Windows NT

Windows NT is a major family of proprietary graphical operating systems. An operating system is the core software that manages a computer's hardware and software. Microsoft first released the first version, Windows NT 3.1, on July 27, 1993. Originally, this system was built for professional workstations, offices, and large servers. It was designed to be much more powerful than consumer versions. Eventually, Microsoft moved this advanced technology into home computers with Windows XP in 2001. Today, the underlying technology still exists in modern systems like Windows Server 2025.

The architecture of Windows NT uses a layered design with two main parts. These parts are called user mode and kernel mode.

Programs running in user mode have limited access to system resources. This limitation helps protect the computer if a program makes a mistake. In contrast, kernel mode has unrestricted access to all system memory and external devices. The Windows NT kernel is specifically called a hybrid kernel. It combines a simple kernel with a Hardware Abstraction Layer, known as the HAL. The HAL allows the software to work on many different types of computer processors. The kernel also works with a group of services called the Executive. All these parts exist together in kernel mode to manage the machine.

Windows NT introduced several technical advancements that changed how computers functioned. One major change was the move to 32-bit memory addressing. Earlier versions of Windows, like Windows 3.1, used 16-bit memory access which had strict limitations. Windows NT 3.1 used a 32-bit flat virtual memory addressing system. This allowed the computer to handle much more data at once. The system also included a secure file system called NTFS, which stands for New Technology File System. NTFS is a journaled system that helps keep files organized and safe. Newer versions of the technology have even moved to 64-bit computing. This allows for 64-bit kernels and 64-bit memory addressing to increase speed and capacity.

Developing Windows NT was a complex process involving many different companies. Microsoft began planning a portable operating system in October 1988. At first, the project was called "NT OS/2" because it was meant to be a joint project with IBM. The team wanted the system to support multiprocessing and different types of software. However, tensions grew between Microsoft and IBM over technical decisions. Microsoft decided to change the programming interface to a Windows API instead of an OS/2 API. This led to the partnership falling apart. Microsoft continued the work alone and renamed the project Windows NT. This decision helped Windows NT eventually become more successful than OS/2.

The creation of the system was led by a group of expert developers. This team was led by Dave Cutler, who had previously worked at Digital Equipment Corporation. These developers brought experience from older systems like VMS, VAX/VMS, and RSX-11. Because of this influence, the internal structures of Windows NT are very similar to VMS. In fact, some parts of the Windows NT code look like a previous system called MICA. This similarity led to a legal settlement where Microsoft paid DEC between $65 million and $100 million. The development team also included members from the disbanded OS/2 team, such as Moshe Dunie. This mix of expertise helped build a very stable foundation.

There is also much debate regarding the meaning of the name "NT." Some suggest the name was a play on the VMS system by incrementing letters. Other developers, like Mark Lucovsky and Dave W. Plummer, believe it came from the Intel i860 processor. This processor had the code name N10, or "N-Ten." In 1991, Bill Gates stated that NT stood for "New Technology." However, in a 1998 Q&A session, he revealed that the letters no longer carried a specific meaning. The "NT" label was also removed from product names starting with Windows 2000. Even though the name was dropped, Microsoft noted that these products were still "Built on NT Technology."

Windows NT was designed to be highly portable across different hardware. This means it could run on many different types of computer "brains" or architectures. Early versions supported IA-32, MIPS, and DEC Alpha processors. Later releases added support for PowerPC, Itanium, x86-64, and ARM. To make this work, the system used a common code base with a custom Hardware Abstraction Layer for each platform. The system also provided different software environments to ensure compatibility. It could support Windows API, POSIX, and OS/2 APIs. This allowed the operating system to run many different kinds of programs.