Windows RT

In comparison to other mobile operating systems, Windows RT also supported 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. Some limitations it had compared to Windows 8 was that it could only execute software digitally signed by Microsoft, lacked certain developer-oriented features, and could not run applications designed for x86 processors, which were the main platform for Windows at the time. Windows RT 8.1 was released in 2013 as a free upgrade, featuring a number of improvements.
It received mixed reviews at launch, while critics and analysts deemed it to be commercially unsuccessful. It was criticized for its poor software ecosystem, citing the early stage of Windows Store and its incompatibility with existing Windows software. Some felt Windows RT devices had advantages over other mobile platforms (such as Android, iOS, and Microsoft's Windows Phone) because of its bundled software, and the ability to use a wider variety of USB peripherals and accessories.
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, giving battery life and functionality that met or exceeded that of Windows RT devices; these effectively cannibalized Windows RT sales, and was a reason why Microsoft suffered a US$900 million loss in July 2013. With the release of Surface 3 in 2015, the Surface line switched to Intel processors. In 2018, Microsoft would partner with Qualcomm on launching an ARM version of Windows 10; unlike Windows RT, the OS would support running x86 software via emulation. Provided by Wikipedia