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| other_articles = * Features new to Windows 8 * List of features removed in Windows 8 * Windows 8 editions * Windows Store |date=October 2012}} Windows RT is an operating system for mobile devices developed by Microsoft. It is essentially an edition of Windows 8.x built for the 32-bit ARM architecture (ARMv7). First unveiled as a prototype in January 2011 at Consumer Electronics Show, the Windows 8 RT operating system was officially launched alongside Windows 8 on October 26, 2012, with the release of three Windows RT-based devices, including Microsoft's Surface tablet. Unlike Windows 8, Windows RT is only available as pre-loaded software on devices specifically designed for the operating system by OEMs. Microsoft intended for devices with Windows RT to take advantage of the architecture's power efficiency to allow for longer battery life, to use system-on-chip (SoC) designs to allow for thinner devices, and to provide a "reliable" experience over time. In comparison to other mobile operating systems, Windows RT also supports a relatively large number of existing USB peripherals and accessories, and includes a version of Microsoft Office 2013 optimized for ARM devices as pre-loaded software. However, while Windows RT inherits the appearance and functionality of Windows 8, it has a number of limitations; it can only execute software that is digitally signed by Microsoft (which includes pre-loaded software and Windows Store apps), and it lacks certain developer-oriented features. Windows RT was released to mixed reviews from various outlets and critics. Some felt that Windows RT devices had advantages over other mobile platforms (such as iOS or Android) because of its bundled software and the ability to use a wider variety of USB peripherals and accessories, but the platform was criticized for its poor software ecosystem, citing the early state of Windows Store and its incompatibility with existing Windows software, and other limitations over Windows 8. Critics and analysts deemed Windows RT to be commercially unsuccessful, citing these limitations, its unclear, uncompetitive position of sitting as an underpowered system between Windows Phone and Windows 8, and the introduction of Windows 8 devices with battery life and functionality that met or exceeded that of Windows RT devices. Improvements to Intel's mobile processors, along with a decision by Microsoft to remove OEM license fees for Windows on devices with screens smaller than 9 inches, spurred a market for low-end Wintel tablets running the full Windows 8 platform that cannibalized Windows RT. Vendors quickly began phasing out their Windows RT devices due to poor sales, and less than a year after its release, Microsoft suffered a US$900 million loss that was largely blamed on poor sales of the ARM-based Surface tablet and unsold stock. Only two more Windows RT devices, the Microsoft Surface 2 and Nokia Lumia 2520 in late-2013, were released outside of the five original launch devices, and no Windows RT counterpart of the Surface Pro 3 was released due to a re-positioning of the Surface line into a high-end market, and a switch to Intel architecture for the Surface 3. These developments left Microsoft's future support of the platform in doubt. As of February 2015, with the end of production for both Surface 2 and Lumia 2520, Microsoft and its subsidiaries no longer manufacture any Windows RT devices.〔〔 There is no equivalent to Windows RT for Windows 10, and Microsoft does not consider Windows RT devices to be compatible with Windows 10.〔(【引用サイトリンク】url=http://www.pcmag.com/article2/0,2817,2478431,00.asp )〕〔(【引用サイトリンク】title=Windows 10 specifications )〕 Windows 10 Mobile, based on Windows Phone, was unveiled for use on tablets and smartphones with ARM architecture. == History == At the 2011 Consumer Electronics Show, it was officially announced that the next version of Windows would provide support for system-on-chip (SoC) implementations based on the ARM architecture. Steven Sinofsky, then Windows division president, demonstrated an early version of a Windows port for the architecture, codenamed Windows on ARM (WoA), running on prototypes with Qualcomm Snapdragon, Texas Instruments OMAP, and Nvidia Tegra 2 chips. The prototypes featured working versions of Internet Explorer 9 (with DirectX support via the Tegra 2's GPU), PowerPoint and Word, along with the use of class drivers to allow printing to an Epson printer. Sinofsky felt that the shift towards SoC designs were "a natural evolution of hardware that's applicable to a wide range of form factors, not just to slates", while Microsoft CEO Steve Ballmer emphasized the importance of supporting SoCs on Windows by proclaiming that the operating system would "be everywhere on every kind of device without compromise." Initial development on WoA took place by porting code from Windows 7; Windows Mobile smartphones were used to test early builds of WoA because of lack of readily available ARM-based tablets. Later testing was performed using a custom-designed array of rack-mounted ARM-based systems.〔 Changes to the Windows codebase were made to optimize the OS for the internal hardware of ARM devices, but a number of technical standards traditionally used by x86 systems are also used. WoA devices would use UEFI firmware, and have a software-based Trusted Platform Module to support device encryption and UEFI Secure Boot. ACPI is also used to detect and control plug and play devices and provide power management outside the SoC. To enable wider hardware support, peripherals such as human interface devices, storage and other components that use USB and I²C connections use class drivers and standardized protocols. Windows Update serves as the mechanism for updating all system drivers, software, and firmware. Microsoft showcased other aspects of the new operating system, to be known as Windows 8, during subsequent presentations. Among these changes (which also included an overhauled interface optimized for use on touch-based devices built around Metro design language) was the introduction of Windows Runtime (WinRT). Software developed using this new architecture could be processor-independent (allowing compatibility with both x86 and ARM-based systems),〔 would emphasize the use of touch input, would run within a sandboxed environment to provide additional security, and be distributed through Windows Store—a store similar to services such as the App Store and Google Play. WinRT was also optimized to provide a more "reliable" experience on ARM-based devices; as such, backwards compatibility for Win32 software otherwise compatible with older versions of Windows was intentionally excluded from Windows on ARM. Windows developers indicated that existing Windows applications were not specifically optimized for reliability and energy efficiency on the ARM architecture, and that WinRT was sufficient for providing "full expressive power" for applications, "while avoiding the traps and pitfalls that can potentially reduce the overall experience for consumers." Consequentially, this lack of backwards compatibility would also prevent existing malware from running on the operating system.〔 On April 16, 2012, Microsoft announced that Windows on ARM would be officially branded as Windows RT. Microsoft did not explicitly indicate what the "RT" in the operating system's name referred to, but it was believed to refer to the WinRT architecture. Steven Sinofsky stated that Microsoft would ensure the differences between Windows RT and 8 were adequately addressed in advertising. However, reports found that promotional web pages for the Microsoft Surface tablet had contained confusing wording alluding to the compatibility differences, and that Microsoft Store representatives were providing inconsistent and sometimes incorrect information about Windows RT. In response, Microsoft stated that Microsoft Store staff members would be given an average of 15 hours of training prior to the launch of Windows 8 and Windows RT to ensure consumers are able to make the correct choice for their needs. The first Windows RT devices were officially released alongside Windows 8 on October 26, 2012. Windows 8.1, an upgrade for Windows 8 and RT, was released in Windows Store on October 17, 2013, containing a number of improvements to the operating system's interface and functionality. For Windows RT devices, the update also adds Outlook to the included Office RT suite. The update was temporarily recalled by Microsoft shortly after its release, following reports that some Surface users had encountered a rare bug which corrupted their device's Boot Configuration Data during installation, resulting in an error on startup.〔(【引用サイトリンク】url=http://www.pcworld.com/article/2056283/microsoft-temporarily-pulls-windows-rt-8-1-update-due-to-a-situation.html )〕 On October 21, 2013, Microsoft released recovery media and instructions which could be used to repair the device, and restored access to Windows 8.1 the next day.〔(【引用サイトリンク】url=http://www.pcworld.com/article/2056295/microsoft-releases-fix-for-surface-rt-slates-borked-by-windows-rt-8-1-update.html )〕〔(【引用サイトリンク】url=http://www.pcworld.com/article/2056548/microsoft-fixes-windows-rt-8-1-issues-returns-update-to-windows-store.html )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Windows RT」の詳細全文を読む スポンサード リンク
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