Windows 2000

 

32-bit preemptive multitasking operating system for Intel microprocessors.

Key goals for the system:

 

     1. portability

     2. security

     3. POSIX compliance

     4. multiprocessor support

     5. extensibility

     6. international support

     7. compatibility with MS-DOS and MS-Windows applications.

 

Uses a micro-kernel architecture.

 

Available in four versions, Professional, Server, Advanced Server, National Server.

In 1996, more NT server licenses were sold than UNIX licenses

 

History

 

In 1988, Microsoft decided to develop a “new technology” (NT) portable operating system that supported both the OS/2 and POSIX APIs.

 

Originally, NT was supposed to use the OS/2 API as its native environment but during development NT was changed to use the Win32 API, reflecting the popularity of Windows 3.0.

 

Design Principles

 

1.Extensibility — layered architecture.

  • Executive, which runs in protected mode, provides the basic system services.

  • On top of the executive, several server subsystems operate in user mode.

  • Modular structure allows additional environmental subsystems to be added without  affecting    the executive.

 

2.Portability — 2000 can be moved from on hardware architecture to another with relatively few changes.

  •  Written in C and C++.

  •   Processor-dependent code is isolated in a dynamic link  

library (DLL) called the “hardware abstraction layer” (HAL).

Silberschatz, Galvin and Gagne 2002 21.5 Operating System Concepts 

 

3.  Reliability — 2000 uses hardware protection for virtual memory, and software protection   

     mechanisms for operating system resources.

 

4.  Compatibility — applications that follow the IEEE 1003.1 (POSIX) standard can be complied 

       to run on 2000 without changing the source code.

 

5. Performance — 2000 subsystems can communicate with one another via high-performance

    message passing.

  •  Preemption of low priority threads enables the system to  respond quickly to external events.

  •  Designed for symmetrical multiprocessing.

6.  International support — supports different locales via the national language support

     (NLS) API.

 

2000 Architecture

 

 Layered system of modules.

 Protected mode — HAL, kernel, executive.

 User mode — collection of subsystems

 

   1.   Environmental subsystems emulate different operating systems.

   2.  Protection subsystems provide security functions.

  

Depiction of 2000 Architecture

 

          

 

 Foundation for the executive and the subsystems.

 Never paged out of memory; execution is never preempted.

 Four main responsibilities:

 

   1. thread scheduling

   2. interrupt and exception handling

   3. low-level processor synchronization

   4. recovery after a power failure

 

Kernel is object-oriented, uses two sets of objects.

   1. dispatcher objects control dispatching and synchronization (events, mutants, mutexes,   

       semaphores, threads and timers).

   2. control objects (asynchronous procedure calls, interrupts, power notify, power status, 

       process and profile objects.)

 

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