November 20, 1985
Windows -- originally codenamed Interface Manager -- was announced by Bill Gates in 1983, but didn't ship until 20 November 1985. Its first incarnation was as a front end for Microsoft's command-line DOS, or Disk Operating System.
Windows 1.0 could only support tiled windows, but had desktop features such as the MS-DOS Executive file manager, Calendar, Cardfile, Notepad, Terminal, Calculator and Clock.
Utilities included RAMDrive, for managing memory cards designed to beat the PC's 640KB memory limit, Clipboard and Print Spooler. There was even a game, Reversi. In a special introductory offer, Windows 1.0 came with Windows Write and Windows Paint and cost $99.
For a longer look at Windows history, visit The History of Windows timeline.
December 9, 1987
The second version of Windows introduced overlapping windows and supported 16-colour VGA graphics. It marked the debut of the Control Panel and Program Information Files, or PIFs, that told Windows how to run DOS applications,. It was also the first Windows platform for Microsoft's Word and Excel applications.
Like Windows 1.0, version 2.0 could run on a dual-floppy-drive PC without a hard disk. It used the real-mode memory model, limiting memory access to 1MB.
Overlapping windows and other Mac-like features in Windows 2.0 resulted in an ultimately unsuccessful Apple lawsuit in 1988.
May 22, 1990
The first Windows version to achieve widespread use, Windows 3.0 saw significant user interface changes, as well as improved exploitation of the Intel 286 and 386 processors' memory management capabilities.
Program Manager and File Manager made their first appearance here, along with a redesigned Control Panel and Solitaire -- a Windows staple to this day. Everything looked better thanks to Windows 3.0's support for 256-colour VGA.
July 27, 1993
Windows NT was born from the wreckage of Microsoft's ill-fated OS/2 partnership with IBM. It was built from the ground up under the leadership of ex-DEC software engineer Dave Cutler as a fully 32-bit pre-emptive multitasking, multithreaded, multiprocessing, multiuser operating system with a hybrid kernel and a hardware abstraction layer to facilitate porting between processor platforms.
It was initially developed for the Intel i860, whose N-Ten codename gave NT its name, although later marketing-led revisionism changed this to New Technology. NT variants have appeared on many CPU architectures, including IA-32, x86-64, Alpha, MIPS, PowerPC, ARM and Itanium. Its code base still underpins the current generation of Windows operating systems.
August 24, 1995
Launched with an unprecedented marketing push that included the Rolling Stones song Start Me Up - whose lyrics, detractors gleefully pointed out, included the line, "You make a grown man cry" - Windows 95 was a consumer-oriented hybrid 32-bit/16-bit OS with a brand-new user interface and modern features like plug-and-play automatic device detection and configuration.
Windows 95's UI saw the first appearance of the long-running features such as the Start button and menu - hence Start Me Up - the taskbar and system tray or notification area, and maximise, minimise, close buttons on windows. The start-up jingle for Windows 95 was written by Brian Eno, ironically, on a Mac.
August 24, 1996
Available in Workstation and Server versions at launch, and followed by Server, Enterprise Edition in 1997 and Terminal Server in 1998, Windows NT 4.0 added the Windows 95 user interface to the fully 32-bit, business-oriented NT operating system.
Under the surface, NT 4.0 saw a number of architectural improvements. In particular, the Graphics Device Interface, or GDI, was moved into kernel mode, giving a significant performance boost over NT 3.5x, although this also required graphics and printer drivers to be updated. NT 4.0 was also the first Windows version to support the DirectX multimedia API.
June 25, 1998
Windows 98 was even more consumer-friendly than its predecessor Windows 95. A range of user-interface enhancements were introduced via the bundled Internet Explorer 4's Windows Desktop Update, including the Quick Launch toolbar, Active Desktop, the ability to minimise a window by clicking its toolbar icon, plus backward and forward buttons, and an address bar, in Windows Explorer.
USB support, first introduced with Windows 95 OSR2.1 in April 1997, was much improved in Windows 98, encompassing hubs, scanners, mice, keyboards and joysticks -- but not modems, printers or storage devices.
February 17, 2000
Built on the Windows NT 4.0 code base and designed to replace both NT 4.0 and Windows 98 - although Microsoft subsequently released the ill-starred Windows ME - Windows 2000 Professional brought significant improvements such as plug and play with full ACPI and WDM support, plus many features from the Windows 98/98 SE product line.
New across all Windows 2000 editions were NTFS 3.0, the Encrypting File System (EFS), Logical Disk Manager, an LDAP/Active Directory-enabled Address Book and the Microsoft Management Console (MMC). Windows File Protection prevented unauthorised programs from modifying critical system files.
September 14, 2000
The last of the DOS-based Windows 9x line, Millennium Edition is widely regarded as one of the worst Windows versions ever released.
Unlike Windows 95 and 98, it lacked real-mode DOS support, but did include the useful System Restore feature, which allowed users to take the system back to a previous stable configuration. Just as well, because the hurriedly released Windows ME was notorious for being buggy and crash-prone. It was quickly superseded by the far superior NT-based Windows XP.
Minimum system specifications for Windows ME were a 150MHz Pentium processor with 300MHz recommended, 32MB of RAM with 64MB recommended, and 320MB of hard disk space with 2GB recommended. It could address up to 1.5GB of RAM.
October 25, 2001
NT-based Windows XP succeeded the business-oriented Windows 2000 and the consumer-focused Windows ME, and initially came in Professional and Home versions. With a couple of Service Packs under its belt, XP - for 'eXPerience' - proved to be one of Microsoft's most successful Windows releases ever: extended support for this durable OS finally ended on April 8 2014 -- an unprecedented 12 and a half years after its launch.
The XP user interface featured an updated two-column Start menu, task-grouping support on the taskbar and the ability to lock the taskbar, among other enhancements -- all presented in a new default Luna visual style. Many other themes were available, including the classic Windows 95/2000 interface.
April 24, 2003
The server version of Windows XP came in Web, Standard, Enterprise, and Datacenter editions, and succeeded the respective editions of Windows Server 2000.
Key new features included Active Directory enhancements; the Manage Your Server tool for administrating server roles; version 6.0 of the IIS web server; better Group Policy handling and administration; a backup and restore system, plus improved disk management; and enhanced scripting and command-line tools.
January 30, 2007
Windows Vista had a convoluted gestation, a delayed birth, and a relatively short life, and retains a reputation as a particularly ill-conceived Windows release.
The main complaints centred on security features, digital rights management, hardware requirements and performance, and software compatibility.
After a false start on the XP code base, Longhorn (Vista's codename) was built on Windows Server 2003 SP1, having jettisoned key features such as WinFS. Despite an extensive beta test program, general availability of Vista came too late for the key Christmas 2006 PC-buying period.
Features that did ship included the Aero interface, which with the right hardware displayed transparent windows and other visual effects, and a redesigned Start menu.
February 27, 2008
Built on the same code base as Windows Vista, Windows Server 2008 included important new features like Network Access Protection (NAP), Server Core, PowerShell and Read-Only Domain Controllers. Existing components such as IIS, Terminal Services and the SMB file-sharing protocol also received thorough overhauls.
NAP checks that PCs connected to the network are compliant with IT policies, and takes appropriate action if they are not. Server Core installs a minimalist GUI and a limited set of server roles, to minimise RAM and patching requirements.
October 22, 2009
Windows 7 is widely regarded as the operating system that Vista should have been. It quickly made inroads into Vista's and XP's market share.
Windows 7's main new interface feature was the redesigned taskbar, featuring the translucent Aero look, thumbnail previews with live content, Jump Lists of recently-opened files and Aero Peek for minimising open application windows to view the desktop.
Other key improvements were a revamped Windows Media Player 12 with internet streaming support, a Device Stage for managing peripherals from one convenient location, fewer User Access Control prompts, faster indexing for the native search, improved touch functionality and a virtualised XP Mode for running legacy applications.
September 4, 2012
Windows Server 2012 came in four editions: Foundation, Essentials, Standard, and Datacenter. It offered significant advances in virtualisation, storage, networking and automation, positioning itself not only as an upgrade for traditional file/print/application/web servers, but also as an enabler of private, hybrid and public clouds - in combination with products such as System Center and Windows Azure.
WS 2012 could be installed in command-line Server Core mode or with the Windows 8 graphical interface, formerly known as Metro, or in a hybrid cut-down GUI mode.
Server Manager was the main GUI element, while PowerShell gained a multitude of cmdlets for managing in Server Core mode.
October 25, 2012
Windows 8 came in three 32-bit and 64-bit x86 editions: Windows 8, W8 Pro and W8 Enterprise - plus a fourth, Windows RT for ARM-based systems. The Enterprise edition was only available to Software Assurance customers, and included the Windows To Go feature for creating secure bootable USB flash drives. Pro and Enterprise, which can join Active Directory domains, were the business-oriented editions.
Microsoft's primary focus for Windows 8 was to accommodate touchscreen devices such as tablets and laptop/tablet hybrids, which it did via the flat, tile-based interface formerly known as Metro.
The traditional Windows 7-like Desktop, minus the Start button, was still present, but the system booted into the new-look Start screen.
October 17, 2013
Part of Microsoft's Blue-codenamed round of updates, the headline feature in Windows 8.1 was the partial restoration of the much-missed Start button on the desktop taskbar. It was not actually the classic Start button, but a visible button for accessing the more customisable Start screen.
You can also go straight to the desktop on login, and configure the desktop Start button or Windows key to go to the Apps page rather than the Start screen. Essentially a service pack for Windows 8, version 8.1 is a free download from the Windows Store.
Other new features in Windows 8.1 include enhanced search, more bundled Windows Store apps, the ability to display and use up to four apps side by side, deeper SkyDrive integration and a redesigned Windows Store.
July 29, 2015
Codenamed Threshold and extensively previewed since its unveiling in September 2014, Windows 10 reaches the general availability milestone on 29 July 2015. Widely seen as the Windows release to 'fix' Windows 8.x, whose confused Modern/Desktop UI was not well received, Windows 10 includes an expandable Start menu with Live Tiles, which is presented full-screen by default on touch-enabled devices. More generally, Windows 10 is designed to be a unifying release in which 'universal' apps, with appropriate UI behaviours, run on a wide range of platforms: embedded systems, smartphones, tablets, hybrid tablet/laptops, laptops, desktops and games consoles, as well as new hardware categories such as large-screen collaboration/presentation systems (Surface Hub) and AR/VR headsets (HoloLens).
New features include FIDO-based multi-factor authentication and improved support for biometric technologies (Windows Hello), a new default web browser (Microsoft Edge), the Cortana virtual personal assistant (previously introduced with Windows Phone 8.1) and DirectX 12/WDDM 2.0 for improved graphics and gaming functionality.
Windows 10 will be available in seven editions in total: Home, Mobile, Pro, Enterprise, Education, Mobile Enterprise and IoT Core. Users of 'qualifying' Windows 7, 8.1 and Phone 8.1 devices will be able to upgrade to the appropriate Windows 10 versions for free within a year of the launch, and will receive updates and security patches as they are released, in a scheme Microsoft calls 'Windows as a service'.