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. It was intended to complement consumer versions of Windows that were based on MS-DOS. NT was the first fully 32-bit version of Windows, whereas its consumer-oriented counterparts, Windows 3.1x and Windows 9x, were 16-bit/32-bit hybrids. Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows Home Server, and Windows Server 2008 are based upon the Windows NT system, although they are not branded as Windows NT.
Windows NT 3.1 was the first version of Windows to utilize 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 in supervisor mode, 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 full preemptive multitasking kernel could interrupt running tasks to schedule other tasks, without relying on user programs to voluntarily give up control of the CPU, as in Windows 3.1.
Notably, in Windows NT 3.x, several I/O driver subsystems, such as video and printing, were user-mode subsystems. In Windows NT 4, the video, server and printer spooler subsystems were integrated into the kernel. Windows NT's first GUI was strongly influenced by (and programmatically compatible with) that from Windows 3.1; Windows NT 4's interface was redesigned to match that of the brand new Windows 95, moving from the Program Manager to the Start Menu/Taskbar design.
NTFS, a journaled, secure file system, was created for NT. NT also allows for other installable file systems, and with versions 3.1 and 3.51, NT could also be installed on DOS's FAT or OS/2's HPFS file systems. Later versions could be installed on a FAT partition gaining speed at the expense of security, but this option is no longer present in Windows Vista.
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 (Hardware Abstraction Layer).
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 one of the earliest operating systems to use Unicode internally.
|Version||Marketing name||Editions||Release date||RTM build|
|NT 3.1||Windows NT 3.1||Workstation (named just Windows NT), Advanced Server||27 July 1993||528|
|NT 3.5||Windows NT 3.5||Workstation, Server||21 September 1994||807|
|NT 3.51||Windows NT 3.51||Workstation, Server||30 May 1995||1057|
|NT 4.0||Windows NT 4.0||Workstation, Server, Server Enterprise Edition, Terminal Server, Embedded||29 July 1996||1381|
|NT 5.0||Windows 2000||Professional, Server, Advanced Server, Datacenter Server||17 February 2000||2195|
|NT 5.1||Windows XP||Home, Professional, 64-bit Edition (Itanium), Media Center (original, 2003, 2004 & 2005), Tablet PC (original and 2005), Starter, Embedded, Home N, Professional N||25 October 2001||2600|
|NT 5.1||Windows Fundamentals for Legacy PCs||N/A||8 July 2006||2600|
|NT 5.2||Windows XP||64-bit Edition Version 2003 (Itanium)||28 March 2003||3790|
|NT 5.2||Windows Server 2003||Standard, Enterprise, Datacenter, Web, Storage, Small Business Server, Compute Cluster||24 April 2003||3790|
|NT 5.2||Windows XP||Professional x64 Edition||25 April 2005||3790|
|NT 5.2||Windows Home Server||N/A||16 July 2007||3790|
|NT 6.0||Windows Vista||Starter, Home Basic, Home Premium, Business, Enterprise, Ultimate, Home Basic N, Business N|| Business: 30 November 2006|
Consumer: 30 January 2007
|NT 6.0||Windows Server 2008||Standard, Enterprise, Datacenter, Web, Storage, Small Business Server||27 February 2008||6001|
|NT 6.1||Windows 7 (working title, formerly codenamed Blackcomb, later Vienna)||TBA||3 June 2009||Unknown|
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. There were also some issues related to Novell IPX protocol licensing, which was apparently limited to 3.1 versions of Windows software.
The NT version number is no longer used for marketing purposes, but is still used internally, and said to reflect the degree of changes to the core of the operating system. The build number is an internal figure used by Microsoft's developers and beta testers.
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 Intel i860-based Dazzle system and, later, the MIPS R4000-based Jazz platform. Both systems were designed internally at Microsoft.
Windows NT 3.1 was released for Intel x86 PC compatible, DEC Alpha, and ARC-compliant MIPS platforms. Windows NT 3.51 added support for the PowerPC processor in 1995, specifically PReP-compliant systems such as the IBM Power Series desktops/laptops and Motorola PowerStack series; but despite meetings between Michael Spindler and Bill Gates, significantly not on the Power Macintosh.
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, when Compaq stopped support for Windows NT on that architecture; and then three days later Microsoft also canceled their AlphaNT program, even though the Alpha NT 5 (Windows 2000) release had reached RC2 (build 2128).
Released versions of NT for Alpha were 32-bit only. The 64 bit port of Windows was originally intended to run on Itanium as well as on Alpha, and Alpha hardware was accordingly used internally at Microsoft during early development of 64-bit Windows. This continued for some time after Microsoft publicly announced that it was cancelling plans to ship 64-bit Windows for Alpha, because Itanium hardware was not yet available for development.
Limited Editions of Windows 2000 Advanced Server and Datacenter Server, Windows XP 64-Bit, and Windows Server 2003 Enterprise and Datacenter support Intel's IA-64 processors. As of 25 April 2005 Microsoft had released four editions for 'x64' (see x86-64 architecture): Windows XP Professional x64 Edition, Windows Server 2003 Standard x64 Edition, Windows Server 2003 Enterprise x64 Edition, and Windows Server 2003 Datacenter x64 Edition.
|NT version||CPU||RAM||Free disk space|
|NT 3.51 Workstation||386, 25 MHz||8 MB||90 MB|
|NT 4.0 Workstation||486, 33 MHz||12 MB||110 MB|
|2000 Professional||Pentium, 133 MHz||32 MB||650 MB|
|XP||Pentium MMX, 233 MHz||64 MB||1.5 GB|
|Fundamentals for Legacy PCs||Pentium MMX, 233 MHz||64 MB||610 MB|
|Vista||Pentium III, 800 MHz||512 MB||15 GB|
The project's earlier name was NT OS/2. 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, reveal that the letters were expanded to 'New Technology' for marketing purposes but no longer carry any specific meaning.
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.
The letters were dropped from the name of Windows 2000, though literature contained the phrase 'Built on NT technology' and the system folder retained the WINNT designation. 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 fully achieved until the introduction of Windows XP.