Windows 8.1 is a version of Windows NT family of operating systems and an upgrade for Windows 8. First unveiled and released as a public beta in June 2013, it was released to manufacturing on August 27, 2013, and reached general availability on October 17, 2013, almost a year after the retail release of its predecessor. Windows 8.1 is available free of charge for retail copies of Windows 8 and Windows RT users via Windows Store. Users who obtained 8 outside of retail copies or pre-loaded installations (i.e., volume licensing) must obtain 8.1 through new installation media from their respective subscription or enterprise channel. According to Microsoft's software lifecycle policies, installation of Windows 8.1 is required to maintain access to Windows 8's mainstream support after January 12