Understanding the Origins of Windows NT

During the 1980s and early 1990s, Novell cornered the network operating system market. Microsoft offered networking software-OS/2 (which was originally developed by IBM) and LAN Manager-but these operating systems never really caught on.

Microsoft decided to create a new operating system from the ground up. Designing a new operating system would eliminate the inherent limitations of older software. In late 1988, Microsoft hired Dave Cutler, a veteran of minicomputer systems architecture, from Digital Equipment Corporation, to design the new network operating system. This 'New Technology' was to become Windows NT.

Before the programmers could begin creating this new operating system, the design team had to come up with the software design goals that would define what the NT operating system should do. The following subsections describe these goals.

Provide Flexibility in OS Code

The operating system code had to be written so that it could easily be modified to accommodate market demands.

In this sense, NT is fairly flexible-new software components can be added and deleted as current software and hardware standards dictate. New services and drivers can be written as standards change, and they do not affect the core operating system. Also, you can configure each server or workstation to use only the services and drivers that each unique configuration requires.

Offer High Performance

A major design goal of NT was that it had to be a high-performance operating system. Each component of NT has been optimized to provide the highest performance for individual use and on a network, including large networks with thousands of users.

Be Reliable

The operating system had to be able to handle errors in a reliable and fault-tolerant manner. This means that NT shields itself from most hardware and software errors so that the system will continue to operate.

New Technology File System (NTFS)

Developed by Microsoft for the NT operating systems, this feature added better file management, larger disk compatibility, and file-level security on the local computer.

Memory is one area where reliability is critical. NT manages memory through virtual memory. Virtual memory is the combination of physical RAM and the page file-a special file on the hard drive that is used to supplement physical RAM. Whenever you launch an application (with the exception of older Windows 16-bit applications), the memory manager in NT allocates the application its own separate memory space in RAM. The allocated portion cannot be used by any other program until the first application closes. This technique keeps a failed application from crashing or interfering with the operation of other applications or with the operating system.

The New Technology File System (NTFS) is also designed so that it is able to recover from many types of file errors.

Use Portable Code

As hardware standards change, NT should be able to be moved from one processor type to another. For example, NT can run on an Intel processor or an Alpha processor.

Be Compatible with Existing Standards

Another goal was that NT needed to be compatible with existing standards. This compatibility would make NT a better choice for computer networks with several types of operating systems coexisting (not just Microsoft operating systems). In addition, NT needed to be able to support existing applications that were written to run under other operating systems, particularly older Windows applications.

NT is compatible with existing network standards. For example, NT supports networking transport protocols such as TCP/IP, IPX/SPX, and NetBEUI. (TCP/IP and IPX/SPX are covered in Chapter 10, 'Data-Link and Network Layer Protocols.') NT also is compatible with other network operating systems, such as NetWare, Systems Network Architecture (SNA), Unix, and AppleTalk networks.

In addition, NT supports applications by providing modular subsystems for DOS, OS/2, and POSIX applications. As new standards emerge, new subsystems can be developed. Each configuration loads only the necessary subsystems. This level of modularity means that only parts of the operating system need to be changed; the entire software code for NT does not have to be rewritten.