The much-anticipated Windows Core OS is currently being prepared for “next-gen” Microsoft devices; which include the Surface Hub, HoloLens and the upcoming folding devices.

This is implied in the LinkedIn profile summary of a Microsoft Software Engineer:

Experienced C++ developer with expertise in Cloud Manageable Operating Systems development. Delivering Azure-powered device management capabilities and protocols across IoT devices, next-gen WCOS devices, Windows Desktop, HoloLens and Windows Server

Another LinkedIn profile belonging to a software developer on the Windows Storage Spaces Team at Microsoft mentions the implementation of Windows Storage Spaces:

Backspace internal APIs for the management of Spaces with up level metadata versions on down level versions of Win dows for WCOS (Windows Core OS).

Storage Spaces is a technology in Windows and Windows Server that can help protect your data from drive failures. The feature would be part of increasing the resilience of Windows devices and making it more appliance-like.

WCOS has also been mentioned in LinkedIn job postings. Multiple profiles have indicated a new Action Center in Windows Core OS, and hint towards open source components.

With Microsoft’s commitment to the future development of Windows increasingly in question, it’s good to see that work is still ongoing with this paradigm-shifting project, which will once again attempt to create a Windows for extremely mobile devices.

Source: Windowslatest