Computer operating systems
"Windows" redirects here. For the part of a building, see Window . For other uses, see Windows (disambiguation)
Microsoft🫰 Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to🫰 a certain sector of the computing industry. For instance, Windows NT for consumer and corporate desktops, Windows Server for servers,🫰 and Windows IoT for embedded systems. Defunct Windows families include Windows 9x, Windows Mobile, Windows Phone, and Windows Embedded Compact.
The🫰 first version of Windows was released on November 20, 1985, as a graphical operating system shell for MS-DOS in response🫰 to the growing interest in graphical user interfaces (GUIs).[12]
Windows is the most popular desktop operating system in the world, with🫰 a 70% market share as of March 2024 , according to StatCounter.[13] However, Windows is not the most used operating🫰 system when including both mobile and desktop OSes, due to Android's massive growth.[14]
As of December 2024 , the most recent🫰 version of Windows is Windows 11 for consumer PCs and tablets, Windows 11 Enterprise for corporations, and Windows Server 2024🫰 for servers.
Genealogy
By marketing role
Microsoft, the developer of Windows, has registered several trademarks, each of which denotes a family of Windows🫰 operating systems that target a specific sector of the computing industry. As of 2014, the following Windows families were being🫰 actively developed:
These Windows families are no longer being developed:
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:
Early versions
The history of Windows dates back to 1981🫰 when Microsoft started work on a program called "Interface Manager". 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.[17] Windows 1.0 was🫰 to compete with Apple's operating system, but achieved little popularity. 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. Components included 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. Microsoft sold as included Windows Development libraries with🫰 the C development environment, which included numerous windows samples.[18]
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.[19] 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 (eventually settled in court in Microsoft's favor in 1993).[20][21] 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 uses the🫰 virtual 8086 mode of the 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 processors.🫰 It runs in real mode but can make use of the high memory area.[citation needed]
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 used it for file system services.[22] 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.x
Windows 3.0, released in 1990
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.[citation needed] 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 was the first version of Windows to achieve broad🫰 commercial success, selling 2 million copies in the first six months.[23][24]
Versions before Windows 95 had to be installed from floppy🫰 disks by end users (or in professional environments with a network installation); here Windows for Workgroups with nine 3.5-inch-disks to🫰 be inserted sequentially.
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🫰 with Windows 3.1. Support for Windows 3.1 ended on December 31, 2001.[25]
Windows 3.2, released in 1994, is an updated version🫰 of the Chinese version of Windows 3.1.[26] The update was limited to this language version, as it fixed only issues🫰 related to the complex writing system of the Chinese language.[27] Windows 3.2 was generally sold by computer manufacturers with a🫰 ten-disk version of MS-DOS that also had Simplified Chinese characters in basic output and some translated utilities.
Windows 9x
The next major🫰 consumer-oriented release of Windows, Windows 95, was released on August 24, 1995. While still remaining MS-DOS-based, Windows 95 introduced support🫰 for native 32-bit applications, plug and play hardware, preemptive multitasking, long file names of up to 255 characters, and provided🫰 increased stability over its predecessors. Windows 95 also introduced a redesigned, object oriented user interface, replacing the previous Program Manager🫰 with the Start menu, taskbar, and Windows Explorer shell. Windows 95 was a major commercial success for Microsoft; Ina Fried🫰 of CNET remarked that "by the time Windows 95 was finally ushered off the market in 2001, it had become🫰 a fixture on computer desktops around the world."[28] Microsoft published four OEM Service Releases (OSR) of Windows 95, each of🫰 which was roughly equivalent to a service pack. The first OSR of Windows 95 was also the first version of🫰 Windows to be bundled with Microsoft's web browser, Internet Explorer.[29] Mainstream support for Windows 95 ended on December 31, 2000,🫰 and extended support for Windows 95 ended on December 31, 2001.[30]
Windows 95 was followed up with the release of Windows🫰 98 on June 25, 1998, which introduced the Windows Driver Model, support for USB composite devices, support for ACPI, hibernation,🫰 and support for multi-monitor configurations. Windows 98 also included integration with Internet Explorer 4 through Active Desktop and other aspects🫰 of the Windows Desktop Update (a series of enhancements to the Explorer shell which was also made available for Windows🫰 95). In May 1999, Microsoft released Windows 98 Second Edition, an updated version of Windows 98. 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.[31]
On September 14, 2000, Microsoft released Windows Me (Millennium🫰 Edition), the last DOS-based version of Windows. Windows Me incorporated visual interface enhancements from its Windows NT-based counterpart Windows 2000,🫰 had faster boot times than previous versions (which however, required the removal of the ability to access a real mode🫰 DOS environment, removing compatibility with some older programs),[32] expanded multimedia functionality (including Windows Media Player 7, Windows Movie Maker, and🫰 the Windows Image Acquisition framework for retrieving
from scanners and digital cameras), additional system utilities such as System File🫰 Protection and System Restore, and updated home networking tools.[33] However, Windows Me was faced with criticism for its speed and🫰 instability, along with hardware compatibility issues and its removal of real mode DOS support. PC World considered Windows Me to🫰 be one of the worst operating systems Microsoft had ever released, and the fourth worst tech product of all time.[16]
Windows🫰 NT
Version history
Early versions (Windows NT 3.1/3.5/3.51/4.0/2000)
Windows logo, 1995
In November 1988, a new development team within Microsoft (which included former Digital🫰 Equipment Corporation developers Dave Cutler and Mark Lucovsky) began work on a revamped version of IBM and Microsoft's OS/2 operating🫰 system known as "NT OS/2". NT OS/2 was intended to be a secure, multi-user operating system with POSIX compatibility and🫰 a modular, portable kernel with preemptive multitasking and support for multiple processor architectures. However, following the successful release of Windows🫰 3.0, the NT development team decided to rework the project to use an extended 32-bit port of the Windows API🫰 known as Win32 instead of those of OS/2. Win32 maintained a similar structure to the Windows APIs (allowing existing Windows🫰 applications to easily be ported to the platform), but also supported the capabilities of the existing NT kernel. Following its🫰 approval by Microsoft's staff, development continued on what was now Windows NT, the first 32-bit version of Windows. However, IBM🫰 objected to the changes, and ultimately continued OS/2 development on its own.[34][35]
Windows NT was the first Windows operating system based🫰 on a hybrid kernel. The hybrid kernel was designed as a modified microkernel, influenced by the Mach microkernel developed by🫰 Richard Rashid at Carnegie Mellon University, but without meeting all of the criteria of a pure microkernel.
The first release of🫰 the resulting operating system, Windows NT 3.1 (named to associate it with Windows 3.1) was released in July 1993, with🫰 versions for desktop workstations and servers. Windows NT 3.5 was released in September 1994, focusing on performance improvements and support🫰 for Novell's NetWare, and was followed up by Windows NT 3.51 in May 1995, which included additional improvements and support🫰 for the PowerPC architecture. Windows NT 4.0 was released in June 1996, introducing the redesigned interface of Windows 95 to🫰 the NT series. On February 17, 2000, Microsoft released Windows 2000, a successor to NT 4.0. The Windows NT name🫰 was dropped at this point in order to put a greater focus on the Windows brand.[35]
Windows XP
The next major version🫰 of Windows NT, Windows XP, was released to manufacturing (RTM) on August 24, 2001, and to the general public on🫰 October 25, 2001. The introduction of Windows XP aimed to unify the consumer-oriented Windows 9x series with the architecture introduced🫰 by Windows NT, a change which Microsoft promised would provide better performance over its DOS-based predecessors. Windows XP would also🫰 introduce a redesigned user interface (including an updated Start menu and a "task-oriented" Windows Explorer), streamlined multimedia and networking features,🫰 Internet Explorer 6, integration with Microsoft's .NET Passport services, a "compatibility mode" to help provide backwards compatibility with software designed🫰 for previous versions of Windows, and Remote Assistance functionality.[36][37]
At retail, Windows XP was marketed in two main editions: the "Home"🫰 edition was targeted towards consumers, while the "Professional" edition was targeted towards business environments and power users, and included additional🫰 security and networking features. Home and Professional were later accompanied by the "Media Center" edition (designed for home theater PCs,🫰 with an emphasis on support for DVD playback, TV tuner cards, DVR functionality, and remote controls), and the "Tablet PC"🫰 edition (designed for mobile devices meeting its specifications for a tablet computer, with support for stylus pen input and additional🫰 pen-enabled applications).[38][39][40] Mainstream support for Windows XP ended on April 14, 2009. Extended support ended on April 8, 2014.[41]
After Windows🫰 2000, Microsoft also changed its release schedules for server operating systems; the server counterpart of Windows XP, Windows Server 2003,🫰 was released in April 2003.[35] It was followed in December 2005, by Windows Server 2003 R2.
Windows Vista
After a lengthy development🫰 process, Windows Vista was released on November 30, 2006, for volume licensing and January 30, 2007, for consumers. It contained🫰 a number of new features, from a redesigned shell and user interface to significant technical changes, with a particular focus🫰 on security features. It was available in a number of different editions, and has been subject to some criticism, such🫰 as drop of performance, longer boot time, criticism of new UAC, and stricter license agreement. Vista's server counterpart, Windows Server🫰 2008 was released in early 2008.
Windows 7
On July 22, 2009, Windows 7 and Windows Server 2008 R2 were released to🫰 manufacturing (RTM) and released to the public three 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.[42] Windows🫰 7 has multi-touch support, a redesigned Windows shell with an updated taskbar with revealable jump lists that contain shortcuts to🫰 files frequently used with specific applications and shortcuts to tasks within the application,[43] a home networking system called HomeGroup,[44] and🫰 performance improvements.
Windows 8 and 8.1
Windows logo (2012–2024)
Windows 8, the successor to Windows 7, was released generally on October 26, 2012.🫰 A number of significant changes were made on Windows 8, including the introduction of a user interface based around Microsoft's🫰 Metro design language with optimizations for touch-based devices such as tablets and all-in-one PCs. These changes include the Start screen,🫰 which uses large tiles that are more convenient for touch interactions and allow for the display of continually updated information,🫰 and a new class of apps which are designed primarily for use on touch-based devices. The new Windows version required🫰 a minimum resolution of 1024×768 pixels,[45] effectively making it unfit for netbooks with 800×600-pixel screens.
Other changes include increased integration with🫰 cloud services and other online platforms (such as social networks and Microsoft's own OneDrive (formerly SkyDrive) and Xbox Live services),🫰 the Windows Store service for software distribution, and a new variant known as Windows RT for use on devices that🫰 utilize the ARM architecture, and a new keyboard shortcut for screenshots.[46][47][48][49][50][51][52] An update to Windows 8, called Windows 8.1,[53] was🫰 released on October 17, 2013, and includes features such as new live tile sizes, deeper OneDrive integration, and many other🫰 revisions. Windows 8 and Windows 8.1 have been subject to some criticism, such as the removal of the Start menu.
Windows🫰 10
On September 30, 2014, Microsoft announced Windows 10 as the successor to Windows 8.1. It was released on July 29,🫰 2024, and addresses shortcomings in the user interface first introduced with Windows 8. Changes on PC include the return of🫰 the Start Menu, a virtual desktop system, and the ability to run Windows Store apps within windows on the desktop🫰 rather than in full-screen mode. Windows 10 is said to be available to update from qualified Windows 7 with SP1,🫰 Windows 8.1 and Windows Phone 8.1 devices from the Get Windows 10 Application (for Windows 7, Windows 8.1) or Windows🫰 Update (Windows 7).[54]
In February 2024, Microsoft announced the migration of its Windows source code repository from Perforce to Git. This🫰 migration involved 3.5 million separate files in a 300-gigabyte repository.[55] By May 2024, 90 percent of its engineering team was🫰 using Git, in about 8500 commits and 1760 Windows builds per day.[55]
In June 2024, shortly before Microsoft's announcement of Windows🫰 11, Microsoft updated their lifecycle policy pages for Windows 10, revealing that support for their last release of Windows 10🫰 will end on October 14, 2025.[56][57] On April 27, 2024, Microsoft announced that version 22H2 would be the last of🫰 Windows 10.[59]
Windows 11
On June 24, 2024, Windows 11 was announced as the successor to Windows 10 during a livestream. The🫰 new operating system was designed to be more user-friendly and understandable. It was released on October 5, 2024.[60][61] As of🫰 May 2024, Windows 11 is a free upgrade to Windows 10 users who meet the system requirements.[62]
Windows 365
In July 2024,🫰 Microsoft announced it will start selling subscriptions to virtualized Windows desktops as part of a new Windows 365 service in🫰 the following month. The new service will allow for cross-platform usage, aiming to make the operating system available for both🫰 Apple and Android users. It is a separate service and offers several variations including Windows 365 Frontline, Windows 365 Boot,🫰 and the Windows 365 app.[63] The subscription service will be accessible through any operating system with a web browser. The🫰 new service is an attempt at capitalizing on the growing trend, fostered during the COVID-19 pandemic, for businesses to adopt🫰 a hybrid remote work environment, in which "employees split their time between the office and home". As the service will🫰 be accessible through web browsers, Microsoft will be able to bypass the need to publish the service through Google Play🫰 or the Apple App Store.[64][65][66][67][68]
Microsoft announced Windows 365 availability to business and enterprise customers on August 2, 2024.[69]
Multilingual support
Multilingual support🫰 has been built into Windows since Windows 3.0. The language for both the keyboard and the interface can be changed🫰 through the Region and Language Control Panel. Components for all supported input languages, such as Input Method Editors, are automatically🫰 installed during Windows installation (in Windows XP and earlier, files for East Asian languages, such as Chinese, and files for🫰 right-to-left scripts, such as Arabic, may need to be installed separately, also from the said Control Panel). Third-party IMEs may🫰 also be installed if a user feels that the provided one is insufficient for their needs. Since Windows 2000, English🫰 editions of Windows NT have East Asian IMEs (such as Microsoft Pinyin IME and Microsoft Japanese IME) bundled, but files🫰 for East Asian languages may be manually installed on Control Panel.
Interface languages for the operating system are free for download,🫰 but some languages are limited to certain editions of Windows. Language Interface Packs (LIPs) are redistributable and may be downloaded🫰 from Microsoft's Download Center and installed for any edition of Windows (XP or later) – they translate most, but not🫰 all, of the Windows interface, and require a certain base language (the language which Windows originally shipped with). This is🫰 used for most languages in emerging markets. Full Language Packs, which translate the complete operating system, are only available for🫰 specific editions of Windows (Ultimate and Enterprise editions of Windows Vista and 7, and all editions of Windows 8, 8.1🫰 and RT except Single Language). They do not require a specific base language and are commonly used for more popular🫰 languages such as French or Chinese. These languages cannot be downloaded through the Download Center, but are available as optional🫰 updates through the Windows Update service (except Windows 8).
The interface language of installed applications is not affected by changes in🫰 the Windows interface language. The availability of languages depends on the application developers themselves.
Windows 8 and Windows Server 2012 introduce🫰 a new Language Control Panel where both the interface and input languages can be simultaneously changed, and language packs, regardless🫰 of type, can be downloaded from a central location. The PC Settings app in Windows 8.1 and Windows Server 2012🫰 R2 also includes a counterpart settings page for this. Changing the interface language also changes the language of preinstalled Windows🫰 Store apps (such as Mail, Maps and News) and certain other Microsoft-developed apps (such as Remote Desktop). The above limitations🫰 for language packs are however still in effect, except that full language packs can be installed for any edition except🫰 Single Language, which caters to emerging markets.
Platform support
Windows NT included support for several 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🫰 of the platforms implement 64-bit computing, the OS treated them as 32-bit). Windows 2000 dropped support for all platforms, except🫰 the third generation x86 (known as IA-32) or newer in 32-bit mode. The client line of the Windows NT family🫰 still runs on IA-32 but the Windows Server line 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 2003, is the last Windows client operating system to support Itanium. Windows Server line continues 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 x86-64🫰 (or simply x64), the 64-bit version 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, and while ARM is still used for Windows smartphones with Windows 10,🫰 tablets with Windows RT will not be updated. Starting from Windows 10 Fall Creators Update (version 1709) and later includes🫰 support for ARM-based PCs.[70]
Windows 11 is the first version to drop support for 32-bit hardware.[62]
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.
Xbox OS
Xbox OS is an unofficial name given to🫰 the version of Windows that runs on Xbox consoles.[71] From Xbox One onwards it is an implementation with an emphasis🫰 on virtualization (using Hyper-V) as it is three operating systems running at once, consisting of the core operating system, a🫰 second implemented for games and a more Windows-like environment for applications.[72] Microsoft updates Xbox One's OS every month, and these🫰 updates can be downloaded from the Xbox Live service to the Xbox and subsequently installed, or by using offline recovery🫰
downloaded via a PC.[73] It was originally based on NT 6.2 (Windows 8) kernel, and the latest version runs🫰 on an NT 10.0 base. This system is sometimes referred to as "Windows 10 on Xbox One".[74][75] Xbox One and🫰 Xbox Series operating systems also allow limited (due to licensing restrictions and testing resources) backward compatibility with previous generation hardware,[76]🫰 and the Xbox 360's system is backwards compatible with the original Xbox.[77]
Version control system
Up to and including every version before🫰 Windows 2000, Microsoft used an in-house version control system named Source Library Manager (SLM). Shortly after Windows 2000 was released,🫰 Microsoft switched to a fork of Perforce named Source Depot.[78] This system was used up until 2024 once the system🫰 could not keep up with the size of Windows.[citation needed] Microsoft had begun to integrate Git into Team Foundation Server🫰 in 2013,[79] but Windows (and Office) continued to rely on Source Depot.[80] The Windows code was divided among 65 different🫰 repositories with a kind of virtualization layer to produce unified view of all of the code.[citation needed]
In 2024 Microsoft announced🫰 that it would start using Git, an open source version control system created by Linus Torvalds and in May 2024🫰 they reported that the migration into a new Git repository was complete.[81][82][55]
VFSForGit
Because of its large, decades-long history, however, the Windows🫰 codebase is not especially well suited to the decentralized nature of Linux development that Git was originally created to manage.[citation🫰 needed] Each Git repository contains a complete history of all the files,[83] which proved unworkable for Windows developers because cloning🫰 the whole repository takes several hours.[citation needed] Microsoft has been working on a new project called the Virtual File System🫰 for Git (VFSForGit) to address these challenges.[82]
In 2024 the VFS for Git has been superseded by Scalar.[84]
Timeline of releases
Windows timeline:🫰 Bar chart
The Windows family tree
Usage share and device sales
Use of Windows 10 has exceeded Windows 7 globally since early 2024.[91]
For🫰 desktop and laptop computers, according to Net Applications and StatCounter (which track the use of operating systems in devices that🫰 are active on the Web), Windows was the most used operating-system family in August 2024, with around 91% usage share🫰 according to Net Applications[92] and around 76% usage share according to StatCounter.[93]
Including personal computers of all kinds (e.g., desktops, laptops,🫰 mobile devices, and game consoles), Windows OSes accounted for 32.67% of usage share in August 2024, compared to Android (highest,🫰 at 46.03%), iOS's 13.76%, iPadOS's 2.81%, and macOS's 2.51%, according to Net Applications[94] and 30.73% of usage share in August🫰 2024, compared to Android (highest, at 42.56%), iOS/iPadOS's 16.53%, and macOS's 6.51%, according to StatCounter.[95]
Those statistics do not include servers🫰 (including so-called cloud computing, where Microsoft is known not to be a leader, with Linux used more than Windows) as🫰 Net Applications and StatCounter use web browsing as a proxy for all use.
Security
Early versions of Windows were designed at a🫰 time where malware and networking were less common, and had few built-in security features; they did not provide access privileges🫰 to allow a user to prevent other users from accessing their files, and they did not provide memory protection to🫰 prevent one process from reading or writing another process's address space or to prevent a process from code or data🫰 used by privileged-mode code.
While the Windows 9x series offered the option of having profiles for multiple users with separate profiles🫰 and home folders, it had no concept of access privileges, allowing any user to edit others' files. In addition, while🫰 it ran separate 32-bit applications in separate address spaces, protecting an application's code and data from being read or written🫰 by another application, it did not protect the first megabyte of memory from userland applications for compatibility reasons. This area🫰 of memory contains code critical to the functioning of the operating system, and by writing into this area of memory🫰 an application can crash or freeze the operating system. This was a source of instability as faulty applications could accidentally🫰 write into this region, potentially corrupting important operating system memory, which usually resulted in some form of system error and🫰 halt.[96]
Windows NT was far more secure, implementing access privileges and full memory protection, and, while 32-bit programs meeting the DoD's🫰 C2 security rating,[97] yet these advantages were nullified[improper synthesis?] by the fact that, prior to Windows Vista, the default user🫰 account created during the setup process was an administrator account; the user, and any program the user launched, had full🫰 access to the machine. Though Windows XP did offer an option of turning administrator accounts into limited accounts, the majority🫰 of home users did not do so, partially due to the number of programs which required administrator rights to function🫰 properly. As a result, most home users still ran as administrator all the time. These architectural flaws, combined with Windows's🫰 very high popularity, made Windows a frequent target of computer worm and virus writers.[98][99][citation needed]
Furthermore, although Windows NT and its🫰 successors are designed for security (including on a network) and multi-user PCs, they 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.[100]
In a🫰 2002 strategy memo entitled "Trustworthy computing" sent to every Microsoft employee, Bill Gates declared that security should become Microsoft's highest🫰 priority.[101][102]
Windows Vista introduced a privilege elevation system called User Account Control.[103] 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.[104]
Leaked documents from 2013 to 2024 codenamed Vault 7 detail the capabilities of the CIA to perform electronic🫰 surveillance and cyber warfare,[105] such as the ability to compromise operating systems such as Windows.[106]
In August 2024, computer experts reported🫰 that the BlueKeep security vulnerability, CVE-2024-0708, that potentially affects older unpatched Windows versions via the program's Remote Desktop Protocol, allowing🫰 for the possibility of remote code execution, may include related flaws, collectively named DejaBlue, affecting newer Windows versions (i.e., Windows🫰 7 and all recent versions) as well.[107] In addition, experts reported a Microsoft security vulnerability, CVE- 2024-1162, based on legacy🫰 code involving Microsoft CTF and ctfmon (ctfmon.exe), that affects all Windows versions from Windows XP to the then most recent🫰 Windows 10 versions; a patch to correct the flaw is available.[108]
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.[109] Versions subsequent to Windows 2000 SP3 and Windows XP implemented automatic download and installation of updates, substantially increasing the🫰 number of users installing security updates.[110]
Windows integrates the Windows Defender antivirus, which is seen as one of the best available.[111]🫰 Windows also implements Secure Boot, Control Flow Guard, ransomware protection, BitLocker disk encryption, a firewall, and Windows SmartScreen.
File permissions
All Windows🫰 versions from Windows NT 3 have been based on a file system permission system referred to as AGDLP (Accounts, Global,🫰 Domain Local, Permissions) in which 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 directly 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.
Alternative implementations
Owing to the operating system's popularity, a number of applications have been released that aim to🫰 provide compatibility with Windows applications, either as a compatibility layer for another operating system, or as a standalone system that🫰 can run software written for Windows out of the box. 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 macOS. Wine developers refer🫰 to it as a "compatibility layer" [112] and use Windows-style APIs to emulate Windows environment. CrossOver – a Wine package🫰 with licensed fonts. Its developers are regular contributors to Wine. Proton – A fork of Wine by Steam to run🫰 Windows games on Linux and other Unix-like OS.
and use Windows-style APIs to emulate Windows environment. ReactOS – an open-source OS🫰 intended to run the same software as Windows, originally designed to simulate Windows NT 4.0, later aiming at Windows 7🫰 compatibility. It has been in the development stage since 1996.
See also
