Windows RT is a mobile operating system developed by Microsoft and released alongside Windows 8 on October 26, 2012. It is a version of Windows 8 or Windows 8.1 built for the 32-bit ARM architecture (ARMv7), designed 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. Unlike Windows 8, Windows RT was only available as preloaded software on devices specifically designed for the operating system by original equipment manufacturers (OEMs); Microsoft launched its own hardware running it, the Surface tablet, which was followed by Surface 2, although only five models running Windows RT were released by third-party OEMs throughout its lifetime.