are disputed. It is popularly believed that lead developer Dave Cutler, intended the initialism "WNT" as a pun on VMS, incrementing each letter by one; while this would have suited Cutler's humor, the project's earlier name of "NT OS/2" belies this theory. Another early Windows NT engineer, Mark Lucovsky, states that the name was taken from the Intel i860 processor—code-named "N-Ten"—that served as the original target hardware. Various Microsoft publications expand NT to "New Technology", but officially the letters stand for nothing. Microsoft is rumored to have renamed Windows NT 5.0 to Windows 2000 after a confidential agreement with Northern Telecom (Nortel), who owns a trademark on the name "NT". It is also possible that NT stood for network, a feature in Windows NT.

See also

Microsoft Windows

History of Microsoft Windows

Windows: 1.0 | 2.0 | 3.x | NT | 95 | 98 | Me | 2000 | XP | Server 2003 | CE | PPC | WM | Longhorn | Blackcomb

External links

• Windows NT and VMS: The Rest of the Story, discussion of ancestry of NT by Mark Russinovich
• A Brief History of the Windows NT Operating System a Microsoft Presspass Fact Sheet
• The Architects: First, Get the Spec Right, an interview with David Cutler and Mark Lucovsky
• "Windows NT PowerPC Edition"

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