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Microsoft Windows

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Microsoft Windows
Windows logo
Windows logo introduced in 2012
Windows 8 Start Screen.png
Windows 8, showing the start screen
Company / developer Microsoft
Programmed in C, C++ and Assembly language
OS family Windows 9x, Windows CE and Windows NT
Working state Publicly released
Source model Closed source / Shared source
Initial release November 20, 1985 (1985-11-20) (as Windows 1.0)
Latest stable release

Windows 8
NT 6.2 (Build 9200) (October 26, 2012 (2012-10-26)) [±]

Windows Server 2012
NT 6.2 (Build 9200) (September 4, 2012 (2012-09-04)) [±]
Latest unstable release NT 6.3 (Build 9364)
Marketing target Personal computing
Available language(s) 137 languages ( listing of available Windows 7 language packs)
Update method Windows Update, Windows Anytime Upgrade
Supported platforms ARM, IA-32, x86-64 and Itanium
Kernel type Hybrid (Windows NT family), DOS (16-bit Windows and Windows 9x/ME series)
Default user interface Graphical ( Windows Shell)
License Proprietary commercial software
Official website

Microsoft Windows is a series of graphical interface operating systems developed, marketed, and sold by Microsoft.

Microsoft introduced an operating environment named Windows on November 20, 1985 as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces (GUI). Microsoft Windows came to dominate the world's personal computer market with over 90% market share, overtaking Mac OS, which had been introduced in 1984.

As of April 2013, the most recent versions of Windows for personal computers, mobile devices, server computers and embedded devices are respectively Windows 8, Windows Phone 8, Windows Server 2012 and Windows Embedded 8 Industry.

Version history

The term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are generally categorized as follows:

The classic Windows logo, used from 1992 until the release of Windows XP in 2001

Early versions

The history of Windows dates back to September 1981, when Chase Bishop, a computer scientist, designed the first model of an electronic device and project "Interface Manager" was started. It was announced in November 1983 (after the Apple Lisa, but before the Macintosh) under the name "Windows", but Windows 1.0 was not released until November 1985. Windows 1.0 achieved little popularity and was to compete with Apple's own operating system. Windows 1.0 is not a complete operating system; rather, it extends MS-DOS. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Included components include Calculator, Calendar, Cardfile, Clipboard viewer, Clock, Control Panel, Notepad, Paint, Reversi, Terminal and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only modal dialog boxes may appear over other windows.

Windows 2.0 was released in December 1987 and was more popular than its predecessor. It features several improvements to the user interface and memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights. Windows 2.0 also introduced more sophisticated keyboard shortcuts and could make use of expanded memory.

Windows 2.1 was released in two different versions: Windows/286 and Windows/386. Windows/386 employs the virtual 8086 mode of Intel 80386 to multitask several DOS programs and the paged memory model to emulate expanded memory using available extended memory. Windows/286, in spite of its name, runs on both Intel 8086 and Intel 80286. It runs in real mode but can make use of the high memory area.

In addition to full Windows-packages, there were runtime-only versions that shipped with early Windows software from third parties and made it possible to run their Windows software on MS-DOS and without the full Windows feature set.

The early versions of Windows are often thought of as graphical shells, mostly because they ran on top of MS-DOS and use it for file system services. However, even the earliest Windows versions already assumed many typical operating system functions; notably, having their own executable file format and providing their own device drivers (timer, graphics, printer, mouse, keyboard and sound). Unlike MS-DOS, Windows allowed users to execute multiple graphical applications at the same time, through cooperative multitasking. Windows implemented an elaborate, segment-based, software virtual memory scheme, which allows it to run applications larger than available memory: code segments and resources are swapped in and thrown away when memory became scarce; data segments moved in memory when a given application had relinquished processor control.

Windows 3.0 and 3.1

Windows 3.0, released in 1990, improved the design, mostly because of virtual memory and loadable virtual device drivers ( VxDs) that allow Windows to share arbitrary devices between multi-tasked DOS applications. Windows 3.0 applications can run in protected mode, which gives them access to several megabytes of memory without the obligation to participate in the software virtual memory scheme. They run inside the same address space, where the segmented memory provides a degree of protection. Windows 3.0 also featured improvements to the user interface. Microsoft rewrote critical operations from C into assembly. Windows 3.0 is the first Microsoft Windows version to achieve broad commercial success, selling 2 million copies in the first six months.

Windows 3.1, made generally available on March 1, 1992, featured a facelift. In August 1993, Windows for Workgroups, a special version with integrated peer-to-peer networking features and a version number of 3.11, was released. It was sold along Windows 3.1. Support for Windows 3.1 ended on December 31, 2001.

Windows 9x

Windows 95 was released on August 24, 1995, featuring a new object oriented user interface, support for long file names of up to 255 characters, the ability to automatically detect and configure installed hardware ( plug and play) and preemptive multitasking. Windows 95 was designed to replace Windows 3.1, Windows for Workgroups and MS-DOS and was marketed in consumers sector. It can run native 32-bit applications, and features increased stability over its predecessor.

Microsoft published four OEM Service Releases (OSR) of Windows 95, each of which was roughly equivalent to a service pack. Mainstream support for Windows 95 ended on December 31, 2000 and extended support for Windows 95 ended on December 31, 2001.

Next in the consumer line is Microsoft Windows 98, released on June 25, 1998. It was followed with the release of Windows 98 Second Edition (often shortened to Windows 98 SE) in May 1999. Windows 98 added support for Windows Driver Model, USB composite devices, ACPI, hibernation and multi-monitor computers. Windows 98 SE added Internet Explorer 5.0 and Windows Media Player 6.2 amongst other upgrades. Mainstream support for Windows 98 ended on June 30, 2002 and extended support for Windows 98 ended on July 11, 2006.

In September 2000, Windows ME (Millennium Edition) was released as successor to Windows 98. Windows ME was developed based on the same core as Windows 98, but it adopted some aspects of Windows 2000 (part of the Windows NT family) and removed the "boot in DOS mode" option. New features include Universal Plug and Play, and System Restore, which allows users to revert their computers' settings back to an earlier date. Windows ME was heavily criticized for slowness, freezes and hardware problems. PC World called Windows ME one of the worst operating systems Microsoft ever released.

Windows NT family

The Windows logo (2001–2006), introduced in Windows XP
The Windows logo (2006–2012), introduced in Windows Vista
The Windows logo used as of October 2012, introduced in Windows Server 2012

In July 1993, Microsoft released Windows NT based on a new kernel. The NT family of Windows systems was fashioned and marketed for higher reliability business use, considered to be the professional OS. The first release was Windows NT 3.1 (1993), numbered "3.1" to match the consumer Windows version, which was followed by Windows NT 3.5 (1994), Windows NT 3.51 (1995), Windows NT 4.0 (1996) and Windows 2000 (2000). Windows NT was the first Windows version to utilize preemptive multitasking. Windows NT 4.0 was the first in this line to implement the "Windows 95" user interface (and the first to include Windows 95's built-in 32-bit runtimes).

In February 2000, Microsoft released Windows 2000 as successor to Windows NT 4.0. During 2004, part of the source code for Windows 2000 was leaked onto the Internet. Windows 2000 is the last NT-based Windows release that does not include Microsoft Product Activation. After Windows 2000, the Windows NT family was split into two lines: A client line, including Windows XP and its successors, consists of operating systems produced for installation on client computers, such as workstations, home computers, laptops, tablet computers and media centers. A Windows Server line, including Windows Server 2003 and it successors, consists of operating systems produced for server computers. Later, a third line for embedded systems was added with the introduction of Windows Embedded.

Windows XP, Vista and 7

Microsoft moved to combine their consumer and business operating systems with Windows XP that was released on October 25, 2001. Windows XP is built on the Windows NT kernel, retooled to also function as a home operating system. This new version was widely praised in computer magazines.

XP shipped in two distinct editions, "Home" and "Professional", the former lacking many of the superior security and networking features of the Professional edition. Additionally, the first "Media Centre" edition was released in 2002, with an emphasis on support for DVD and TV functionality including program recording and a remote control. A niche market versions for tablet PCs was also released. Mainstream support for Windows XP ended on April 14, 2009. Extended support will continue until April 8, 2014.

After Windows 2000, Microsoft diverged release schedules for server operating systems. In April 2003, Windows Server 2003 was introduced, replacing the Windows 2000 line of server products with a number of new features and a strong focus on security. It was followed in December 2005 by Windows Server 2003 R2.

After a lengthy development process, Windows Vista was released on November 30, 2006 for volume licensing and January 30, 2007 for consumers. It contains a number of new features, from a redesigned shell and user interface to significant technical changes, with a particular focus on security features. It is available in a number of different editions, and has been subject to some criticism. Vista's server counterpart, Windows Server 2008 was released in early 2008.

On July 22, 2009, Windows 7 and Windows Server 2008 R2 were released as RTM (release to manufacturing) while the former was released to the public 3 months later on October 22, 2009. Unlike its predecessor, Windows Vista, which introduced a large number of new features, Windows 7 was intended to be a more focused, incremental upgrade to the Windows line, with the goal of being compatible with applications and hardware with which Windows Vista was already compatible. Windows 7 has multi-touch support, a redesigned Windows shell with a new taskbar, referred to as the Superbar, a home networking system called HomeGroup, and performance improvements.

Windows 8

Windows 8, the successor to Windows 7, was released to manufacturing on 1 August 2012 and was made generally available on 26 October 2012. Windows 8 uses a redesigned user interface based on Metro design language, to improve usability on touch-based devices (such as tablets) and better compete with the Apple iPad and Android. The core of this user interface is the Start screen, the third version the Start menu since Windows 95. Applications on the Start screen are represented by tiles that are big enough to be selected by a human finger and display dynamic information, depending on the application in charge of them. Applications designed based on Windows 8 model either run full-screen or in a sidebar to the left or right of the screen. The new applications are primarily available through Windows Store. One edition of Windows 8, named Windows RT, is the first version of Windows for ARM-based devices. Windows RT supports only Windows Store apps.

The desktop is available as an application to help interface with the traditional windowed applications. For the first time since Windows 95, the Start button, which mainly served as a way of invoking the Start menu with a mouse, is no longer available on the taskbar. The Start screen is now invoked by clicking the bottom-left corner of the screen, or by clicking the Start button in the charms. Taskbar itself is only accessible when the desktop application is on the top; the charms, however, is almost always accessible. The keyboard shortcut for invoking the Start menu, the Windows key, still functions as before.

Third-party shell extensions offer a new Start button on taskbar, a new Start menu, or an entirely different Windows Shell altogether. (See List of Start Menu replacements for Windows 8.)

An update to Windows 8, codenamed Windows Blue, is in development, and scheduled for release in 2013. Leaked alpha versions of Windows Blue have hit the Internet.

Multilingual support: IMEs and LIPs

There are three main issues involved in making English-language Windows multilingual: (1) some languages require an Input Method Editor (IME) to enter text, (2) many users will want application menus (such as MS Office menus) to display in their own language, and they may also want to use a keyboard that matches the normal keyboard layout and marking for their own language, and (3) some users will want Windows menus and messages to display in their own language, i.e. they will want to switch from an English Windows environment to another language.

For languages like Italian, Spanish, French and German, (2) alone may suffice. For languages like Chinese, Japanese, and Korean ( CJK), an IME (1) is also required. This is bundled with the corresponding language version of Windows, but is also available as a separate download for English Windows, as described below; (1) and (2) can be essentially free (apart from the custom keyboard). For some languages, (3), multilingual support for Windows, is a free download for Windows XP and later—but it requires Windows 7 Ultimate or better for languages such as Chinese, Japanese, and Korean.

(1) After releasing Chinese, Japanese, and Korean bundles of Office 2010 and IME 2010, Microsoft made IME 2010 available as a free upgrade for users of the earlier IME versions of Windows. Microsoft later made these Chinese, Japanese, and Korean IME versions available free to users of Windows XP and later, including English Windows XP (but now says that users should own some version of MS Office). Each IME package enables the entering of text in the corresponding language; necessary fonts may be bundled with it (or supplementary fonts offered with the corresponding version of Office).

(2) Microsoft now also offers Language Interface Packs (LIPs) for MS Office. Some LIPs are free; some "Language Packs" (such as the CJK ones) are sold separately and may include spelling and grammar checking tools. (Recent application software from some companies may support two or more popular languages).

(3) Microsoft now also offers Language Interface Packs (LIPs) that allow users to view Windows menus, dialog boxes, and other user interface items in their preferred language. These are free; most are for English Windows (XP and later)—however, Chinese, Japanese, and Korean LIP downloads require Windows 7 Ultimate or Enterprise. These LIPs include IMEs where applicable.

Platform support

Windows NT included support for several different platforms before the x86-based personal computer became dominant in the professional world. Windows NT 4.0 and its predecessors supported PowerPC, DEC Alpha and MIPS R4000. (Although some these platforms implement 64-bit computing, the operating system treated them as 32-bit.) However, Windows 2000, the successor of Windows NT 4.0, dropped support for all platforms except the third generation x86 (known as IA-32) or newer in 32-bit mode. The client line of Window NT family still runs on IA-32, although the Windows Server line has ceased supporting this platform with the release of Windows Server 2008 R2.

With the introduction of the Intel Itanium architecture (IA-64), Microsoft released new versions of Windows to support it. Itanium versions of Windows XP and Windows Server 2003 were released at the same time as their mainstream x86 counterparts. Windows XP 64-Bit Edition, released in 2005, is the last Windows client operating systems to support Itanium. Windows Server line continued to support this platform until Windows Server 2012; Windows Server 2008 R2 is the last Windows operating system to support Itanium architecture.

On April 25, 2005, Microsoft released Windows XP Professional x64 Edition and Windows Server 2003 x64 Editions to support the x86-64 (or simply x64), the eighth generation of x86 architecture. Windows Vista was the first client version of Windows NT to be released simultaneously in IA-32 and x64 editions. x64 is still supported.

An edition of Windows 8 known as Windows RT was specifically created for computers with ARM architecture.

Windows CE

Windows CE (officially known as Windows Embedded Compact), is an edition of Windows that runs on minimalistic computers, like satellite navigation systems and some mobile phones. Windows Embedded Compact is based on its own dedicated kernel, dubbed Windows CE kernel. Microsoft licenses Windows CE to OEMs and device makers. The OEMs and device makers can modify and create their own user interfaces and experiences, while Windows CE provides the technical foundation to do so.

Windows CE was used in the Dreamcast along with Sega's own proprietary OS for the console. Windows CE was the core from which Windows Mobile was derived. Its successor, Windows Phone 7, was based on components from both Windows CE 6.0 R3 and Windows CE 7.0. Windows Phone 8 however, is based on the same NT-kernel as Windows 8.

Windows Embedded Compact is not to be confused with Windows XP Embedded or Windows NT 4.0 Embedded, modular editions of Windows based on Windows NT kernel.

Timeline of releases

The Windows family tree

Usage share

Source Net Market Share Global Stats W3Counter
Date March 2013 March 2013 March 2013
All versions 91.88% 86.02% 73.18%
Windows 7 44.73% 52.61% 43.09%
Windows XP 38.73% 23.38% 21.67%
Windows Vista 4.99% 6.13% 5.01%
Windows 8 3.31% 3.9% 3.41%
Windows NT 0.07%
Windows 2000 0.05%


Consumer versions of Windows were originally designed for ease-of-use on a single-user PC without a network connection, and did not have security features built in from the outset. However, Windows NT and its successors are designed for security (including on a network) and multi-user PCs, but were not initially designed with Internet security in mind as much, since, when it was first developed in the early 1990s, Internet use was less prevalent.

These design issues combined with programming errors (e.g. buffer overflows) and the popularity of Windows means that it is a frequent target of computer worm and virus writers. In June 2005, Bruce Schneier's Counterpane Internet Security reported that it had seen over 1,000 new viruses and worms in the previous six months. In 2005, Kaspersky Lab found around 11,000 malicious programs—viruses, Trojans, back-doors, and exploits written for Windows.

Microsoft releases security patches through its Windows Update service approximately once a month (usually the second Tuesday of the month), although critical updates are made available at shorter intervals when necessary. In versions of Windows after and including Windows 2000 SP3 and Windows XP, updates can be automatically downloaded and installed if the user selects to do so. As a result, Service Pack 2 for Windows XP, as well as Service Pack 1 for Windows Server 2003, were installed by users more quickly than it otherwise might have been.

While the Windows 9x series offered the option of having profiles for multiple users, they had no concept of access privileges, and did not allow concurrent access; and so were not true multi-user operating systems. In addition, they implemented only partial memory protection. They were accordingly widely criticised for lack of security.

The Windows NT series of operating systems, by contrast, are true multi-user, and implement absolute memory protection. However, a lot of the advantages of being a true multi-user operating system were nullified by the fact that, prior to Windows Vista, the first user account created during the setup process was an administrator account, which was also the default for new accounts. Though Windows XP did have limited accounts, the majority of home users did not change to an account type with fewer rights – partially due to the number of programs which unnecessarily required administrator rights – and so most home users ran as administrator all the time.

Windows Vista changes this by introducing a privilege elevation system called User Account Control. When logging in as a standard user, a logon session is created and a token containing only the most basic privileges is assigned. In this way, the new logon session is incapable of making changes that would affect the entire system. When logging in as a user in the Administrators group, two separate tokens are assigned. The first token contains all privileges typically awarded to an administrator, and the second is a restricted token similar to what a standard user would receive. User applications, including the Windows Shell, are then started with the restricted token, resulting in a reduced privilege environment even under an Administrator account. When an application requests higher privileges or "Run as administrator" is clicked, UAC will prompt for confirmation and, if consent is given (including administrator credentials if the account requesting the elevation is not a member of the administrators group), start the process using the unrestricted token.

File permissions

All Windows versions from Windows NT 3 have been based on a file system permission system referred to as AGLP (Accounts, Global, Local, Permissions) AGDLP which in essence where file permissions are applied to the file/folder in the form of a 'local group' which then has other 'global groups' as members. These global groups then hold other groups or users depending on different Windows versions used. This system varies from other vendor products such as Linux and NetWare due to the 'static' allocation of permission being applied directory to the file or folder. However using this process of AGLP/AGDLP/AGUDLP allows a small number of static permissions to be applied and allows for easy changes to the account groups without reapplying the file permissions on the files and folders.

Windows Defender

On January 6, 2005, Microsoft released a Beta version of Microsoft AntiSpyware, based upon the previously released Giant AntiSpyware. On February 14, 2006, Microsoft AntiSpyware became Windows Defender with the release of Beta 2. Windows Defender is a freeware program designed to protect against spyware and other unwanted software. Windows XP and Windows Server 2003 users who have genuine copies of Microsoft Windows can freely download the program from Microsoft's web site, and Windows Defender ships as part of Windows Vista and 7. In Windows 8, Windows Defender and Microsoft Security Essentials have been combined into a single program, named Windows Defender. It is based on Microsoft Security Essentials, borrowing its features and user interface. Although it is enabled by default, it can be turned off to use another anti-virus solution. Windows Malicious Software Removal Tool and the optional Microsoft Safety Scanner are two other free security products offered by Microsoft.

Third-party analysis

In an article based on a report by Symantec, has described Microsoft Windows as having the "fewest number of patches and the shortest average patch development time of the five operating systems it monitored in the last six months of 2006."

A study conducted by Kevin Mitnick and marketing communications firm Avantgarde in 2004 found that an unprotected and unpatched Windows XP system with Service Pack 1 lasted only 4 minutes on the Internet before it was compromised, and an unprotected and also unpatched Windows Server 2003 system was compromised after being connected to the internet for 8 hours. This study does not apply to Windows XP systems running the Service Pack 2 update (released in late 2004), which vastly improved the security of Windows XP. The computer that was running Windows XP Service Pack 2 was not compromised. The AOL National Cyber Security Alliance Online Safety Study of October 2004 determined that 80% of Windows users were infected by at least one spyware/ adware product. Much documentation is available describing how to increase the security of Microsoft Windows products. Typical suggestions include deploying Microsoft Windows behind a hardware or software firewall, running anti-virus and anti-spyware software, and installing patches as they become available through Windows Update.

Emulation software

Emulation allows the use of some Windows applications without using Microsoft Windows. These include:

  • Wine – a free and open-source implementation of the Windows API, allowing one to run many Windows applications on x86-based platforms, including UNIX, Linux and OS X. Wine developers refer to it as a "compatibility layer" and use Windows-style APIs to emulate Windows environment.
    • CrossOver – a Wine package with licensed fonts. Its developers are regular contributors to Wine, and focus on Wine running officially supported applications.
    • Cedega – proprietary fork of Wine by TransGaming Technologies, designed specifically for running Microsoft Windows games on Linux. A version of Cedega known as Cider allows Windows games to run on OS X. Since Wine was licensed under the LGPL, Cedega has been unable to port the improvements made to Wine to their proprietary codebase. Cedega ceased its service in February 2011.
    • Darwine – a port of Wine for OS X and Darwin. Operates by running Wine on QEMU.
  • ReactOS – an open-source OS intended to run the same software as Windows, originally designed to simulate Windows NT 4.0, now aiming at Windows 7 compatibility. It has been in the development stage since 1996.
  • Linspire – formerly LindowsOS, a commercial Linux distribution initially created with the goal of running major Windows software. Changed its name to Linspire after Microsoft v. Lindows. Discontinued in favour of Xandros Desktop.
  • Freedows OS – an open-source attempt at creating a Windows clone for x86 platforms, intended to be released under the GNU General Public License. Started in 1996 by Reece K. Sellin, the project was never completed, getting only to the stage of design discussions which featured a number of novel concepts until it was suspended in 2002.
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