Page 308 - DCAP403_Operating System

Unit 14: Windows 2000

Windows 2000 (also referred to as Win2K) is a preemptive, interruptible, graphical and Notes
business-oriented operating system designed to work with either uni-processor or symmetric
multi-processor computers. It is part of the Microsoft Windows NT line of operating systems
and was released on February 17, 2000. It was succeeded by Windows XP in October 2001 and

Windows Server 2003 in April 2003. Windows 2000 is classified as a hybrid kernel operating
system. Key goals for the system are portability, security, Portable Operating System Interface
(POSIX) or IEEE Std. 1003.1 compliance, multiprocessor support, extensibility, international
support, and compatibility with MS-DOS and MS-Windows applications.
The Windows 2000 product line consists of four products:
1. Windows 2000 Professional: Supports up to two processors and up to 4GB of RAM. Used as
a workstation or client computer and it is the replacement for Windows NT Workstation.

2. Windows 2000 Server: Supports up to four processors and up to 4GB of RAM. It is used for
web, application, print and fi le servers.
3. Windows 2000 Advanced Server: Supports up to eight processors and up to 8GB of RAM.
It is used in an enterprise network and very useful as an SQL server.
4. Windows 2000 Datacenter Server: Supports up to 32 processors and up to 64GB of RAM.
It is used in an enterprise network to support extremely large databases and real time
processing.
In this unit, we discuss the key goals for this system, the layered architecture of the system that
makes it so easy to use, the file system, networks and the programming interface.

14.1 Design Principles

The design goals that Microsoft has stated for Windows 2000 include extensibility, portability,
reliability, compatibility, performance, and international support.
Extensibility refers to the capacity of an operating system to keep up with advancements in
computing technology. So that changes are facilitated over time, the developers implemented
Windows 2000 using a layered architecture.
The Windows 2000 executive, which runs in kernel or protected mode, provides the basic system
services. On top of the executive, several server subsystems operate in user mode. Among them
are environmental subsystems that emulate different operating systems. Thus, programs written
for MS-DOS, Microsoft Windows, and POSIX can all run on Windows 2000 in the appropriate
environment. Because of the modular structure, additional environmental subsystems can be
added without affecting the executive. In addition, Windows 2000 uses loadable drivers in the

I/O system, so new file systems, new kinds of I/O devices, and new kinds of networking can
be added while the system is running. Windows 2000 uses a client-server model like the Mach
operating system, and supports distributed processing by remote procedure calls (RPCs) as

defined by the Open Software Foundation.
An operating system is portable if it can be moved from one hardware architecture to another
with relatively few changes. Windows 2000 is designed to be portable. As is true of the UNIX
operating system, the majority of the system is written in C and C++. All processor-dependent
code is isolated in a dynamic link library (DLL), called the hardware-abstraction layer (HAL). A

DLL is a file that gets mapped into a process’s address space such that any functions in the DLL
appear as though they are part of the process. The upper layers of Windows 2000 depend on
HAL, rather than on the underlying hardware, and that helps Windows 2000 to be portable. HAL
manipulates hardware directly, isolating the rest of Windows 2000 from hardware differences
among the platforms on which it runs.

Reliability is the ability to handle error conditions, including the ability of the operating system to
protect itself and its users from defective or malicious software. Windows 2000 resists defects and

LOVELY PROFESSIONAL UNIVERSITY 301