confidential documents. A virtual memory management was designed to thwart attacks by malware and prevent users from accessing foreign areas of memory. The third goal was called personality: The operating system should be able to run applications designed for various operating systems, such as Windows, MS-DOS and OS/2 applications. The Mach kernel followed a similar concept by moving the APIs to components which operated in user mode as applications, these could be changed and new ones could be added. This principle was applied to Windows NT. Despite all these goals, the performance of the operating system was optimized where possible, by adapting critical sections of the code to fast execution speed. To improve networking performance, large parts of the networking system were moved to the operating system core. Windows NT was designed as a networking operating system. In this branch, Novell had a lead with its product NetWare, mostly because of a lack of competition, and Microsoft failed to develop a product which could challenge NetWare's lead. Cutler hoped to gain additional customers with a reliable networking operating system. Bill Gates already dominated the market of desktop operating systems with MS-DOS and Windows and hoped to do the same in the networking market with Windows NT. He especially hoped to find a market in the emerging number of servers, while at the same time he did not expect a success in the desktop market until 1995. Therefore, Windows NT was positioned as a high-end operating system in an interview with the product manager David Thacher. It was not designed to replace Windows 3.1 completely, but it should rather supplement Microsoft's product palette with an operating system for critical applications. The expectations were 10% to 20% among all Windows sales and a market share of 10% in the high end market, which amounted to one million copies. Features Architecture While Windows NT 3.1 uses the same graphical user interface as Windows 3.1, it was developed anew. The operating system is not DOS-based, but an independent 32-bit operating system; many concepts were taken from Cutler's previous operating system, VMS. The architecture of Windows NT takes some ideas of the client–server model, like the modular structure and the communication between the modules. System resources like memory, files or devices are viewed as objects by the operating system, which are all accessed in the same way through handles and which can in this way