Windows NT 3.1 - Operating System Goals

Operating System Goals

Cutler set three main goals for Windows NT. The first goal was portability: in contrast to previous operating systems, which were strongly tied to one architecture, Windows NT should be able to operate on multiple architectures. To meet this goal, most of the operating systems, including the operating system core, had to be written in the C programming language. During the planning phase it was clear that this would cause Windows NT to have a higher memory consumption than all previous operating systems. Besides the graphics system and parts of the networking system, which were written in C++, only parts of the operating systems which required direct hardware access and performance critical functions were written in assembly language. These parts were isolated so that they could easily be rewritten when porting the operating system to a new architecture.

The second goal was reliability: The system should no longer crash due to a faulty application or faulty hardware. This way, the operating system should be made attractive for critical applications. To meet this goal, the architecture of Windows NT was designed so that the operating system core was isolated and applications could not access it directly. The kernel was designed as a microkernel and components of the core were to run atop the kernel in a modular fashion; Cutler knew this principle from his work at Digital. Reliability also includes security, and the operating system should be able to resist external attacks. Mainframes already had a system where every user had their own account which was assigned specific rights by the administrator, this way, users could be prevented access to 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 opeating 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 amount 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 Paul 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.