Windows 10 is a personal computer operating system developed by Microsoft as part of the Windows NT family of operating systems. Unveiled on September 30, 2014, it is expected to fully be released in between mid and late 2015, and is currently in public beta testing. Microsoft released the January technical preview of Windows 10 unveiling numerous features including the Continum and Cortana assist for PC and much more. For its first year of availability, Windows 10 will be offered at no charge for devices running its predecessors, Windows 8.1 and Windows 7.