In this release of Windows NT, the Window Manager (USER) and Graphics Device Interface (GDI) have been moved from the Win32 subsystem to the Windows NT Executive. Win32 user-mode device drivers, including graphics display and printer drivers, have also been moved to the Executive. These changes are designed to simplify graphics handling, reduce memory requirements, and improve performance.
An illustration of the architecture of Windows NT 3.51 and an illustration of the architecture of Windows NT 4.0 appear on facing pages on the inside back cover of this book.