Windows NT is aproprietarygraphicaloperating system produced byMicrosoft as part of itsWindows product line, the first version of which,Windows NT 3.1, was released on July 27, 1993. Originally made for theworkstation, office, andserver markets, the Windows NT line was made available toconsumers with the release ofWindows XP in 2001. The underlying technology of Windows NT continues to exist to this day with incremental changes and improvements, with the latest version of Windows based on Windows NT beingWindows Server 2025 announced in 2024.[7]
The name "Windows NT" originally denoted the major technological advancements that it had introduced to the Windows product line, including eliminating the16-bit memory access limitations of earlier Windows releases such asWindows 3.1. Each Windows release built on this technology is considered to be based on, if not a revision of Windows NT, even though the Windows NT name itself has not been used in any other Windows releases sinceWindows NT 4.0 in 1996.
Windows NT provides many more features than other Windows releases, among them being support formultiprocessing,multi-user systems, a "pure"32-bit kernel with 32-bit memory addressing, support forinstruction sets other thanx86, and many other system services such asActive Directory and more. Newer versions of Windows NT support64-bit computing, with a 64-bit kernel and 64-bit memory addressing.
Product line
Windows NT is a group or family of products—like Windows is a group or family. Windows NT is a sub-grouping of Windows.
The first version of Windows NT,3.1, was produced forworkstation andserver computers. It was commercially focused—and intended to complement consumer versions of Windows that were based onMS-DOS (includingWindows 1.0 throughWindows 3.1x). In 1996,Windows NT 4.0 was released, including the new shell fromWindows 95.
Eventually, Microsoft incorporated the Windows NT technology into the Windows product line forpersonal computing and deprecated theWindows 9x family. Starting withWindows 2000,[8] "NT" was removed from the product name yet is still in several low-level places in the system—including for a while as part of the product version.[9]
Since Windows Vista, the Windows installation files, as well as the preinstallation environment used to install Windows, are stored in theWindows Imaging Format. It is possible to use theDeployment Image Servicing and Management (DISM) tool to install Windows from the command line and skip the GUI installer.[citation needed]
Naming
It has been suggested thatDave Cutler intended the initialism "WNT" as a play onVMS,incrementing each letter by one.[10] However, the project was originally intended as a follow-on toOS/2 and was referred to as "NT OS/2" before receiving the Windows brand.[11] Two of the original NT developers,Mark Lucovsky andDave W. Plummer,[12] state that the name was taken from the original target processor—theIntel i860, code-named N10 ("N-Ten").[13] A 1991 video featuringBill Gates and Microsoft products specifically says that "Windows NT stands for 'New Technology'".[14] Seven years later in 1998, during a question-and-answer (Q&A) session, he then revealed that the letters were previouslyexpanded to such but no longer carry any specific meaning.[15] The letters were dropped from the names of releases from Windows 2000 and later, though Microsoft described that product as being "Built on NT Technology".[8][16]
"NT" was a trademark of Northern Telecom (laterNortel), which Microsoft was forced to acknowledge on the product packaging.[citation needed]
Major features
One of the main purposes of NT is hardware and software portability. Various versions of NT family operating systems have been released for a variety of processor architectures, initiallyIA-32,MIPS, andDEC Alpha, withPowerPC,Itanium,x86-64 andARM supported in later releases. An initial idea was to have a common code base with a customHardware Abstraction Layer (HAL) for each platform. However, support for MIPS, Alpha, and PowerPC was later dropped inWindows 2000. Broad software compatibility was initially achieved with support for severalAPI "personalities", includingWindows API,POSIX,[17] andOS/2 APIs[18]—the latter two were phased out starting with Windows XP.[19] PartialMS-DOS and Windows 16-bit compatibility is achieved on IA-32 via an integratedDOS Virtual Machine—although this feature is not available on other architectures.[20]
NT has supported per-object (file, function, and role)access control lists allowing a rich set of security permissions to be applied to systems and services. NThas also supported Windows network protocols, inheriting the previous OS/2LAN Manager networking, as well asTCP/IP networking (for which Microsoft used to implement a TCP/IP stack derived at first from aSTREAMS-based stack fromSpider Systems, then later rewritten in-house).[21]
Windows NT 3.1 was the first version of Windows to use 32-bit flat virtual memory addressing on 32-bit processors. Its companion product, Windows 3.1, used segmented addressing and switches from 16-bit to 32-bit addressing in pages.
Windows NT 3.1 featured a core kernel providing a system API, running insupervisor mode (ring 0 in x86; referred to in Windows NT as "kernel mode" on all platforms), and a set of user-space environments with their own APIs which included the new Win32 environment, an OS/2 1.3 text-mode environment and a POSIX environment. The fullpreemptive multitasking kernel could interrupt running tasks toschedule other tasks, without relying on user programs to voluntarily give up control of the CPU, as in Windows 3.1 Windows applications (although MS-DOS applications were preemptively multitasked in Windows starting withWindows/386).
Notably, in Windows NT 3.x, several I/O driver subsystems, such as video and printing, wereuser-mode subsystems. In Windows NT 4.0, the video, server, and printer spooler subsystems were moved into kernel mode. Windows NT's firstGUI was strongly influenced by (and programmatically compatible with) that from Windows 3.1; Windows NT 4.0's interface was redesigned to match that of the brand-newWindows 95, moving from theProgram Manager to theWindows shell design.
NTFS, a journaled, secure file system, is a major feature of NT. Windows NT also allows for other installable file systems; NT can also be installed onFAT file systems, and versions 3.1, 3.5, and 3.51 could be installed onHPFS file systems.[22]
Microsoft decided to create a portable operating system, compatible withOS/2 andPOSIX and supportingmultiprocessing, in October 1988.[24] When development started in November 1989, Windows NT was to be known asOS/2 3.0,[25] the third version of the operating system developed jointly by Microsoft andIBM. To ensure portability, initial development was targeted at theIntel i860XRRISC processor, switching to theMIPSR3000 in late 1989, and then theIntel i386 in 1990.[13] Microsoft also continued parallel development of the DOS-based and lessresource-demanding Windows environment, resulting in the release ofWindows 3.0 in May 1990.
Windows 3.0 was eventually so successful that Microsoft decided to change the primaryapplication programming interface for the still unreleased NT OS/2 (as it was then known) from an extended OS/2 API to an extendedWindows 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 immediately be as popular as Microsoft's MS-DOS or Windows products, Windows NT would eventually be far more successful than OS/2.
Microsoft hired a group of developers fromDigital Equipment Corporation led byDave Cutler to build Windows NT, and many elements of the design reflect earlier DEC experience with Cutler'sVMS,[26]VAXELN andRSX-11, but also an unreleased object-based operating system developed by Cutler at Digital codenamedMICA.[27] The team was joined by selected members of the disbanded OS/2 team, includingMoshe Dunie.[10]
Windows 2000 architecture
Although NT was not an exact clone of Cutler's previous operating systems, DEC engineers almost immediately noticed the internal similarities. Parts ofVAX/VMS Internals and Data Structures, published byDigital Press, accurately describe Windows NT internals using VMS terms. Furthermore, parts of the NT codebase's directory structure and filenames matched that of the MICA codebase.[10] Instead of a lawsuit, Microsoft agreed to pay DEC $65–100 million, help market VMS, train Digital personnel on Windows NT, and continue Windows NT support for the DEC Alpha.[26]
Like VMS,[26] Windows NT's kernel mode code distinguishes between the "kernel", whose primary purpose is to implement processor- and architecture-dependent functions, and the "executive". This was designed as a modifiedmicrokernel, as the Windows NT kernel was influenced by theMach microkernel developed byRichard Rashid at Carnegie Mellon University,[28] but does not meet all of the criteria of a pure microkernel. Both the kernel and the executive arelinked together into the single loaded modulentoskrnl.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; this allowed the late adoption of the Windows API (into the Win32 subsystem). Windows NT was one of the earliest operating systems to useUCS-2 andUTF-16 internally.[citation needed]
Windows NT uses a layered designarchitecture that consists of two main components,user mode andkernel mode. Programs and subsystems in user mode are limited in terms of what system resources they have access to, while the kernel mode has unrestricted access to the system memory and external devices. Kernel mode in Windows NT has full access to the hardware and system resources of the computer. The Windows NTkernel is ahybrid kernel; the architecture comprises asimple kernel,hardware abstraction layer (HAL), drivers, and a range of services (collectively namedExecutive), which all exist in kernel mode.[29]
Windows NT is written inC andC++, with a very small amount written inassembly language.[31] C is mostly used for the kernel code while C++ is mostly used for user-mode code. Assembly language is avoided where possible because it would impedeportability.[32]
Home Single Language, Home China, Home, Pro, Pro Education, Pro for Workstations,[46] Enterprise, Education, S, IoT Core,Mobile, Mobile Enterprise[47][48]
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. Also the Novell IPX protocol was apparently licensed only to 3.1 versions of Windows software.[citation needed]
The NT version number is not now generally used for marketing purposes, but is still used internally, and said to reflect the degree of changes to the core of the operating system.[51] However, for application compatibility reasons, Microsoft kept the major version number as 6 in releases following Vista,[52] but changed it later to 10 in Windows 10.[45] The build number is an internal identifier used by Microsoft's developers and beta testers.
Starting withWindows 8.1, Microsoft changed the Version API Helper functions' behavior. If an application is not manifested for Windows 8.1 or later, the API will always return version 6.2, which is the version number ofWindows 8.[53][54] This is because themanifest feature was introduced with Windows 8.1,[55] to replace GetVersion and related functions.[56]
Supported platforms
32-bit platforms
In order to preventIntel x86-specific code from slipping into the operating system, due to developers being 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 theIntel i860-basedDazzle system and, later, the MIPS R4000-basedJazz platform. Both systems were designed internally at Microsoft.[57]
Windows NT 3.1 was released for Intel x86PC compatible andPC-98 platforms, and forDEC Alpha andARC-compliantMIPS platforms. Windows NT 3.51 added support for thePowerPC processor in 1995, specificallyPReP-compliant systems such as theIBM ThinkPad Power Series laptops andMotorola PowerStack series; but despite meetings betweenMichael Spindler and Bill Gates, not on thePower Macintosh as the PReP compliant Power Macintosh project failed to ship.
Intergraph Corporation ported Windows NT to itsClipper architecture and later announced an intention to port Windows NT 3.51 toSun Microsystems'SPARC architecture,[58] in conjunction with the company's planned introduction of UltraSPARC models in 1995,[59] but neither version was sold to the public as a retail product.
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 third parties (Motorola, Intergraph, etc.) have few, if any, publicly available updates.
Windows NT 4.0 was the last major release to support Alpha, MIPS, or PowerPC, though development of Windows 2000 for Alpha continued until August 1999, whenCompaq stopped support for Windows NT on that architecture; and then three days later Microsoft also canceled their AlphaNT program,[60] even though the Alpha NT 5 (Windows 2000) release had reachedRC1 status.[61]
On January 5, 2011, Microsoft announced that the next major version of the Windows NT family will include support for theARM architecture. Microsoft demonstrated a preliminary version of Windows (version 6.2.7867) running on an ARM-based computer at the 2011Consumer Electronics Show.[62] This eventually led to the commercial release of theWindows 8-derivedWindows RT on October 26, 2012, and the use of Windows NT, rather than Windows CE, inWindows Phone 8.
Windows 11 is the first non-server version of Windows NT that does not support 32-bit platforms.[67][68]
64-bit platforms
The64-bit versions of Windows NT were originally intended to run onItanium andDEC Alpha; the latter was used internally at Microsoft during early development of 64-bit Windows.[69][70] This continued for some time after Microsoft publicly announced that it was cancelling plans to ship 64-bit Windows for Alpha.[71] Because of this, Alpha versions of Windows NT are 32-bit only.
WhileWindows 2000 only supports IntelIA-32 (32-bit), Windows XP, Server 2003, Server 2008 and Server 2008 R2 each have one edition dedicated to Itanium-based systems.[72][73][74] In comparison with Itanium, Microsoft adoptedx64 on a greater scale: every version of Windows sinceWindows XP (which has adedicated x64 edition)[75] has x64 editions.[72][76]
The first version of Windows NT to support ARM64 devices with Qualcomm processors wasWindows 10, version 1709.[77] This is a full version of Windows, rather than the cut-downWindows RT.
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, a tenfold increase in free disk space alone over the previous version, and the 2021 10.0 (11) release which excludes most systems built before 2018.
^Though Windows Vista support ended in 2017 and there was never a third Service Pack, the build number change occurs when the user opts to install KB4489887 update (released for Windows Server 2008 in 2019) on their system.
^"28 – OS/2 Compatibility",MS Windows NT 4 Workstation (resource kit), Microsoft, archived fromthe original on March 3, 2016, retrievedNovember 24, 2010
^Mohr, Jim (December 1, 1999)."Windows NT Basics".Supporting Windows NT and 2000 Workstation and Server. Prentice Hall.ISBN978-0-13-083068-5.Archived from the original on March 6, 2024. RetrievedNovember 29, 2023.The technique that Windows NT uses is called a 'microkernel' and was influenced by the Mach microkernel developed at Carnegie Mellon University.
^Finnel, Lynn (2000).MCSE Exam 70-215, Microsoft Windows 2000 Server. Microsoft Press. Chapter 1: Introduction to Microsoft Windows 2000, pp. 7–18.ISBN1-57231-903-8.
^Trinder, Garry (February 17, 2006)."The Xbox Operating System".Xbox Engineering. MSDN.Archived from the original on November 2, 2018. RetrievedOctober 31, 2018.
^Chen, Raymond (August 2008)."Building on the Past". Windows Confidential.TechNet Magazine. Microsoft.Archived from the original on January 3, 2024. RetrievedNovember 30, 2023.
^Thurott, Paul (June 21, 2000)."Windows 2000 Reportedly Returning to Alpha Platform".Archived from the original on January 3, 2018. RetrievedJanuary 2, 2018.UPDATE: Compaq has apparently denied that any work is being done on Windows 2000/64 for the Alpha.
