History of Microsoft Windows

In 1983, Microsoft announced the development of Windows, a graphical user interface (GUI) for its own operating system (MS-DOS), which had shipped for IBM PC and compatible computers since 1981. The product line has changed from a GUI product to a modern operating system over two families of design, each with its own codebase and default file system.

The 3.x and 4.x family includes Windows 3.0, Windows 3.1x, Windows 95, Windows 98, and Windows Me. Windows for Workgroups 3.11 added 32-bit networking and 32-bit disk access. Windows 95 added additional 32-bit capabilities (however, MS-DOS, some of the kernel, and supplementary utilities such as Disk Defragment remained 16-bit) and implemented a new object oriented user interface, elements of which are still used today.

The Windows NT family started with Windows NT 3.1 in 1993. Modern Windows operating system versions are based on the newer Windows NT kernel that was originally intended for OS/2. Windows runs on IA-32, x86-64, and Itanium processors. Microsoft is also working to bring Windows NT onto ARM in the next release of Windows. Earlier versions also ran on the i860, Alpha, MIPS, Fairchild Clipper, and PowerPC architectures. Some work was done to port it to the SPARC architecture.

With Windows NT 4.0 in 1996, the shell changed from Program Manager to Windows 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 customers.

Windows 1.0 was not a complete operating system, but rather an "operating environment" that extended MS-DOS, 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, a simple word processor; an appointment "calendar"; a "cardfiler"; a "notepad"; a "clock"; a "control panel"; a "computer terminal"; "Clipboard"; and RAM driver. It also included the MS-DOS Executive and a game called Reversi.

Microsoft had worked with Apple Computer to develop Desk Accessories and other minor pieces of software that were included with early Macintosh 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 came by way of its inclusion as a "run-time version" with Microsoft's new graphical applications, Excel and Word for Windows. 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 PageMaker appeared in a Windows version, having previously run only on Macintosh.

Versions 2.0x used the real-mode memory model, which confined it to a maximum of 1 megabyte of memory. In such a configuration, it could run under another multitasker like DESQview, which used the 286 protected mode.

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, the predecessor to XMS which would finally change the topology of IBM 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 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 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 May 1990. In addition to improved capabilities given to native applications, Windows also allowed users to better multitask older MS-DOS based software compared to Windows/386, thanks to the introduction of virtual memory.

Windows 3.0's user interface was finally a serious competitor to the user interface of the Macintosh 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 could run in real, standard, or 386 enhanced modes, and was compatible with any Intel processor from the 8086/8088 up to the 80286 and 80386. 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, 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.

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 had cooperatively been developing OS/2 as a successor to DOS. OS/2 would take full advantage of the aforementioned protected mode of the Intel 80286 processor and up to 16 MB of memory. OS/2 1.0, released in 1987, supported swapping and multitasking and allowed running of DOS executables.

A GUI, called the Presentation Manager (PM), was not available with OS/2 until version 1.1, released in 1988. Its API 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, HPFS, to replace the FAT 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. 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. 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 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. The Windows API became the de-facto standard for consumer software.

Meanwhile, Microsoft continued to develop Windows NT. The main architect of the system was Dave Cutler, one of the chief architects of VMS at Digital Equipment Corporation (later acquired by Compaq, now part of Hewlett-Packard). 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 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 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 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, codenamed Chicago), which would unify the two into one operating system. This successor was codenamed Cairo. 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—albeit Windows 2000, 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 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.

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 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, 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. 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 (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, 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 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". A new object oriented 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) 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 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 process, Windows 95 applications ran solely in 386 enhanced mode, with a flat 32-bit address space and virtual memory. These features make it possible for Win32 applications to address up to 2 gigabytes 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, although Windows 95/98/ME did not support more than 512 megabytes of physical RAM without obscure system tweaks.

IBM 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 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 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 into the installation.
 * Windows 95 B - (OSR2) included several major enhancements, Internet Explorer (IE) 3.0 and full FAT32 file system support.
 * Windows 95 B USB - (OSR2.1) included basic USB 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 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! add-on pack was sold for Windows 95.

Windows NT 4.0
Windows NT 4.0 was the successor of 3.51 (1995) and 3.5 (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 and MSRPC. 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 and clustering)
 * Windows NT 4.0 Terminal Server

Windows 98
On 25 June 1998, Microsoft released Windows 98 (codenamed Memphis). It included new hardware drivers and the FAT32 file system which supports disk partitions that are larger than 2 GB (first introduced in Windows 95 OSR2). USB support in Windows 98 is marketed as a vast improvement over Windows 95. The release continued the controversial inclusion of the Internet Explorer browser with the operating system that started with Windows 95 OEM Service Release 1. The action eventually led to the filing of the United States v. Microsoft case, dealing with the question of whether Microsoft was introducing unfair practices into the market in an effort to eliminate competition from other companies such as Netscape.

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, a form of network address translation, allowing several machines on a LAN (Local Area Network) to share a single Internet connection. Hardware support through device drivers was increased. Many minor problems that existed in the first edition were fixed making it, according to many, the most stable release of the Windows 9x family.

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, a near-complete replacement of the NT 4.0 Windows Server domain model, which built on industry-standard technologies like DNS, LDAP, and Kerberos to connect machines to one another. Terminal Services, 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, and a revised DirectX 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.

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 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 as updates for older Windows versions (System Restore and Windows Movie Maker were exceptions). Windows Me was criticized for stability issues, and for lacking real mode 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) kernel and MS-DOS.

Windows XP


On 25 August 2001, Microsoft released Windows XP (codenamed "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, leading to the release of three major Service Packs. 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 25 October 2001 to 30 January 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 laptops - lacked features such as joining Active Directory Domain, Remote Desktop Server and Internet Information Services Server.
 * Windows XP Home Edition N, as above, but without a default installation of Windows Media Player, as mandated by a European Union 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 (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
 * 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, released on 25 April 2005 for home and workstation systems utilizing 64-bit processors based on the x86-64 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 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 features, a new "Manage Your Server" 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" 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 1) plus an add-on package. Among the new features 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 for x86-64 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 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 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 (WinFLP). It is only available to Software Assurance 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, designed for consumer use. The system was announced on 7 January 2007 by Bill Gates. 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 was released on 8 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, 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 GUI, new applications (such as Windows Calendar, Windows DVD Maker and some new games including Chess, Mahjong, and Purble Place), Internet Explorer 7, 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:
 * Starter (only available in developing countries)
 * Home Basic
 * Home Premium
 * Business
 * Enterprise (only available to large business and enterprise)
 * 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, Device Stage, Windows PowerShell, 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 counterparts.

Windows 7 ships in six editions:
 * Starter (available worldwide)
 * 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 (PDC) 2008, Microsoft also announced Windows Server 2008 R2, as the server variant of Windows 7. Windows Server 2008 R2 ships in 64-bit versions (x64 and Itanium) 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 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". (its predecessor having been built on Windows Server 2003) and only supports x86-64 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 customers and relies on cloud computing 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 2012


Windows 8 is the upcoming version of Microsoft Windows. Windows RT, a special version of Windows 8, runs on system-on-a-chip devices with mobile ARM processors. Windows 8 features a redesigned user interface, designed to make it easier for touchscreen users to use Windows. The interface includes a full-screen Start screen to replace the Start menu, and a new full-screen application platform. The desktop interface is also present for running windowed applications, although Windows RT will not run any desktop applications not included in the system. 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 support, the Windows Store, the ability to run from USB drives with Windows To Go, and others.

Windows 8 will ship with three editions and one edition called Windows RT will only be pre-installed on ARM tablets. The first public preview of Windows Server 2012 was also shown by Microsoft at the 2011 Microsoft Worldwide Partner Conference.
 * Windows 8
 * Windows 8 Pro
 * Windows RT (Only installed on ARM tablets)
 * Windows 8 Enterprise

Windows 8 Release Preview and Windows Server 2012 Release Candidate were both released on May 31, 2012.

Windows 8 and Windows Server 2012 was released to manufacturing on 1 August 2012. Microsoft has said that Windows Server 2012 will be available on 4 September 2012 and Windows 8 will be available on 26 October 2012.

Original line

 * Windows 1.0
 * Windows 2.0
 * Windows 2.1 (Windows/286 and Windows/386)
 * Windows 3.0
 * 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 (version 4.0)
 * Windows 98 and Windows 98 SE (version 4.1)
 * Windows Me (version 4.9)

Windows NT

 * Windows NT 3.1
 * Windows NT 3.5
 * Windows NT 3.51
 * Windows NT 4.0
 * Windows 2000 (NT version 5.0)
 * Windows XP and Windows Fundamentals for Legacy PCs (NT version 5.1)
 * Windows Server 2003 and Windows XP Professional x64 Edition (NT version 5.2)
 * Windows Vista and Windows Server 2008 (NT version 6.0)
 * Windows 7 and Windows Server 2008 R2 (NT version 6.1)
 * Windows 8 and Windows Server 2012 (NT version 6.2)
 * Windows 8.1
 * Windows 10
 * Windows 10X (cancelled)
 * Windows 11