Windows NT

Windows NT (New Technology) is an operating system family, released by Microsoft corporation from the middle of 1993. Were originally positioned as systems for workstations and servers.

History Windows NT

At the end of the 88th year of Microsoft charged to David Cutler to head the new project in the field of the software: create the new operating system of Microsoft corporation for the 1990th years. He gathered a team of engineers for development of the system of new technology (New Technology - NT).

It was originally going to develop NT with user and program (API) interfaces in OS/2 style, however OS/2 badly was on sale, and Windows 3.0 made great and permanent success in the market. Having seen the market reference points and difficulties connected with development and support of two incompatible systems, Microsoft decided to change the course and to direct the engineers towards the strategy of the single integral operating system. This strategy of a sostyal is in developing family of the operating systems which are based on Windows which would cover a set of types of computers, from the smallest notebooks to the biggest multiprocessor workstations. So, the next generation of Windows systems was called by Windows NT.

Windows NT supports the graphical interface (GUI) Windows and also is the first operating system of Microsoft company supporting Win32 API, the 32-bit program interface for development of new applications which is based on Windows. Win32 API makes available to applications the improved properties of the operating system, such as mnogonitevy processes, synchronization, security, I/O, object management.

In July, 1993 the first operating systems of the NT family - Windows NT 3.1 and Windows NT Advanced Server 3.1 appeared.

Versions

• Windows NT 3.1 (on July 27, 1993)
• Windows NT 3.5 (on September 21, 1994)
• Windows NT 3.51 (on May 30, 1995)
• Windows NT 4.0 (on August 24, 1996)
• Windows 2000 (on February 17, 2000)
• Windows XP (on October 25, 2001)
• Windows XP 64-bit Edition (on March 28, 2003)
• Windows Server 2003 (on April 25, 2003)
• Windows XP Media Center Edition 2003 (on December 18, 2003)
• Windows XP Media Center Edition 2005 (on October 12, 2004)
• Windows XP Professional x64 Edition (on April 25, 2005)
• Windows Fundamentals for Legacy PCs (8 июля 2006 г.)
• Windows Vista (on November 30, 2006)
• Windows Home Server (on November 7, 2007)
• Windows Server 2008 (on February 27, 2008)
• Windows 7
• Windows 8
• Windows 8.1

Structure of Windows NT

Structurally Windows NT can be presented in the form of two parts: the part of the operating system working in the user's mode and the part of the operating system working in a kernel mode

The part of Windows NT working in a kernel mode is called an execution part (executive). She turns on a number of components which manage a virtual memory, objects (resources), input-output and the file system (including network drivers), interaction of processes and partially a security system. These components interact among themselves with the help of intermodular communication. Each component causes others using a set of carefully specified internal procedures.

The second part of Windows NT working in the user's mode is made by servers - the so-called protected subsystems. As subsystems cannot automatically share memory, they communicate with each other by means of sending of messages. Messages can be transferred both between the client and the server, and between two servers. All messages pass through an execution part of Windows NT. The kernel of Windows NT plans threads of the protected subsystems in the same way as threads of normal applied processes.

Support of the protected subsystems is provided by an execution part. Its components are:

• Manager of objects. Creates, deletes and manages objects of an execution part - abstract data types, the system resources used for representation.
• Security reference monitor. Sets rules of protection on the local computer. Protects resources of the operating system, executes protection and registration of the performed objects.
• Manager of processes. Creates and completes, stops and resumes processes and threads and also stores about them information.

Manager of a virtual memory.

• Input-output subsystem. Includes the following components:
  • the manager of input-output providing means of input-output, device-independent;
  • file systems are the NT drivers executing the file - the focused requests for input-output and broadcasting them in calls of normal devices;
  • a network redirector and the network server - the drivers of file systems transferring remote queries for input-output for machines of network and receiving requests from them;
  • drivers of devices of an execution part are low-level drivers which directly manage the device;
  • the manager of a cache implementing disk caching.

The execution part, in turn, is based on the services of the bottom level provided by a core of NT. As a core enters:

• planning of processes,
• interrupt handling and exclusive situations,
• synchronization of processors for multiple processor systems,
• system recovery after failures.

The core works in a kernel mode and is never removed from memory. It is possible to address a core only by means of interruption.

The protected subsystems of Windows NT work in a user mode and are created by Windows NT in load time of the operating system. Right after creation they begin an infinite loop of the accomplishment, responding to the messages arriving to them from applied processes and other subsystems. Among the protected subsystems it is possible to select the subclass called by environment subsystems. Subsystems of an environment implement interfaces of applicationss of the operating system (API). Other types of subsystems called by integrated subsystems perform tasks necessary for the operating system. For example, the most part of a security system of Windows NT is implemented in the form of an integrated subsystem, network servers are also executed as integrated subsystems.

The most important subsystem of an environment is Win32 - a subsystem which provides access for applications to 32-bit to Windows API. In addition this system provides the graphical interface and manages input-output of data of the user.

Each protected subsystem works in the user's mode, calling system service of an execution part for accomplishment of exclusive actions in a kernel mode. Network servers can be executed both in regime of the user, and in a kernel mode, how they are developed.

Subsystems communicate among themselves by transmission of messages. When, for example, the user application causes some API procedure, the environment subsystem providing this procedure receives the message and executes it or addressing a core, or sending the message to other subsystem. After completion of the procedure the subsystem of an environment sends to the application the message containing a returned value. Sending of messages and other activity of the protected subsystems is invisible to the user.

The fixed asset fastening all subsystems of Windows NT in a whole is the mechanism of a call of local procedures (Local Procedure Call - LPC). LPC represents the optimized option of more general means - a remote call of procedures (RPC) which is used for communication of the clients and servers located by different machines of network.

Means of LPC support several methods of data transmission between clients and servers: one is usually used for transfer of short messages, another - for long messages, and the third is optimized especially for use by Win32 subsystem. Each subsystem sets port - a communication channel by means of which other processes can contact it. Ports are implemented as objects.

See Also

• Microsoft Windows
• Microsoft corporation

Links

• Network operating systems N.A. Olifer, V.G. Olifer
• Microsoft Windows history