In the past, operating systems were designed around a single hardware platform such as Intel’s x86 family of processors. Unfortunately, this prevented the operating system from being capable of taking advantage of newer and more powerful hardware designs and chip types. Portability in NT means that it isn’t tied to any single architecture or technology; it can be “ported” to different types of hardware without being completely rewritten. This is possible because most of Windows NT is written in C, a highly portable programming language that is easily ported between different system architectures. NT also offers other portability features, which are described below.
Meet HAL
Windows NT has a modular, layered design that prevents hardware dependence. The only hardware-specific code resides in a special low-level component of the Windows NT kernel called the Hardware Abstraction Layer (HAL). Fortunately, HAL comprises only a small percentage of the entire NT operating system, so developing new HALs to support additional CPU architectures is a relatively easy process. HAL operates at the lowest level, translating low-level operating system functions into instructions understandable by the specific hardware used in the system. This universal, modular design is also the reason NT enjoys such a diverse array of hardware support, from notebook PCs to multi-CPU superservers.
Installable file systems
Another portability feature of NT is its ability to support many different file systems. Currently, NT supports the FAT (File Allocation Table used in DOS, Windows 95, and OS/2 systems), NTFS (Native Transactional File System introduced with Windows NT), and CDFS (CD-ROM File System). However, because of NT’s modular nature, support for additional file systems can be easily added in the future by simply creating new file system drivers and adding them to NT. This makes it relatively easy for NT to incorporate new technologies.
Note: Although not an installable file system per se, it is also possible to have NT support the Macintosh file system by creating a Macintosh-compatible volume under Windows NT Server.
COMPATIBILITY
The key to the acceptance of any operating system is its ability to work with existing systems and applications. Therefore, Microsoft designed NT to run a wide variety of different applications and interact with a number of different foreign operating systems.
Application subsystem design
Windows NT is capable of running many different types of applications, including MS-DOS, Windows 3.x (Win16), Windows 95 and NT (Win32), POSIX, and OS/2 1.x character-mode applications. Again, the modular design of NT makes it possible to support additional APIs in the future by simply adding new subsystems. An OS/2 Presentation Manager subsystem is also available as a separate add-on product for Windows NT.
Windows-on-Windows (WOW) subsystem
Windows NT offers 16-bit Windows application support using a subsystem known as the Windows-on-Windows 32 or WOW subsystem. WOW provides excellent Win16 compatibility by completely emulating a Windows 3.1 environment and offers the choice of running individual Windows 3.x applications in a shared or separate memory space. This support allows separate Win16 applications to communicate as seamlessly under NT as they did under Windows 3.x, using interprocess communications features such as DDE (Dynamic Data Exchange) and OLE (Object Linking and Embedding).
Interoperability with NetWare
Windows NT also provides excellent compatibility with Novell’s NetWare network operating system. In Windows NT 4.0, this support is embodied in several components:
NWLink, a NetWare compatible version of the IPX/SPX protocol.
Client Services for Netware (CSNW), a native NCP (NetWare Core Protocol) client that enables NT to access both NetWare 3.x and 4.x servers.
Gateway Services for NetWare (GSNW), a service that makes it possible (in NT Server only) to share NetWare file and print resources with non-NetWare clients.
File and Print Services for NetWare (FPNW), a separate add-on product that enables a Windows NT Server to appear to NetWare clients as a NetWare 3.x server.
Directory Service Manager for NetWare (DSMN), another add-on product that allows NetWare servers to participate in Windows NT’s native Directory Services.
In addition to these components, the Windows NT Server product also offers additional NetWare-centric features, including the ability to import NetWare user accounts and login scripts and provide NetWare compatible log-ins and log-in scripts for NetWare clients via FPNW.
Interoperability with UNIX
Windows NT is able to communicate with UNIX systems through its native support of the TCP/IP (Transmission Control Protocol/Internet Protocol) suite, TCP/IP printing, and the inclusion of basic TCP/IP connectivity applications such as FTP (File Transmission Protocol) and Telnet. Third-party products are also available that allow NT and UNIX systems to share files on shared network volumes. In addition, both NT Workstation and NT Server include Internet/intranet services such as HTTP (HyperText Transport Protocol), FTP, and Gopher servers (called Internet Information Server in NT Server and Peer Web Services in NT Workstation) to allow for cross-platform connectivity with UNIX and other TCP/IP-based systems.
Interoperability with Macintosh
Windows NT also offers significant support for Apple Macintosh computers. Both the Workstation and Server versions of NT support AppleTalk, the protocol used in Macintosh networks. Windows NT Server also allows for the creation of Macintosh name space on NTFS volumes to enable Mac/PC file sharing. Macintosh-related printing support in NT Server includes the ability for Macintosh systems to print to non-PostScript printers connected to the NT network, and PC users to send print jobs to PostScript printers on the AppleTalk network.
SCALABILITY
Another important aspect of Windows NT is the fact that it is a scalable operating system. This means that it can be used on a wide range of systems, from personal computers to large systems with multiple processors. These systems may have very little, or nothing, in common other than that they can all run Windows NT. Here’s a quick summary of NT’s scalability features:
Multiplatform support
Due to its layered, microkernel architecture and use of the Hardware Abstraction Layer, Windows NT is essentially open-ended in its ability to support new and more powerful processors as they are developed. This allows the same operating system to be used on systems of virtually any size or power, with no effective limits.
Symmetric multiprocessor (SMP) support
Native support for Symmetric Multiprocessors is one of NT’s key scalability features. SMP means that NT can scale as available hardware resources are increased, becoming instantly more efficient.
Scalable security model
Windows NT supports two different security models: the workgroup and domain models. Workgroups and domains provide very different levels of security (domains being the more secure), and together offer features to address the needs of small and large organizations alike. As a result, Windows NT can be used on networks as small as 2 computers or as large as 20,000 computers. The domain security model also offers several organizational submodels for organizations to choose from to manage users and resources across the enterprise.
SECURITY
Some of NT’s most important and touted features relate to security. Microsoft intended from the beginning for NT to be a secure operating system on which businesses and government could rely to protect their data. Windows NT’s security goes far beyond that of previous personal computer operating systems, providing security on par with that of many minicomputer and mainframe systems. To accomplish this, NT offers several layers of system security.
Domain security model
Windows NT’s domain security model is a sophisticated network access scheme that allows administrators to implement strict security regarding who receives access to what information and resources on the network. Special NT servers called domain controllers are responsible for authenticating user log on requests, and no user can gain access to network resources without first being authenticated by a domain controller. Security information on an NT system is stored in a special security database known as the SAM (Security Account Manager) database, which is continually replicated between all NT servers acting as domain controllers.
NTFS file system
Windows NT includes a special file system, NTFS, which complements NT’s security design. NTFS is tightly integrated with NT’s other security features, allowing administrators to utilize a variety of different access levels for users and users groups, down to the directory and file level. File level permissions means that individual files on NTFS volumes may be set with unique permissions, even different files residing in the same directory (folder).
Discretionary access control
Windows NT allows administrators and owners of system objects to have complete control over who gets what kinds of access to those objects (for example, a file or a printer). This type of security is known as discretionary access control, where the owner of a resource has discretion over who may access the resource and how. This level of security gives resource owners and system administrators an enormous amount of flexibility in controlling access to their data and resources.
Government C2 certification
Windows NT is a class C2-certified operating system. C2 is a strict government standard that defines the specific security features that must be present for use in U.S. government installations. These features must be met by any system wishing to obtain C2 status, and the system must pass a long and arduous testing process conducted by the government.
AUDIT TRAILS
Windows NT allows for the tracking of many system events, including all security-related events that occur on a system. This process is known as auditing. These events are recorded in a log file, which may be examined by the system administrator. Auditing can reveal break-in attempts and other attempted security breaches and provides administrators a good record of who has accessed the system and how.
Ctrl-Alt-Del login feature
Part of NT’s security is a feature designed to break “password grabbing” programs. These types of programs present a fake login screen to a user in hopes of capturing their username and password (for later use by some unauthorized party). In Windows NT, a user must press the Ctrl-Alt-Del keys before NT will present the login screen and allow the user to enter their name and password. You may know this key sequence as a system reboot or program shutdown command under MS-DOS and Windows 3.x/95, but in Windows NT, Ctrl-Alt-Del is used to “wake up” the Windows NT login manager and guarantees that the NT login screen is genuine and not a password-capture program. This works because software cannot be written to capture and process the Ctrl-Alt-Del keyboard sequence.
IS NT SELF–OPTIMIZING?
Microsoft touts Windows NT as a “highly self-optimizing” operating system. This is because NT offers self-optimization features that go well beyond all previous personal computer operating systems. With many operating systems, the ability to tune system performance requires arcane knowledge of special system startup files, settings, and system utilities. Under these operating systems (such as DOS and Windows 3.x), system performance depends heavily on these settings and can suffer greatly when they are improperly configured. One of Microsoft’s design goals for Windows NT was to remove this dependence on user settings and create an operating system that automatically provides most users with a decent level of performance.
NT’s self-optimizing features include the ability to dynamically allocate disk cache memory based on the available RAM in the system, dynamically modify the virtual memory/disk paging file to accommodate additional memory needs, and adjust application thread priorities as needed during operation. Don’t be fooled into thinking that all of NT’s performance-related settings are dynamically managed, however. It’s important to understand that most of NT’s performance-related settings were chosen by NT’s designers as “median” values, ones that would provide the best average performance across a variety of systems, but which may or may not produce the optimal settings for your specific environment. To ensure you are getting the most from your system, it is important to understand these settings and how changing them will affect your system’s operation.
Although NT’s self-optimization features are impressive, this does not mean that additional optimization of NT is impossible. Actually, there’s an inherent problem with this entire “self-optimizing” concept: it’s virtually impossible to create one all-encompassing implementation of NT that will provide maximum performance for everyone. The problem is that computers play many different roles within an organization, including file server, database server, Internet/intranet server, user workstation, CAD system. In addition, some computers play more than one of these roles simultaneously. How then, do we tell NT exactly how our machine is being used, what applications it’s running, and how to adjust itself to optimize performance?
Currently, Windows NT offers only a few basic configuration settings to define a computer’s role and usage. In a perfect world, you would rank system functions in a “1-to-10” fashion in order of importance to help NT properly allocate its resources and optimize performance (or better yet, have it automatically figure this out based on the applications currently running). However, since no such “optimization scorecard” exists, the best you can do to obtain the best performance for your system is use the tips offered in this book in conjunction with some manual configuration. We also show you how to use Performance Monitor, an extremely powerful tool included with every copy of Windows NT, to identify system performance bottlenecks.
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