MS Windows NT Kernel-Mode User and GDI

Microsoft Windows NT Workstation 4.0 and Windows NT Server 4.0 include a change in the implementation of Win32 graphics-related application programming interfaces. These changes are transparent to applications and users, yet result in a variety of improvements to graphics performance and memory requirements, as well as simplifying the design of the Windows NT Win32 subsystem. The improvements result from the move of certain operating system modules from a user-mode application process into a subsystem within the privileged portion of Windows NT, known as the Executive.