According to Hal Berenson , Microsoft’s “Operating Systems Engineering” Group, under Terry Myerson, which encompasses most of what used to be known as the “Windows Division”, is split into three main categories:
Terry essentially split Windows into three (ignoring the consumer services work under Chris Jones): Windows and Windows Phone, Xbox, and “Core OS”. Wait a moment you say, what is this Core OS thing? Well, that is the thing that Terry kept functional to him. The work that is shared across all Windows platforms belongs to the organization that has David Treadwell running Program Management, Henry Sanders running Development, and Mike Fortin running Test.