History of Microsoft Windows
Encyclopedia
In 1983, Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 announced the development of Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

, a graphical user interface
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...

 (GUI) for its own operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 (MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

), which had shipped for IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...

 and compatible computers since 1981. The product line has changed from a GUI product to a modern operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 over two families of design, each with its own codebase
Codebase
The term codebase, or code base, is used in software development to mean the whole collection of source code used to build a particular application or component. Typically, the codebase includes only human-written source code files, and not, e.g., source code files generated by other tools or...

 and default file system.

The 3.x and 4.x family includes Windows 3.11, Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...

, Windows 98
Windows 98
Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...

, and Windows Me
Windows Me
Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....

. Windows for Workgroups 3.11 achieved the breakthrough from 16- to 32-bit networking and 32-bit disk access. Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...

 completed the migration to 32-bit code and started an entirely new user interface, most of which is still used today.

Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...

 family started with NT 3.1 in 1993. Modern Windows operating system versions are based on the newer Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...

 kernel that was originally intended for OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...

. Windows runs on IA-32
IA-32
IA-32 , also known as x86-32, i386 or x86, is the CISC instruction-set architecture of Intel's most commercially successful microprocessors, and was first implemented in the Intel 80386 as a 32-bit extension of x86 architecture...

, x86-64
X86-64
x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...

, and Itanium
Itanium
Itanium is a family of 64-bit Intel microprocessors that implement the Intel Itanium architecture . Intel markets the processors for enterprise servers and high-performance computing systems...

 processors. Microsoft is also working to bring Windows NT onto ARM in the next release of Windows. Earlier versions also ran on the i860
Intel i860
The Intel i860 was a RISC microprocessor from Intel, first released in 1989. The i860 was one of Intel's first attempts at an entirely new, high-end instruction set since the failed Intel i432 from the 1980s...

, Alpha
DEC Alpha
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computer instruction set architecture developed by Digital Equipment Corporation , designed to replace the 32-bit VAX complex instruction set computer ISA and its implementations. Alpha was implemented in microprocessors...

, MIPS
MIPS architecture
MIPS is a reduced instruction set computer instruction set architecture developed by MIPS Technologies . The early MIPS architectures were 32-bit, and later versions were 64-bit...

, Fairchild
Fairchild Semiconductor
Fairchild Semiconductor International, Inc. is an American semiconductor company based in San Jose, California. Founded in 1957, it was a pioneer in transistor and integrated circuit manufacturing...

 Clipper
Clipper architecture
The Clipper architecture is a 32-bit RISC-like instruction set architecture designed by Fairchild Semiconductor. The architecture never enjoyed much market success, and the only computer manufacturers to create major product lines using Clipper processors were Intergraph and High Level Hardware...

, and PowerPC
PowerPC
PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...

 architectures. Some work was done to port it to the SPARC
SPARC
SPARC is a RISC instruction set architecture developed by Sun Microsystems and introduced in mid-1987....

 architecture.

The NT kernel borrows many techniques from VMS
OpenVMS
OpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is a computer server operating system that runs on VAX, Alpha and Itanium-based families of computers. Contrary to what its name suggests, OpenVMS is not open source software; however, the source listings are available for purchase...

. With Windows NT 4.0 in 1996, the shell
Shell (computing)
A shell is a piece of software that provides an interface for users of an operating system which provides access to the services of a kernel. However, the term is also applied very loosely to applications and may include any software that is "built around" a particular component, such as web...

 changed from Program Manager to Explorer.

Windows 1.0 and Windows 2.0

The first independent version of Microsoft Windows, version 1.0, released on 20 November 1985, achieved little popularity. It was originally going to be called "Interface Manager" but Rowland Hanson, the head of marketing at Microsoft, convinced the company that the name Windows would be more appealing to consumers.
Windows 1.0 was not a complete operating system, but rather an "operating environment" that extended MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

, and shared the latter's inherent flaws and problems.

The first version of Microsoft Windows included a simple graphics painting program called Windows Paint; Windows Write
Windows Write
Microsoft Write is a basic word processor that came with Microsoft Windows 1.0, Windows 2.0, and the Windows 3.x series. Throughout its lifespan it was minimally updated, and is comparable to early versions of MacWrite...

, a simple word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....

; an appointment "calendar"; a "cardfiler"; a "notepad"; a "clock"; a "control panel
Control panel (computer)
Many computer user interfaces use a control panel metaphor to give the user control of software and hardware features.-Computer History:The term control panel was used for the plugboards in unit record equipment and in the early computers of the 1940s and '50s...

"; a "computer terminal
Computer terminal
A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system...

"; "Clipboard
Clipboard (software)
The clipboard is a software facility that can be used for short-term data storage and/or data transfer between documents or applications, via copy and paste operations...

"; and RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...

 driver. It also included the MS-DOS Executive and a game called Reversi
Reversi
Reversi is a board game involving abstract strategy and played by two players on a board with 8 rows and 8 columns and a set of distinct pieces for each side. Pieces typically are disks with a light and a dark face, each face belonging to one player...

.

Microsoft had worked with Apple Computer to develop several Desk Accessories
Desk Accessory
A desk accessory is a small helper-type application that can be run concurrently with any other application on the system. Early examples, such as SideKick and Macintosh desk accessories, used special programming models to provide a small degree of multitasking on a system that initially did not...

 and other minor pieces of software that were included with early Macintosh
Macintosh
The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

 system software.
As part of the related business negotiations, Microsoft had licensed certain aspects of the Macintosh user interface from Apple; in later litigation, a district court summarized these aspects as "screen displays".
In the development of Windows 1.0, Microsoft intentionally limited its borrowing of certain GUI elements from the Macintosh user interface, to comply with its license.

For example, windows were only displayed "tiled" on the screen; that is, they could not overlap or overlie one another. There was no trash can icon with which to delete files, since Apple claimed ownership of the rights to that paradigm.

Microsoft Windows version 2 came out on 9 December 1987, and proved slightly more popular than its predecessor.
Much of the popularity for Windows 2.0
Windows 2.0
Windows 2.0 is a 16-bit Microsoft Windows GUI-based operating environment that was released on December 9, 1987 and is the successor to Windows 1.0. With Windows 2.1x in 1988, Windows 2.0 was supplemented by Windows/286 and Windows/386...

 came by way of its inclusion as a "run-time version" with Microsoft's new graphical applications, Excel
Microsoft Excel
Microsoft Excel is a proprietary commercial spreadsheet application written and distributed by Microsoft for Microsoft Windows and Mac OS X. It features calculation, graphing tools, pivot tables, and a macro programming language called Visual Basic for Applications...

 and Word for Windows
Microsoft Word
Microsoft Word is a word processor designed by Microsoft. It was first released in 1983 under the name Multi-Tool Word for Xenix systems. Subsequent versions were later written for several other platforms including IBM PCs running DOS , the Apple Macintosh , the AT&T Unix PC , Atari ST , SCO UNIX,...

. They could be run from MS-DOS, executing Windows for the duration of their activity, and closing down Windows upon exit.

Microsoft Windows received a major boost around this time when Aldus
Aldus
Aldus Corporation, named after the 15th-century Venetian printer Aldus Manutius, was the inventor of the groundbreaking PageMaker software, a program that is generally credited with creating the desktop publishing field. The company was founded by Jeremy Jaech, Mark Sundstrom, Mike Templeman,...

 PageMaker
Adobe PageMaker
PageMaker was one of the first desktop publishing programs, introduced in 1985 by Aldus Corporation, initially for the then-new Apple Macintosh and in 1987 for PCs running Windows 1.0....

 appeared in a Windows version, having previously run only on Macintosh.
Some computer historians date this, the first appearance of a significant and non-Microsoft application for Windows, as the start of the success of Windows.

Versions 2.0x used the real-mode
Real mode
Real mode, also called real address mode, is an operating mode of 80286 and later x86-compatible CPUs. Real mode is characterized by a 20 bit segmented memory address space and unlimited direct software access to all memory, I/O addresses and peripheral hardware...

 memory
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....

 model, which confined it to a maximum of 1 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...

 of memory.
In such a configuration, it could run under another multitasker like DESQview
DESQview
DESQview was a text mode multitasking program developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s...

, which used the 286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...

 protected mode
Protected mode
In computing, protected mode, also called protected virtual address mode, is an operational mode of x86-compatible central processing units...

.
Later, two new versions were released: Windows/286 2.1 and Windows/386 2.1. Like prior versions of Windows, Windows/286 2.1 used the real-mode memory model, but was the first version to support the High Memory Area. Windows/386 2.1 had a protected mode kernel with LIM-standard EMS emulation
Hardware emulation
In integrated circuit design, hardware emulation is the process of imitating the behavior of one or more pieces of hardware with another piece of hardware, typically a special purpose emulation system. The emulation model is usually based on RTL source code, which is compiled into the format...

, the predecessor to XMS
Extended memory
In DOS memory management, extended memory refers to memory above the first megabyte of address space in an IBM PC or compatible with an 80286 or later processor. The term is mainly used under the DOS and Windows operating systems...

 which would finally change the topology of IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 PC computing. All Windows and DOS-based applications at the time were real mode, running over the protected mode kernel by using the virtual 8086
Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...

 mode, which was new with the 80386 processor.

Version 2.03, and later 3.0, faced challenges from Apple over its overlapping windows and other features Apple charged mimicked the ostensibly copyrighted "look and feel" of its operating system and "embodie[d] and generated a copy of the Macintosh" in its OS. Judge William Schwarzer
William Schwarzer
William W. Schwarzer is a United States federal judge serving on the U.S. District Court for the Northern District of California.Born in Berlin, Germany, Schwarzer served in the United States Army during World War II, beginning in 1943. He attained the rank of Second Lietuenant, and was...

 dropped all but 10 of Apple's 189 claims of copyright infringement, and ruled that most of the remaining 10 were over uncopyrightable ideas.

Success with Windows 3.0

Microsoft Windows scored a significant success with Windows 3.0, released in 1990. In addition to improved capabilities given to native applications, Windows also allowed users to better multitask
Computer multitasking
In computing, multitasking is a method where multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for...

 older MS-DOS based software compared to Windows/386, thanks to the introduction of virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...

.

Windows 3.0's user interface was finally a serious competitor to the user interface of the Macintosh
Macintosh
The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

 computer. PCs had improved graphics by this time, due to VGA video cards, and the protected/enhanced mode allowed Windows applications to use more memory in a more painless manner than their DOS counterparts could. Windows 3.0
Windows 3.0
Windows 3.0, a graphical environment, is the third major release of Microsoft Windows, and was released on 22 May 1990. It became the first widely successful version of Windows and a rival to Apple Macintosh and the Commodore Amiga on the GUI front...

 could run in real, standard, or 386 enhanced modes, and was compatible with any Intel processor from the 8086
Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...

/8088
Intel 8088
The Intel 8088 microprocessor was a variant of the Intel 8086 and was introduced on July 1, 1979. It had an 8-bit external data bus instead of the 16-bit bus of the 8086. The 16-bit registers and the one megabyte address range were unchanged, however...

 up to the 80286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...

 and 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...

. This was the first version to run Windows programs in protected mode, although the 386 enhanced mode kernel was an enhanced version of the protected mode kernel in Windows/386.

A "multimedia" version, Windows 3.0 with Multimedia Extensions 1.0, was released in October 1991. This was bundled with "multimedia upgrade kits", comprising a CD-ROM drive and a sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...

, such as the Creative Labs Sound Blaster Pro. This version was the precursor to the multimedia features available in Windows 3.1 and later, and was part of Microsoft's specification for the Multimedia PC
Multimedia PC
The Multimedia PC, or MPC, was a recommended configuration for a PC with a CD-ROM drive. The standard was set and named by the "Multimedia PC Marketing Council", which was a working group of the Software Publishers Association . The MPMC comprised companies including Microsoft, Creative Labs,...

.

The features listed above and growing market support from application software developers made Windows 3.0 wildly successful, selling around 10 million copies in the two years before the release of version 3.1. Windows 3.0 became a major source of income for Microsoft, and led the company to revise some of its earlier plans. It was discontinued on 31 December 2001.

A step sideways: OS/2

During the mid to late 1980s, Microsoft and IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 had cooperatively been developing OS/2
OS/2
OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...

 as a successor to DOS. OS/2 would take full advantage of the aforementioned protected mode of the Intel 80286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...

 processor and up to 16 MB of memory. OS/2 1.0, released in 1987, supported swapping and multitasking and allowed running of DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

 executables.

A GUI
Graphical user interface
In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...

, called the Presentation Manager (PM), was not available with OS/2 until version 1.1, released in 1988. Its API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...

 was incompatible with Windows. (Among other things, Presentation Manager placed X,Y coordinate 0,0 at the bottom left of the screen like Cartesian coordinates, while Windows put 0,0 at the top left of the screen like most other computer window systems.) Version 1.2, released in 1989, introduced a new file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

, HPFS, to replace the FAT
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...

 file system.

By the early 1990s, conflicts developed in the Microsoft/IBM relationship. They cooperated with each other in developing their PC operating systems, and had access to each others' code. Microsoft wanted to further develop Windows, while IBM desired for future work to be based on OS/2. In an attempt to resolve this tension, IBM and Microsoft agreed that IBM would develop OS/2 2.0, to replace OS/2 1.3 and Windows 3.0, while Microsoft would develop a new operating system, OS/2 3.0, to later succeed OS/2 2.0.

This agreement soon however fell apart, and the Microsoft/IBM relationship was terminated. IBM continued to develop OS/2, while Microsoft changed the name of its (as yet unreleased) OS/2 3.0 to Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...

. Both retained the rights to use OS/2 and Windows technology developed up to the termination of the agreement; Windows NT, however, was to be written anew, mostly independently (see below).

After an interim 1.3 version to fix up many remaining problems with the 1.x series, IBM released OS/2 version 2.0 in 1992. This was a major improvement: it featured a new, object-oriented GUI, the Workplace Shell (WPS), that included a desktop and was considered by many to be OS/2's best feature. Microsoft would later imitate much of it in Windows 95. Version 2.0 also provided a full 32-bit API, offered smooth multitasking and could take advantage of the 4 gigabytes of address space provided by the Intel 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...

. Still, much of the system had 16-bit code internally which required, among other things, device drivers to be 16-bit code also. This was one of the reasons for the chronic shortage of OS/2 drivers for the latest devices. Version 2.0 could also run DOS and Windows 3.0 programs, since IBM had retained the right to use the DOS and Windows code as a result of the breakup.

Windows 3.1 and NT 3.x

In response to the impending release of OS/2 2.0, Microsoft developed Windows 3.1, which included several minor improvements to Windows 3.0 (such as display of TrueType
TrueType
TrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...

 scalable fonts, developed jointly with Apple), but primarily consisted of bugfixes and multimedia support. It also excluded support for Real mode, and only ran on an 80286 or better processor. Later Microsoft also released Windows 3.11, a touch-up to Windows 3.1 which included all of the patches and updates that followed the release of Windows 3.1 in 1992. Around the same time, Microsoft released Windows for Workgroups (WfW), which was available both as an add-on for existing Windows 3.1 installations and in a version that included the base Windows environment and the networking extensions all in one package. Windows for Workgroups included improved network drivers and protocol stacks, and support for peer-to-peer networking. One optional download for WfW was the "Wolverine" TCP/IP protocol stack, which allowed for easy access to the Internet through corporate networks. There were two versions of Windows for Workgroups, WfW 3.1 and WfW 3.11. Unlike prior versions, Windows for Workgroups 3.11 ran in 386 enhanced mode only, and needs at least an 80386SX processor.

All these versions continued version 3.0's impressive sales pace. Even though the 3.1x series still lacked most of the important features of OS/2, such as long file names, a desktop, or protection of the system against misbehaving applications, Microsoft quickly took over the OS and GUI markets for the IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...

. The Windows API
Windows API
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces available in the Microsoft Windows operating systems. It was formerly called the Win32 API; however, the name "Windows API" more accurately reflects its roots in 16-bit Windows and its support on...

 became the de-facto standard for consumer software.

Meanwhile, Microsoft continued to develop Windows NT. The main architect of the system was Dave Cutler
Dave Cutler
David Neil Cutler, Sr. is an American software engineer, designer and developer of several operating systems including RSX-11M, VMS and VAXELN at Digital Equipment Corporation and Windows at Microsoft.- Personal history :...

, one of the chief architects of VMS at Digital Equipment Corporation
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

 (later acquired by Compaq
Compaq
Compaq Computer Corporation is a personal computer company founded in 1982. Once the largest supplier of personal computing systems in the world, Compaq existed as an independent corporation until 2002, when it was acquired for US$25 billion by Hewlett-Packard....

, now part of Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

). Microsoft hired him in August 1988 to create a successor to OS/2, but Cutler created a completely new system instead. Cutler had been developing a follow-on to VMS at DEC
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

 called Mica, and when DEC dropped the project he brought the expertise and around 20 engineers with him to Microsoft. DEC also believed he brought Mica's code to Microsoft and sued. Microsoft eventually paid US$150 million and agreed to support DEC's Alpha
DEC Alpha
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computer instruction set architecture developed by Digital Equipment Corporation , designed to replace the 32-bit VAX complex instruction set computer ISA and its implementations. Alpha was implemented in microprocessors...

 CPU chip in NT.

Windows NT 3.1 (Microsoft marketing wanted Windows NT to appear to be a continuation of Windows 3.1) arrived in Beta form to developers at the July 1992 Professional Developers Conference
Professional Developers Conference
Microsoft's Professional Developers Conference is a conference for software developers, normally Windows developers.It covers new and upcoming technology from Microsoft, and so only occurs in the years when there is something new to talk about...

 in San Francisco. Microsoft announced at the conference its intentions to develop a successor to both Windows NT and Windows 3.1's replacement (Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...

, codenamed Chicago), which would unify the two into one operating system. This successor was codenamed Cairo
Cairo (operating system)
Cairo was the code name for a project at Microsoft from 1991 to 1996. Its charter was to build technologies for a next generation operating system that would fulfill Bill Gates' vision of "information at your fingertips." Cairo never shipped, although portions of its technologies have since...

. In hindsight, Cairo was a much more difficult project than Microsoft had anticipated and, as a result, NT and Chicago would not be unified until Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...

—albeit Windows 2000
Windows 2000
Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...

, oriented to business, had already unified most of the system’s bolts and gears, it was XP that was sold to home consumers like Windows 95 and came to be viewed as the final unified OS. Parts of Cairo have still not made it into Windows as of 2009 - specifically, the WinFS
WinFS
WinFS is the code name for a cancelled data storage and management system project based on relational databases, developed by Microsoft and first demonstrated in 2003 as an advanced storage subsystem for the Microsoft Windows operating system, designed for persistence and management of...

 file system, which was the much touted Object File System of Cairo. Microsoft announced that they have discontinued the separate release of WinFS for Windows XP and Windows Vista and will gradually incorporate the technologies developed for WinFS in other products and technologies, notably Microsoft SQL Server
Microsoft SQL Server
Microsoft SQL Server is a relational database server, developed by Microsoft: It is a software product whose primary function is to store and retrieve data as requested by other software applications, be it those on the same computer or those running on another computer across a network...

.

Driver support was lacking due to the increased programming difficulty in dealing with NT's superior hardware abstraction model. This problem plagued the NT line all the way through Windows 2000. Programmers complained that it was too hard to write drivers for NT, and hardware developers were not going to go through the trouble of developing drivers for a small segment of the market. Additionally, although allowing for good performance and fuller exploitation of system resources, it was also resource-intensive on limited hardware, and thus was only suitable for larger, more expensive machines.

However, these same features made Windows NT perfect for the LAN
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

 server market (which in 1993 was experiencing a rapid boom, as office networking was becoming common). NT also had advanced network connectivity options and NTFS
NTFS
NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7....

, an efficient file system. Windows NT version 3.51 was Microsoft's entry into this field, and took away market share from Novell (the dominant player) in the following years.

One of Microsoft's biggest advances initially developed for Windows NT was a new 32-bit API, to replace the legacy 16-bit Windows API
Windows API
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces available in the Microsoft Windows operating systems. It was formerly called the Win32 API; however, the name "Windows API" more accurately reflects its roots in 16-bit Windows and its support on...

. This API was called Win32, and from then on Microsoft referred to the older 16-bit API as Win16. The Win32 API had three main implementations: one for Windows NT, one for Win32s
Win32s
Win32s is a 32-bit application runtime environment for the Microsoft Windows 3.1 and 3.11 operating systems. It allowed some 32-bit applications to run on the 16-bit operating system using call thunks.- Concept and Characteristics :...

 (which was a subset of Win32 which could be used on Windows 3.1 systems), and one for Chicago. Thus Microsoft sought to ensure some degree of compatibility between the Chicago design and Windows NT, even though the two systems had radically different internal architectures. Windows NT was the first Windows operating system based on a hybrid kernel.

Windows 95

After Windows 3.11
Windows 3.1x
Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0...

, Microsoft began to develop a new consumer oriented version of the operating system codenamed Chicago. Chicago was designed to have support for 32-bit preemptive multitasking like OS/2 and Windows NT, although a 16-bit kernel would remain for the sake of backward compatibility. The Win32 API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...

 first introduced with Windows NT was adopted as the standard 32-bit programming interface, with Win16 compatibility being preserved through a technique known as "thunking
Thunk (compatibility mapping)
Thunk refers to the creation of a 16-bit virtual DOS machine within a 32-bit operating platform so that there is backward compatibility for applications using older code or system calls.-OS/2 & Windows 16-bit address hack:...

". A new GUI was not originally planned as part of the release, although elements of the Cairo user interface were borrowed and added as other aspects of the release (notably Plug and Play) slipped.

Microsoft did not change all of the Windows code to 32-bit; parts of it remained 16-bit (albeit not directly using real mode
Real mode
Real mode, also called real address mode, is an operating mode of 80286 and later x86-compatible CPUs. Real mode is characterized by a 20 bit segmented memory address space and unlimited direct software access to all memory, I/O addresses and peripheral hardware...

) for reasons of compatibility, performance, and development time. Additionally it was necessary to carry over design decisions from earlier versions of Windows for reasons of backwards compatibility, even if these design decisions no longer matched a more modern computing environment. These factors eventually began to impact the operating system's efficiency and stability.

Microsoft marketing adopted Windows 95
Windows 95
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...

 as the product name for Chicago when it was released on 24 August 1995. Microsoft had a double gain from its release: first, it made it impossible for consumers to run Windows 95 on a cheaper, non-Microsoft DOS; secondly, although traces of DOS were never completely removed from the system and MS DOS 7 would be loaded briefly as a part of the booting
Booting
In computing, booting is a process that begins when a user turns on a computer system and prepares the computer to perform its normal operations. On modern computers, this typically involves loading and starting an operating system. The boot sequence is the initial set of operations that the...

 process, Windows 95 applications ran solely in 386 enhanced mode, with a flat 32-bit address space and virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...

. These features make it possible for Win32 applications to address up to 2 gigabyte
Gigabyte
The gigabyte is a multiple of the unit byte for digital information storage. The prefix giga means 109 in the International System of Units , therefore 1 gigabyte is...

s of virtual RAM (with another 2 GB reserved for the operating system), and in theory prevented them from inadvertently corrupting the memory space of other Win32 applications. In this respect the functionality of Windows 95 moved closer to Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...

, although Windows 95/98/ME did not support more than 512 megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...

s of physical RAM without obscure system tweaks.

IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 continued to market OS/2, producing later versions in OS/2 3.0 and 4.0 (also called Warp). Responding to complaints about OS/2 2.0's high demands on computer hardware, version 3.0 was significantly optimized both for speed and size. Before Windows 95 was released, OS/2 Warp 3.0 was even shipped preinstalled with several large German hardware vendor chains. However, with the release of Windows 95, OS/2 began to lose market share.

It is probably impossible to choose one specific reason why OS/2 failed to gain much market share. While OS/2 continued to run Windows 3.1 applications, it lacked support for anything but the Win32s
Win32s
Win32s is a 32-bit application runtime environment for the Microsoft Windows 3.1 and 3.11 operating systems. It allowed some 32-bit applications to run on the 16-bit operating system using call thunks.- Concept and Characteristics :...

 subset of Win32 API (see above). Unlike with Windows 3.1, IBM did not have access to the source code for Windows 95 and was unwilling to commit the time and resources to emulate the moving target of the Win32 API. IBM later introduced OS/2 into the United States v. Microsoft
United States v. Microsoft
United States v. Microsoft was a set of civil actions filed against Microsoft Corporation pursuant to the Sherman Antitrust Act of 1890 Section 1 and 2 on May 8, 1998 by the United States Department of Justice and 20 U.S. states. Joel I. Klein was the lead prosecutor...

 case, blaming unfair marketing tactics on Microsoft's part.

Microsoft went on to release five different versions of Windows 95:
  • Windows 95 - original release
  • Windows 95 A - included Windows 95 OSR1 slipstreamed
    Slipstream (computing)
    In computer jargon, to slipstream updates, patches or service packs means to integrate them into the installation files of their original software, so that the resulting files will allow a direct installation of the updated software....

     into the installation.
  • Windows 95 B - (OSR2) included several major enhancements, Internet Explorer
    Internet Explorer
    Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...

     (IE) 3.0 and full FAT32
    File Allocation Table
    File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...

     file system support.
  • Windows 95 B USB - (OSR2.1) included basic USB
    Universal Serial Bus
    USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....

     support.
  • Windows 95 C - (OSR2.5) included all the above features, plus IE 4.0. This was the last 95 version produced.


OSR2, OSR2.1, and OSR2.5 were not released to the general public; rather, they were available only to OEMs
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...

 that would preload the OS onto computers. Some companies sold new hard drives with OSR2 preinstalled (officially justifying this as needed due to the hard drive's capacity).

The first Microsoft Plus!
Microsoft Plus!
Microsoft Plus! was a commercial operating system enhancement product by Microsoft. The last edition is the Plus! SuperPack, which includes an assortment of screensavers, themes, and games, as well as multimedia applications...

 add-on pack was sold for Windows 95.

Windows NT 4.0

Windows NT 4.0
Windows NT 4.0
Windows NT 4.0 is a preemptive, graphical and business-oriented operating system designed to work with either uniprocessor or symmetric multi-processor computers. It was the next release of Microsoft's Windows NT line of operating systems and was released to manufacturing on 31 July 1996...

 was the successor of 3.51
Windows NT 3.51
Windows NT 3.51 is the third release of Microsoft's Windows NT line of operating systems. It was released on 30 May 1995, nine months after Windows NT 3.5. The release provided two notable feature improvements; firstly NT 3.51 was the first of a short-lived outing of Microsoft Windows on the...

 (1995) and 3.5
Windows NT 3.5
Windows NT 3.5 is the second release of the Microsoft Windows NT operating system. It was released on 21 September 1994.One of the primary goals during Windows NT 3.5's development was to increase the speed of the operating system; as a result, the project was given the codename "Daytona" in...

 (1994). Microsoft released Windows NT 4.0 to manufacturing in July 1996, one year after the release of Windows 95. Major new features included the new Explorer shell from Windows 95, scalability and feature improvements to the core architecture, kernel, USER32, COM
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...

 and MSRPC
MSRPC
Microsoft RPC is a modified version of DCE/RPC. Additions include support for Unicode strings, implicit handles, inheritance of interfaces , and complex calculations in the variable-length string and structure paradigms already present in DCE/RPC.- Example :The DCE 1.0 reference implementation...

.

Windows NT 4.0 came in four versions:
  • Windows NT 4.0 Workstation
  • Windows NT 4.0 Server
  • Windows NT 4.0 Server, Enterprise Edition (includes support for 8-way SMP
    Symmetric multiprocessing
    In computing, symmetric multiprocessing involves a multiprocessor computer hardware architecture where two or more identical processors are connected to a single shared main memory and are controlled by a single OS instance. Most common multiprocessor systems today use an SMP architecture...

     and clustering
    Cluster (computing)
    A computer cluster is a group of linked computers, working together closely thus in many respects forming a single computer. The components of a cluster are commonly, but not always, connected to each other through fast local area networks...

    )
  • Windows NT 4.0 Terminal Server

Windows 98

On 25 June 1998, Microsoft released Windows 98 (codenamed Memphis). It included new hardware drivers and better support for the FAT32
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...

 file system which allows support for disk partitions larger than the 2 GB maximum accepted by Windows 95. The USB support in Windows 98 is far superior to the token, unreliable support provided by the OEM
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...

 editions of Windows 95. It also controversially integrated the Internet Explorer
Internet Explorer
Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...

 browser into the Windows GUI and Windows Explorer file manager, prompting the opening of the United States v. Microsoft
United States v. Microsoft
United States v. Microsoft was a set of civil actions filed against Microsoft Corporation pursuant to the Sherman Antitrust Act of 1890 Section 1 and 2 on May 8, 1998 by the United States Department of Justice and 20 U.S. states. Joel I. Klein was the lead prosecutor...

 case, dealing with the question of whether Microsoft was abusing its hold on the PC operating system market to unfairly compete with companies such as Netscape
Netscape
Netscape Communications is a US computer services company, best known for Netscape Navigator, its web browser. When it was an independent company, its headquarters were in Mountain View, California...

.

In 1999, Microsoft released Windows 98 Second Edition, an interim release. One of the more notable new features was the addition of Internet Connection Sharing
Internet Connection Sharing
Internet Connection Sharing is the use of a device with Internet access such as 3G cellular service, broadband via Ethernet, or other Internet gateway as an access point for other devices...

, which was a form of network address translation
Network address translation
In computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....

, allowing several machines on a LAN (Local Area Network) to share a single Internet connection. Second Edition was also much easier to use and much smoother than the first edition of Windows 98. Hardware support through device drivers was increased. Many minor problems present in the original Windows 98 were found and fixed which make it, according to many, the most stable release of Windows 9x
Windows 9x
Windows 9x is a generic term referring to a series of Microsoft Windows computer operating systems produced since 1995, which were based on the original and later modified Windows 95 kernel...

 family—to the extent that commentators used to say that Windows 98's beta version was more stable than Windows 95's final (gamma) version.

Windows 2000

Microsoft released Windows 2000 in February 2000. It has the version number Windows NT 5.0. It was successfully deployed both on the server and the workstation markets. Amongst Windows 2000's most significant new features was Active Directory
Active Directory
Active Directory is a directory service created by Microsoft for Windows domain networks. It is included in most Windows Server operating systems. Server computers on which Active Directory is running are called domain controllers....

, a near-complete replacement of the NT 4.0 Windows Server domain
Windows Server domain
A Windows domain is a collection of security principals that share a central directory database. This central database contains the user accounts and security information for...

 model, which built on industry-standard technologies like DNS
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...

, LDAP
Lightweight Directory Access Protocol
The Lightweight Directory Access Protocol is an application protocol for accessing and maintaining distributed directory information services over an Internet Protocol network...

, and Kerberos to connect machines to one another. Terminal Services
Terminal Services
Remote Desktop Services in Windows Server 2008 R2, formerly known as Terminal Services in Windows Server 2008 and previous versions, is one of the components of Microsoft Windows that allows a user to access applications and data on a remote computer over a network, using the Remote Desktop...

, previously only available as a separate edition of NT 4, was expanded to all server versions. A number of features from Windows 98 were incorporated also, such as an improved Device Manager, Windows Media Player
Windows Media Player
Windows Media Player is a media player and media library application developed by Microsoft that is used for playing audio, video and viewing images on personal computers running the Microsoft Windows operating system, as well as on Pocket PC and Windows Mobile-based devices...

, and a revised DirectX
DirectX
Microsoft DirectX is a collection of application programming interfaces for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with Direct, such as Direct3D, DirectDraw, DirectMusic, DirectPlay,...

 that made it possible for the first time for many modern games to work on the NT kernel. Windows 2000 is also the last NT-kernel Windows operating system to lack product activation
Microsoft Product Activation
Microsoft Product Activation is a form of digital rights management used by Microsoft Corporation in several of its computer software programs, most notably its Windows operating system and its Office productivity suite...

.

While Windows 2000 upgrades were available for Windows 95 and Windows 98, it was not intended for home users.

Windows 2000 was available in six editions:
  • Windows 2000 Professional
  • Windows 2000 Server
  • Windows 2000 Advanced Server
  • Windows 2000 Datacenter Server
  • Windows 2000 Advanced Server Limited Edition
  • Windows 2000 Datacenter Server Limited Edition

Windows Millennium Edition (Me)

In September 2000, Microsoft introduced Windows Me (Millennium Edition), which upgraded Windows 98 with enhanced multimedia and Internet features from Windows 2000. It also introduced the first version of System Restore, which allowed users to revert their system state to a prior "known-good" point in the case of system failure. System Restore was a notable feature that made its way into Windows XP. The first version of Windows Movie Maker
Windows Movie Maker
Windows Movie Maker is a video creating/editing software application, included in Microsoft Windows Me, XP, and Vista. It contains features such as effects, transitions, titles/credits, audio track, timeline narration, and Auto Movie. New effects and transitions can be made and existing ones can be...

 was introduced also.

Windows Me was conceived as a quick one-year project that served as a stopgap release between Windows 98 and Windows XP. Many of the new features were available from the Windows Update site
Windows Update
Windows Update is a service provided by Microsoft that provides updates for the Microsoft Windows operating system and its installed components, including Internet Explorer...

 as updates for older Windows versions, (System Restore and Windows Movie Maker were exceptions). Windows Me was criticised for stability issues, and for lacking real mode
Real mode
Real mode, also called real address mode, is an operating mode of 80286 and later x86-compatible CPUs. Real mode is characterized by a 20 bit segmented memory address space and unlimited direct software access to all memory, I/O addresses and peripheral hardware...

 DOS support, to the point of being referred to as the "Mistake Edition" or "Many Errors." Windows Me was the last operating system to be based on the Windows 9x (monolithic
Monolithic kernel
A monolithic kernel is an operating system architecture where the entire operating system is working in the kernel space and alone as supervisor mode...

) kernel and MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

.

Windows XP

In 2001, Microsoft released Windows XP (code named "Whistler"). The merging of the Windows NT/2000 and Windows 95/98/Me lines was finally achieved with Windows XP. Windows XP uses the Windows NT 5.1 kernel, marking the entrance of the Windows NT core to the consumer market, to replace the aging 16/32-bit branch. The initial release met with considerable criticism, particularly in the area of security
Information security
Information security means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification, perusal, inspection, recording or destruction....

, leading to the release of three major Service Pack
Service pack
A service pack is a collection of updates, fixes or enhancements to a software program delivered in the form of a single installable package. Many companies, such as Microsoft or Autodesk, typically release a service pack when the number of individual patches to a given program reaches a certain ...

s. Windows XP SP1 was released in September 2002, SP2 came out in August 2004 and SP3 came out in April 2008. Service Pack 2 provided significant improvements and encouraged widespread adoption of XP among both home and business users. Windows XP lasted longer as Microsoft's flagship operating system than any other version of Windows, from October 25, 2001 to January 30, 2007 when it was succeeded by Windows Vista.

Windows XP is available in a number of versions:
  • Windows XP Home Edition, for home desktops and laptop
    Laptop
    A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...

    s - lacked features such as joining Active Directory
    Active Directory
    Active Directory is a directory service created by Microsoft for Windows domain networks. It is included in most Windows Server operating systems. Server computers on which Active Directory is running are called domain controllers....

     Domain, Remote Desktop
    Terminal Services
    Remote Desktop Services in Windows Server 2008 R2, formerly known as Terminal Services in Windows Server 2008 and previous versions, is one of the components of Microsoft Windows that allows a user to access applications and data on a remote computer over a network, using the Remote Desktop...

     Server and Internet Information Services
    Internet Information Services
    Internet Information Services – formerly called Internet Information Server – is a web server application and set of feature extension modules created by Microsoft for use with Microsoft Windows. It is the most used web server after Apache HTTP Server. IIS 7.5 supports HTTP, HTTPS,...

     Server.
    • Windows XP Home Edition N, as above, but without a default installation of Windows Media Player
      Windows Media Player
      Windows Media Player is a media player and media library application developed by Microsoft that is used for playing audio, video and viewing images on personal computers running the Microsoft Windows operating system, as well as on Pocket PC and Windows Mobile-based devices...

      , as mandated by a European Union
      European Union
      The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

       ruling
  • Windows XP Professional, for business and power users contained all features in Home Edition.
    • Windows XP Professional N, as above, but without a default installation of Windows Media Player, as mandated by a European Union ruling
  • Windows XP Media Center Edition
    Windows XP Media Center Edition
    Windows XP Media Center Edition is a version of the Windows XP operating system designed to serve as a home-entertainment hub. The last version, Windows XP Media Center Edition 2005, was released in October 2004.-Versions:...

     (MCE), released in October 2002 for desktops and notebooks with an emphasis on home entertainment. Contained all features offered in Windows XP Professional and the Windows Media Center. Subsequent versions are the same but have an updated Windows Media Center.
    • Windows XP Media Center Edition 2003
    • Windows XP Media Center Edition 2004
    • Windows XP Media Center Edition 2005, released on 12 October 2004. Included Windows XP Service Pack 2, the Royale Windows Theme and joining a Windows Active Directory Domain is disabled.
  • Windows XP Tablet PC Edition, for tablet PCs
    Microsoft Tablet PC
    A Microsoft Tablet PC is a term coined by Microsoft for tablet computers conforming to a set of specifications announced in 2001 by Microsoft, for a pen-enabled personal computer, conforming to hardware specifications devised by Microsoft and running a licensed copy of Windows XP Tablet PC Edition...

    • Windows XP Tablet PC Edition 2005
  • Windows XP Embedded, for embedded systems
  • Windows XP Starter Edition, for new computer users in developing countries
  • Windows XP Professional x64 Edition
    Windows XP Professional x64 Edition
    Microsoft Windows XP Professional x64 Edition released on April 25, 2005 is an edition of Windows XP for x86-64 personal computers. It is designed to use the expanded 64-bit memory address space provided by the x86-64 architecture....

    , released on 25 April 2005 for home and workstation systems utilizing 64-bit processors based on the x86-64
    X86-64
    x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...

     instruction set developed by AMD as AMD64; Intel calls their version Intel 64
  • Windows XP 64-bit Edition, is a version for Intel's Itanium
    Itanium
    Itanium is a family of 64-bit Intel microprocessors that implement the Intel Itanium architecture . Intel markets the processors for enterprise servers and high-performance computing systems...

     line of processors; maintains 32-bit compatibility solely through a software emulator. It is roughly analogous to Windows XP Professional in features. It was discontinued in September 2005 when the last vendor of Itanium workstations stopped shipping Itanium systems marketed as "Workstations".
    • Windows XP 64-bit Edition 2003, based on the Windows NT 5.2 codebase.

Windows Server 2003

On 25 April 2003 Microsoft launched Windows Server 2003, a notable update to Windows 2000 Server encompassing many new security
Security
Security is the degree of protection against danger, damage, loss, and crime. Security as a form of protection are structures and processes that provide or improve security as a condition. The Institute for Security and Open Methodologies in the OSSTMM 3 defines security as "a form of protection...

 features, a new "Manage Your Server
Web server
Web server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....

" wizard that simplifies configuring a machine for specific roles, and improved performance. It has the version number NT 5.2. A few services not essential for server environments are disabled by default for stability reasons, most noticeable are the "Windows Audio" and "Themes" services; Users have to enable them manually to get sound or the "Luna
Luna (theme)
Themes customize the appearance of the Windows operating system without changing its functionality ....

" look as per Windows XP. The hardware acceleration for display is also turned off by default, users have to turn the acceleration level up themselves if they trust the display card driver.

December 2005, Microsoft released Windows Server 2003 R2, which is actually Windows Server 2003 with SP1 (Service Pack
Service pack
A service pack is a collection of updates, fixes or enhancements to a software program delivered in the form of a single installable package. Many companies, such as Microsoft or Autodesk, typically release a service pack when the number of individual patches to a given program reaches a certain ...

 1) plus an add-on package.
Among the new features
Feature (software design)
The Institute of Electrical and Electronics Engineers defines the term feature in IEEE 829 as "A distinguishing characteristic of a software item ." - Feature-rich :...

 are a number of management features for branch offices, file serving, printing and company-wide identity integration.

Windows Server 2003 is available in six editions:
  • Web Edition (32-bit)
  • Standard Edition (32 and 64-bit)
  • Enterprise Edition (32 and 64-bit)
  • Datacenter Edition (32 and 64-bit)
  • Small Business Server (32-bit)
  • Storage Server (OEM channel only)


Windows XP x64 and Server 2003 x64 Editions

On 25 April 2005, Microsoft released Windows XP Professional x64 Edition and Windows Server 2003, x64 Editions in Standard, Enterprise and Datacenter SKUs. Windows XP Professional x64 Edition is an edition of Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...

 for x86-64
X86-64
x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...

 personal computers. It is designed to use the expanded 64-bit memory address space provided by the x86-64 architecture.

Windows XP Professional x64 Edition is based on the Windows Server 2003
Windows Server 2003
Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...

 codebase; with the server features removed and client features added. Both Windows Server 2003 x64 and Windows XP Professional x64 Edition use identical kernels.

Windows XP Professional x64 Edition is not to be confused with Windows XP 64-bit Edition, as the latter was designed for Intel Itanium
Itanium
Itanium is a family of 64-bit Intel microprocessors that implement the Intel Itanium architecture . Intel markets the processors for enterprise servers and high-performance computing systems...

 processors. During the initial development phases, Windows XP Professional x64 Edition was named Windows XP 64-Bit Edition for 64-Bit Extended Systems.

Windows Server 2003 R2

Windows Server 2003 R2, an update of Windows Server 2003, was released to manufacturing on 6 December 2005. It is distributed on two CDs, with one CD being the Windows Server 2003 SP1 CD. The other CD adds many optionally installable features for Windows Server 2003. The R2 update was released for all x86 and x64 versions. Windows Server 2003 R2 Enterprise Edition was not released for Itanium.

Windows Fundamentals for Legacy PCs

In July 2006, Microsoft released a thin-client version of Windows XP Service Pack 2, called Windows Fundamentals for Legacy PCs
Windows Fundamentals for Legacy PCs
Windows Fundamentals for Legacy PCs is a thin client operating system from Microsoft, based on Windows XP Embedded, but optimized for older, less powerful hardware. It was released on 8 July 2006...

 (WinFLP). It is only available to Software Assurance
Microsoft Software Assurance
Microsoft Software Assurance is a Microsoft maintenance program aimed at business users who use Microsoft Windows, Microsoft Office, and other server and desktop applications...

 customers. The aim of WinFLP is to give companies a viable upgrade option for older PCs that are running Windows 95, 98, and Me that will be supported with patches and updates for the next several years. Most user applications will typically be run on a remote machine using Terminal Services or Citrix.

Windows Home Server

Windows Home Server (codenamed Q, Quattro) is a server product based on Windows Server 2003
Windows Server 2003
Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...

, designed for consumer use. The system was announced on 7 January 2007 by Bill Gates
Bill Gates
William Henry "Bill" Gates III is an American business magnate, investor, philanthropist, and author. Gates is the former CEO and current chairman of Microsoft, the software company he founded with Paul Allen...

. Windows Home Server can be configured and monitored using a console program that can be installed on a client PC. Such features as Media Sharing, local and remote drive backup and file duplication are all listed as features.

Windows Vista

Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...

 was released on 30 November 2006 to business customers, consumer versions following on 30 January 2007. Windows Vista intended to have enhanced security by introducing a new restricted user mode called User Account Control
User Account Control
User Account Control is a technology and security infrastructure introduced with Microsoft's Windows Vista and Windows Server 2008 operating systems, with a more relaxed version also present in Windows 7 and Windows Server 2008 R2...

, replacing the "administrator-by-default" philosophy of Windows XP. One major difference between Vista and earlier versions of Windows, Windows 95 and later, is that the original start button was replaced with just the Windows icon. Vista also features new graphics features, the Windows Aero
Windows Aero
Windows Aero is the graphical user interface and the default theme in most editions of Windows Vista and Windows 7, operating systems released by Microsoft. It is also available in Windows Server 2008, but is not enabled by default. Its name is a backronym for Authentic, Energetic, Reflective and...

 GUI
Gui
Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...

, new applications (such as Windows Calendar
Windows Calendar
Windows Calendar is a calendar application that is included with Windows Vista and Windows Server 2008. It natively supports the iCalendar file format, and has the ability to publish and subscribe to web-based calendars by using HTTP and WebDAV...

, Windows DVD Maker and some new games including Chess
Chess
Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

, Mahjong
Mahjong
Mahjong, sometimes spelled Mah Jongg, is a game that originated in China, commonly played by four players...

, and Purble Place
Purble Place
Purble Place is a suite of computer games, developed by Oberon Games and included in Windows Vista and Windows 7 that offers an environment for children to practice pattern recognition, represented by the schoolhouse at the left of Purble Place. The object is to clear the tableau in the fewest...

), Internet Explorer 7
Internet Explorer 7
Windows Internet Explorer 7 is a web browser released by Microsoft in October 2006. Internet Explorer 7 is part of a long line of versions of Internet Explorer and was the first major update to the browser in more than 5 years...

, Windows Media Player 11, and a large number of underlying architectural changes. Windows Vista has the version number NT 6.0.

Windows Vista ships in six editions
Windows Vista editions
Windows Vista is available in six different marketing editions. With the exception of Windows Vista Starter, all editions support both 32-bit and 64-bit processor architectures....

:
  • Starter (only available in developing countries)
  • Home Basic
  • Home Premium
  • Business
  • Enterprise (only available to large businesses and enterprises)
  • Ultimate (combines both Home Premium and Enterprise)


All editions (except Starter edition) are currently available in both 32-bit and 64-bit versions. The biggest advantage of the 64-bit version is breaking the 4 gigabyte memory barrier, which 32-bit computers cannot fully access.

Windows Server 2008

Windows Server 2008, released on 27 February 2008, was originally known as Windows Server Codename "Longhorn". Windows Server 2008 builds on the technological and security advances first introduced with Windows Vista, and is significantly more modular than its predecessor, Windows Server 2003.

Windows Server 2008 ships in ten editions:
  • Windows Server 2008 Standard Edition (32-bit and 64-bit)
  • Windows Server 2008 Enterprise Edition (32-bit and 64-bit)
  • Windows Server 2008 Datacenter Edition (32-bit and 64-bit)
  • Windows HPC Server 2008
  • Windows Web Server 2008 (32-bit and 64-bit)
  • Windows Storage Server 2008 (32-bit and 64-bit)
  • Windows Small Business Server 2008 (64-bit only)
  • Windows Essential Business Server 2008 (32-bit and 64-bit)
  • Windows Server 2008 for Itanium-based Systems
  • Windows Server 2008 Foundation Server

Windows 7 and Windows Server 2008 R2

Windows 7 is the current major release after Windows Vista and was released to manufacturing on 22 July 2009, and reached general retail availability on 22 October 2009. It was previously known by the codenames Blackcomb and Vienna. Windows 7 has the version number NT 6.1.

Some features of Windows 7 are faster booting
Booting
In computing, booting is a process that begins when a user turns on a computer system and prepares the computer to perform its normal operations. On modern computers, this typically involves loading and starting an operating system. The boot sequence is the initial set of operations that the...

, Device Stage, Windows PowerShell
Windows PowerShell
Windows PowerShell is Microsoft's task automation framework, consisting of a command-line shell and associated scripting language built on top of, and integrated with the .NET Framework...

, less obtrusive User Account Control, multi-touch, and improved window management. Features included with Windows Vista and not in Windows 7 include the sidebar (although gadgets remain) and several programs that were removed in favor of downloading their Windows Live
Windows Live
Windows Live is the collective brand name for a set of services and software products from Microsoft, part of their software plus services platform. A majority of these services are Web applications, accessible from a browser, but there are also client-side binary applications that require...

 counterparts.

Windows 7 ships in six editions
Windows 7 editions
Windows 7 is available in six different editions, but only Home Premium, Professional, and Ultimate are widely available at retail. The other editions focus on other markets, such as the developing world or enterprise use. All editions support IA-32 CPUs and all editions except Starter support the...

:
  • Starter (available worldwide with new PCs only)
  • Home Basic
  • Home Premium
  • Professional
  • Enterprise (available to volume-license business customers only)
  • Ultimate (available to retail market with limited availability to OEMs)


In some countries (Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, United Kingdom, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, and Switzerland), there are other editions that lack some features such as Windows Media Player, Windows Media Center and Internet Explorer called names such as "Windows 7 N."
Microsoft focuses on selling Windows 7 Home Premium and Professional. All editions, except the Starter edition, are available in both 32-bit and 64-bit versions.
Unlike the corresponding Vista editions, the Professional and Enterprise editions are supersets of the Home Premium edition.

At the Professional Developers Conference
Professional Developers Conference
Microsoft's Professional Developers Conference is a conference for software developers, normally Windows developers.It covers new and upcoming technology from Microsoft, and so only occurs in the years when there is something new to talk about...

 (PDC) 2008, Microsoft also announced Windows Server 2008 R2
Windows Server 2008 R2
Windows Server 2008 R2 is a server operating system produced by Microsoft. It was released to manufacturing on July 22, 2009 and launched on October 22, 2009. According to the Windows Server Team blog, the retail availability was September 14, 2009. It is built on Windows NT 6.1, the same core...

, as the server variant of Windows 7. Windows Server 2008 R2 ships in 64-bit versions (x64
X86-64
x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...

 and Itanium
Itanium
Itanium is a family of 64-bit Intel microprocessors that implement the Intel Itanium architecture . Intel markets the processors for enterprise servers and high-performance computing systems...

) only.

Windows Home Server 2011

Windows Home Server 2011 code named 'Vail' was released on 6 April 2011. Windows Home Server 2011 is built on the Windows Server 2008 R2
Windows Server 2008 R2
Windows Server 2008 R2 is a server operating system produced by Microsoft. It was released to manufacturing on July 22, 2009 and launched on October 22, 2009. According to the Windows Server Team blog, the retail availability was September 14, 2009. It is built on Windows NT 6.1, the same core...

 code base It follows the release of Windows Home Server Power Pack 3 which added support for Windows 7 to Windows Home Server. Windows Home Server 2011 is considered a "major release". Windows Home Server 2011 is built on the Windows Server 2008 R2
Windows Server 2008 R2
Windows Server 2008 R2 is a server operating system produced by Microsoft. It was released to manufacturing on July 22, 2009 and launched on October 22, 2009. According to the Windows Server Team blog, the retail availability was September 14, 2009. It is built on Windows NT 6.1, the same core...

 code base (its predecessor having been built on Windows Server 2003
Windows Server 2003
Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...

) and only supports x86-64
X86-64
x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...

 hardware.

Windows Thin PC

In 2011, Microsoft introduced Windows Thin PC or WinTPC, which is a feature- and size-reduced locked-down version of Windows 7 expressly designed to turn older PCs into thin clients. WinTPC is available for software assurance
Microsoft Software Assurance
Microsoft Software Assurance is a Microsoft maintenance program aimed at business users who use Microsoft Windows, Microsoft Office, and other server and desktop applications...

 customers and relies on cloud computing
Cloud computing
Cloud computing is the delivery of computing as a service rather than a product, whereby shared resources, software, and information are provided to computers and other devices as a utility over a network ....

 in a business network. Wireless operation is supported since WinTPC has full wireless stack integration, but wireless operation may not be as good as the operation on a wired connection.

Windows 8 and Windows Server 8

Windows 8 is the upcoming version of Microsoft Windows, expected to be released in 2012. It will be the last 32 bit OS from Microsoft for home users. It was first mentioned at the 2011 Consumer Electronics Show
Consumer Electronics Show
The International Consumer Electronics Show is a major technology-related trade show held each January in the Las Vegas Convention Center, Las Vegas, Nevada, United States. Not open to the public, the Consumer Electronics Association-sponsored show typically hosts previews of products and new...

 in Las Vegas, where Microsoft announced that it would include support for system-on-a-chip and mobile ARM processors
ARM architecture
ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...

. On 1 June 2011, Microsoft officially unveiled the operating system at Computex 2011. The redesigned user interface in this release was designed to accommodate a variety of devices and screen sizes, in a departure from the previous Windows focus on personal computers. On the Building Windows 8 blog, it was announced that a computer running Windows 8 can boot up much faster than Windows 7. New features also include USB 3.0
USB 3.0
USB 3.0 is the second major revision of the Universal Serial Bus standard for computer connectivity.USB 3.0 has transmission speeds of up to 5 Gbit/s, which is 10 times faster than USB 2.0 . USB 3.0 significantly reduces the time required for data transmission, reduces power consumption, and...

 support, the Windows App Store, the ability to run from USB drives with Windows To Go
Windows To Go
Windows To Go is a feature in Windows 8 that allows the entire system to run from USB mass storage devices such as flash drives and external hard drives....

, and others.

The first public preview of Windows Server 8 was also shown by Microsoft at the 2011 Microsoft Worldwide Partner Conference.

Original line

  • Windows 1.0
    Windows 1.0
    Windows 1.0 is a 16-bit graphical operating environment, developed by Microsoft and released on 20 November 1985. It was Microsoft's first attempt to implement a multi-tasking graphical user interface-based operating environment on the PC platform. Windows 1.0 was the first version of Windows...

  • Windows 2.0
    Windows 2.0
    Windows 2.0 is a 16-bit Microsoft Windows GUI-based operating environment that was released on December 9, 1987 and is the successor to Windows 1.0. With Windows 2.1x in 1988, Windows 2.0 was supplemented by Windows/286 and Windows/386...

  • Windows 2.1 (Windows/286 and Windows/386)
  • Windows 3.0
    Windows 3.0
    Windows 3.0, a graphical environment, is the third major release of Microsoft Windows, and was released on 22 May 1990. It became the first widely successful version of Windows and a rival to Apple Macintosh and the Commodore Amiga on the GUI front...

  • Windows 3.1 (with a respective Windows for Workgroups release)
  • Windows 3.11 (also with a respective Windows for Workgroups release)
  • Windows 3.2 (a minor update to 3.1 for Simplified Chinese support)

Windows 9x

  • Windows 95
    Windows 95
    Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...

     (version 4.0)
  • Windows 98
    Windows 98
    Windows 98 is a graphical operating system by Microsoft. It is the second major release in the Windows 9x line of operating systems. It was released to manufacturing on 15 May 1998 and to retail on 25 June 1998. Windows 98 is the successor to Windows 95. Like its predecessor, it is a hybrid...

     and Windows 98 SE (version 4.1)
  • Windows Me
    Windows Me
    Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....

     (version 4.9)

Windows NT

  • Windows NT 3.1
    Windows NT 3.1
    Windows NT 3.1 is the first release of Microsoft's Windows NT line of server and business desktop operating systems, and was released to manufacturing on 27 July 1993. The version number was chosen to match the one of Windows 3.1, the then-latest operating environment from Microsoft, on account of...

  • Windows NT 3.5
    Windows NT 3.5
    Windows NT 3.5 is the second release of the Microsoft Windows NT operating system. It was released on 21 September 1994.One of the primary goals during Windows NT 3.5's development was to increase the speed of the operating system; as a result, the project was given the codename "Daytona" in...

  • Windows NT 3.51
    Windows NT 3.51
    Windows NT 3.51 is the third release of Microsoft's Windows NT line of operating systems. It was released on 30 May 1995, nine months after Windows NT 3.5. The release provided two notable feature improvements; firstly NT 3.51 was the first of a short-lived outing of Microsoft Windows on the...

  • Windows NT 4.0
    Windows NT 4.0
    Windows NT 4.0 is a preemptive, graphical and business-oriented operating system designed to work with either uniprocessor or symmetric multi-processor computers. It was the next release of Microsoft's Windows NT line of operating systems and was released to manufacturing on 31 July 1996...

  • Windows 2000
    Windows 2000
    Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...

     (NT version 5.0)
  • Windows XP
    Windows XP
    Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...

     and Windows Fundamentals for Legacy PCs
    Windows Fundamentals for Legacy PCs
    Windows Fundamentals for Legacy PCs is a thin client operating system from Microsoft, based on Windows XP Embedded, but optimized for older, less powerful hardware. It was released on 8 July 2006...

     (NT version 5.1)
  • Windows Server 2003
    Windows Server 2003
    Windows Server 2003 is a server operating system produced by Microsoft, introduced on 24 April 2003. An updated version, Windows Server 2003 R2, was released to manufacturing on 6 December 2005...

     and Windows XP Professional x64 Edition
    Windows XP Professional x64 Edition
    Microsoft Windows XP Professional x64 Edition released on April 25, 2005 is an edition of Windows XP for x86-64 personal computers. It is designed to use the expanded 64-bit memory address space provided by the x86-64 architecture....

     (NT version 5.2)
  • Windows Vista
    Windows Vista
    Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...

     and Windows Server 2008 (NT version 6.0)
  • Windows 7 and Windows Server 2008 R2
    Windows Server 2008 R2
    Windows Server 2008 R2 is a server operating system produced by Microsoft. It was released to manufacturing on July 22, 2009 and launched on October 22, 2009. According to the Windows Server Team blog, the retail availability was September 14, 2009. It is built on Windows NT 6.1, the same core...

     (NT version 6.1)
  • Windows 8
    Windows 8
    Windows 8 is the codename for the next version of the Microsoft Windows computer operating system following Windows 7. It has many changes from previous versions. In particular it adds support for ARM microprocessors in addition to the previously supported x86 microprocessors from Intel and AMD...

     and Windows Server 8 (NT version 6.2)

See also

  • Comparison of operating systems
    Comparison of operating systems
    These tables compare general and technical information for a number of widely used and currently available operating systems.Because of the large number and variety of available Linux distributions, they are all grouped under a single entry; see comparison of Linux distributions for a detailed...

  • History of operating systems
    History of operating systems
    The history of computer operating systems recapitulates to a degree the recent history of computer hardware.Operating systems provide a set of functions needed and used by most application programs on a computer, and the linkages needed to control and synchronize computer hardware...

  • Microsoft codenames
  • Microsoft version numbering

Further reading

  1. The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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