WINDOWS NT

Windows NT

Windows NT 3.1, the first of the NT family
Company/ developer:	Microsoft
OS family:	{{{family}}}
Source model:	Closed source / Shared source
Stable release:	Windows Server 2003 R2 NT 5.2.3790  (December 6, 2005) [+/-]
Preview release:	Windows Vista NT 6.0.5472  (July 17, 2007) [+/-]
Kernel type:	Hybrid kernel
Default user interface:	Graphical User Interface
License:	Microsoft EULA
Working state:	Current
Website:

Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was originally designed to be a powerful high-level language-based processor-independent multiprocessing multiuser operating system with features comparable to Unix to complement workstation versions of Windows that were based on MS-DOS until 2001. It was the first 32-bit version of Windows. Windows XP and Windows Server 2003 are the latest versions of Windows NT.

Major Features

The main design goals of NT were portability, in that it could be built for a variety of 32-bit architectures, mainly Intel, but also new and upcoming RISC architectures. Another goal was compatibility with various competing API "personalities"-- while the main personality would always be the new 32-bit Windows Win32 API, NT would offer limited support for POSIX (subset of Unix) APIs and OS/2 APIs. Another goal was security-- for multiuser server solutions, NT would support per-object (file, function, role) Access Control allowing a rich set of security permissions to be applied to systems and services. NT also would have complete network support for Windows networks, inheriting the previous OS/2 LAN Manager network style, as well as Unix's TCP/IP networking (for which Microsoft would implement a TCP/IP stack derived from the BSD Unix stack).

Windows NT was the first version of Windows to utilize 32-bit "flat" virtual memory addressing on 32-bit processors. Its predecessor, Windows 3.1, used segmented addressing and switches from 16-bit to 32-bit addressing in pages. Early versions of Windows NT were supported on 32-bit Intel processors, and MIPS processors.

Windows NT 3.1 featured a core kernel providing a system API, running in supervisor mode, and a set of user-space environments with their own APIs (including the new Win32 environment, as well as an OS/2 1.1 text-mode environment and a POSIX environment).

Notably, in the first versions of Windows NT, several I/O driver subsystems, such as video and printing, were user-mode subsystems. In Version 4, the video subsystem would be integrated quietly into the kernel.

NT's kernel features full preemptive multitasking, where the kernel can interrupt running tasks to schedule other tasks, and the operating system doesn't rely on user programs to voluntarily give up control of the CPU, as in Windows 3.1.

NT features built-in networking, an integrated GUI, and a pervasive object security that allows for access control lists on almost any function or part of the system. This is also part of the new file system, NTFS, a journaled, secure file system created just for NT. NT also allows for other installable file systems, and with 3.1 and 3.51, allowed for the system to be installed on FAT or even OS/2's HPFS file system.

Market Share

NT has grown from being called "Nice Try" to passing Unix in 2005 for sales of servers, according to IDC, a market research firm based in Framingham, Massachusetts^{[citation needed]}. Others observe that Windows NT servers using IIS, ASP and ASP.NET by the 2000s had a diminishing share of web and corporate servers (under 30%) with UNIX dominating with over 70% of the market^{[citation needed]}. The entry-level $99 home edition of Windows XP (XP Home Edition) lacks the ability to run SQL Server databases and IIS Web servers and other corporate features found in Professional and Server versions, but NT is now a major platform for PC-based games. Since NT has become the base technology for workstations, it nearly completely dominates desktop and laptop workstations with Apple's Mac OS X a distant second and Linux third.^{[citation needed]}

Development

When development started in November 1988, Windows NT (using protected mode) was to be known as OS/2 3.0, the third version of the operating system developed jointly by Microsoft and IBM. In addition to working on three versions of OS/2, Microsoft continued parallel development of the DOS-based and less resource-demanding Windows environment (using real mode). When Windows 3.0 was released in May 1990, it was so successful that Microsoft decided to change the primary application programming interface for the still unreleased NT OS/2 (as it was then known) 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 development alone while Microsoft continued work on the newly renamed Windows NT. Though neither operating system would be as immediately popular as Microsoft's DOS or Windows products, Windows NT would eventually be far more successful than OS/2.

Microsoft hired a group of developers from Digital Equipment Corporation led by Dave Cutler to build Windows NT, and many elements of the design reflect earlier DEC experience with Cutler's VMS and RSX-11. The operating system was designed to run on multiple instruction set architectures and multiple hardware platforms within each architecture. The platform dependencies are largely hidden from the rest of the system by a kernel mode module called the HAL.

Windows NT's kernel mode code further distinguishes between the "kernel", whose primary purpose is to implement processor and architecture dependent functions, and the "executive". This has led some writers to refer to the kernel as a microkernel, but the Windows NT kernel no longer meets many of the criteria of a "microkernel", although this was the original goal of chief architect Cutler. Both the kernel and the executive are linked together into the single loaded module ntoskrnl.exe; from outside this module there is little distinction between the kernel and the executive. Routines from each are directly accessible, as for example from kernel-mode device drivers.

API sets in the Windows NT family are implemented as subsystems atop the publicly undocumented "native" API; it was this that allowed the late adoption of the Windows API (into the Win32 subsystem). Windows NT was the first operating system to use Unicode internally.

Releases

The first release was given version number 3.1 to match the contemporary 16-bit Windows; magazines of that era claimed the number was also used to make that version seem more reliable than a '.0' release. The NT version number is no longer used for marketing purposes, but is said to reflect the degree of changes to the core of the operating system[1]. The build number is an internal figure used by Microsoft's developers.

Supported platforms

Like Unix, NT was written in a high level language such as C. It can be recompiled to run on other processor systems, at the expense of larger and slower code. For this reason, NT was not favored initially for use with slower processors with less memory. It also proved far more difficult to port applications such as Microsoft Office which were sensitive to issues such as data structure alignment on RISC processors. Unlike Windows CE which routinely runs on a variety of processors, nearly all actual NT deployments have been on x86 architecture processors.

Windows NT 3.1 ran on Intel IA-32 (x86), DEC Alpha, and MIPS R3000 and R4000 processors. In order to prevent Intel x86-specific code from slipping into the operating system by developers used to developing on x86 chips, Windows NT 3.1 was initially developed using non-x86 development systems and then ported to the x86 architecture. This work was initially based on the i860 processor and later on the MIPS processors when Windows NT plans for the i860 were cancelled.

Windows NT 3.51 added support for PowerPC processors. Intergraph Corporation ported Windows NT to its Clipper architecture and later Windows NT 3.51 was ported to SPARC, but neither version was sold to the public as a retail product.

Windows NT 4.0 was the last major release to support Alpha, MIPS, or PowerPC, though development of Windows 2000 for Alpha continued until 1999, when Compaq stopped support for Windows NT on that architecture. Released versions of NT for Alpha were 32-bit only, although Alpha hardware was used internally at Microsoft during early development of 64-bit Windows 2000 for IA-64. Only two of the Windows NT 4.0 variants (IA-32 and Alpha) have a full set of service packs available. All of the other ports done by 3rd parties (Motorola, Intergraph, etc.) have few, if any, publicly available updates.

Windows XP 64-Bit, Windows Server 2003 Enterprise, and Windows Server 2003 Datacenter support Intel's IA-64 processors. As of April 25, 2005 Microsoft had released four editions for 'x64' (AMD64 or EM64T): Windows XP Professional x64 Edition, Windows Server 2003 Standard x64 Edition, Windows Server 2003 Enterprise x64 Edition, and Windows Server 2003 Datacenter x64 Edition.

The Xbox uses a heavily modified and stripped down Windows 2000 kernel. This kernel was heavily modified again for the Xbox 360 which runs on PowerPC. This version is not for separate sale, and is only available through acquiring an Xbox. Little is known about it.

Hardware requirements

The minimum hardware specification required to run each release of the professional workstation version of Windows NT has been fairly slow-moving until the 6.0 Vista release, which requires a minimum of 15 GB of free disk space plus an additional 5 GB of extra space for 6.0, a 10-fold increase in free disk space alone over the previous version.

'NT' designation

It is popularly believed that Dave Cutler intended the initialism 'WNT' as a pun on VMS, incrementing each letter by one, similar to the apocryphal story of Arthur C. Clarke's deriving HAL 9000's name by decrementing each letter of IBM. While this would have suited Cutler's sense of humor, the project's earlier name of NT OS/2 belies this theory. Another of the original OS/2 3.0 developers, Mark Lucovsky, states that the name was taken from the Intel i860 processor—code-named N10 (or 'N-Ten')—which served as the original target hardware. Various Microsoft publications, including a 1998 question-and-answer session with Bill Gates,^[1] reveal that the letters were expanded to 'New Technology' for marketing purposes but no longer carry any specific meaning.

The letters were dropped from the name of Windows 2000, though the box contained the phrase 'Built on NT technology'. This action ostensibly reflected Microsoft's intent to unify its home and business lines, then represented by Windows 98 and Windows NT 4.0, but this goal would not be achieved until the introduction of Windows XP. Some believe this to be the result of a trademark dispute between Microsoft and Nortel as on the bottom of the Windows NT 4.0 product boxes is a notice explaining that 'NT' is a trademark of Northern Telecom.

See also

• Architecture of the Windows NT operating system line
• Microsoft Windows
• NT Domain
• ReactOS (an open source project with the goal of providing binary- and device driver-level compatibility with Windows NT)
• Windows Server System
• Windows NT Startup Process

References

1. ^ Gates, Bill (June 5 1998). Q&A: Protecting children from information on the Internet. Retrieved on 2005-06-26.

External links

• Official Page
• 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