Windows 2000 is a continuation of the Microsoft Windows NT line of operating systems, replacing its predecessor, Windows NT 4.0. Originally called Windows NT 5.0, then Windows NT 2000, Microsoft changed the name to Windows 2000 on October 27, 1998. It was also the first Windows version that was released without a code name, though Windows 2000 Service Pack 1 was codenamed "Asteroid" and Windows 2000 64-bit was codenamed "Janus" (not to be confused with Windows 3.1, which had the same codename). The first beta for Windows 2000 was released on September 27, 1997 and several further betas were released until Beta 3 which was released on April 29, 1999 DEC Alpha support was removed from the final build. From here, Microsoft issued three release candidates between July and November 1999, and finally released the operating system to partners on December 12, 1999The public received the full version of Windows 2000 on February 17, 2000. Three days before the launch of Windows 2000, which Microsoft advertised as "a standard in reliability", a leaked memo from Microsoft reported on by Mary Jo Foley revealed that Windows 2000 had "over 63,000 potential known defects".After Foley's article was published, Microsoft blacklisted her for a considerable time: InformationWeek summarized the release "our tests show the successor to NT 4.0 is everything we hoped it would be. Of course, it isn't perfect either."Wired News later described the results of the February launch as "lackluster". Novellcriticized Microsoft's Active Directory, the new directory service architecture to be less scalable or reliable than their own Novell Directory Services (NDS) technology.
Originally, Windows 2000 was planned to replace both Windows 98 and Windows NT 4.0. However, that was later changed. Instead, an updated version of Windows 98 called Windows 98 Second Edition was released in 1999 as a successor to Windows 98. Microsoft released Windows 2000 Datacenter Server, targeted at large-scale computing systems with support for 32 processors, on September 29, 2000.
On or shortly before February 12, 2004, "portions of the Microsoft Windows 2000 and Windows NT 4.0 source code were illegally made available on the Internet". The source of the leak remains unannounced. Microsoft issued the following statement:
“
Microsoft source code is both copyrighted and protected as a trade secret. As such, it is illegal to post it, make it available to others, download it or use it.
”
Despite the warnings, the archive containing the leaked code spread widely on the file-sharing networks. Consequentially, on February 16, 2004, an exploit "allegedly discovered by an individual studying the leaked source code" for certain versions of Microsoft Internet Explorer was reported.
Windows 2000 is a highly modular system that consists of two main layers: a user mode and a kernel mode. The user mode refers to the mode in which user programs are run. Such programs are limited in terms of what system resources they have access to, while the kernel mode has unrestricted access to the system memory and external devices. All user mode applications access system resources through the executive which runs in kernel mode.
User mode
User mode in Windows 2000 is made of subsystems capable of passing I/O requests to the appropriate kernel mode drivers by using the I/O manager. Two subsystems make up the user mode layer of Windows 2000: the environment subsystem and the integral subsystem.
The environment subsystem was designed to run applications written for many different types of operating systems. These applications, however, run at a lower priority than kernel mode processes. There are three main environment subsystems:
Win32 subsystem runs 32-bit Windows applications and also supports Virtual DOS Machines (VDMs) , which allows MS-DOS and 16-bit Windows 3.1x (Win16) applications to run on Windows.
OS/2 environment subsystem supports 16-bit character-based OS/2 applications and emulates OS/2 1.3 and 1.x, but not 32-bit or graphical OS/2 applications as used on OS/2 2.x or later.
POSIX environment subsystem supports applications that are strictly written to either the POSIX.1 standard or the related ISO/IEC standards.
The integral subsystem looks after operating system specific functions on behalf of the environment subsystem. It consists of a security subsystem (grants/denies access and handles logons) , workstation service (helps the computer gain network access) and a server service (lets the computer provide network services).
Kernel mode
Kernel modein Windows 2000 has full access to the hardware and system resources of the computer. The kernel mode stops user mode services and applications from accessing critical areas of the operating system that they should not have access to.
Each object in Windows 2000 exists in its own namespace, as illustrated by this screenshot from SysInternal's WinObj
The executive interfaces with all the user mode subsystems. It deals with I/O, object management, security and process management. It contains various components, including:
Object manager: a special executive subsystem that all other executive subsystems must pass through to gain access to Windows 2000 resources. This is essentially a resource management infrastructure service that allows Windows 2000 to be an object oriented operating system.
I/O Manager: allows devices to communicate with user-mode subsystems by translating user-mode read and write commands and passing them to device drivers.
Security Reference Monitor (SRM) : the primary authority for enforcing the security rules of the security integral subsystem.
IPC Manager: short for Inter-Process CommunicationManager, manages the communication between clients (the environment subsystem) and servers (components of the executive).
Virtual Memory Manager: manages virtual memory, allowing Windows 2000 to use the hard disk as a primary storage device (although strictly speaking it is secondary storage).
Process Manager: handles process and thread creation and termination
PnP Manager: handles Plug and Play and supports device detection and installation at boot time.
Power Manager: the power manager coordinates power events and generates power IRPs.
The display system is handled by a device driver contained in Win32k.sys. The Window Manager component of this driver is responsible for drawing windows and menus while the GDI (Graphics Device Interface) component is responsible for tasks such as drawing lines and curves rendering fonts and handling palettes. Windows 2000 also introduced alpha blending into the Graphics Device Interface which reflects in the fade effect in menus.
The Windows 2000 Hardware Abstraction Layer, or HAL, is a layer between the physical hardware of the computer and the rest of the operating system. It was designed to hide differences in hardware and therefore provide a consistent platform to run applications on. The HAL includes hardware specific code that controls I/O interfaces, interrupt controllersand multiple processors.
The hybrid kernel sits between the HAL and the executive and provides multiprocessor synchronization, thread and interrupt scheduling and dispatching, trap handling and exception dispatching. The hybrid kernel often interfaces with the process manager and is responsible for initializing device drivers at bootup that are necessary to get the operating system up and running.
A stripped down variant of the Windows
Originally, Windows 2000 was planned to replace both Windows 98 and Windows NT 4.0. However, that was later changed. Instead, an updated version of Windows 98 called Windows 98 Second Edition was released in 1999 as a successor to Windows 98. Microsoft released Windows 2000 Datacenter Server, targeted at large-scale computing systems with support for 32 processors, on September 29, 2000.
On or shortly before February 12, 2004, "portions of the Microsoft Windows 2000 and Windows NT 4.0 source code were illegally made available on the Internet". The source of the leak remains unannounced. Microsoft issued the following statement:
“
Microsoft source code is both copyrighted and protected as a trade secret. As such, it is illegal to post it, make it available to others, download it or use it.
”
Despite the warnings, the archive containing the leaked code spread widely on the file-sharing networks. Consequentially, on February 16, 2004, an exploit "allegedly discovered by an individual studying the leaked source code" for certain versions of Microsoft Internet Explorer was reported.
Windows 2000 is a highly modular system that consists of two main layers: a user mode and a kernel mode. The user mode refers to the mode in which user programs are run. Such programs are limited in terms of what system resources they have access to, while the kernel mode has unrestricted access to the system memory and external devices. All user mode applications access system resources through the executive which runs in kernel mode.
User mode
User mode in Windows 2000 is made of subsystems capable of passing I/O requests to the appropriate kernel mode drivers by using the I/O manager. Two subsystems make up the user mode layer of Windows 2000: the environment subsystem and the integral subsystem.
The environment subsystem was designed to run applications written for many different types of operating systems. These applications, however, run at a lower priority than kernel mode processes. There are three main environment subsystems:
Win32 subsystem runs 32-bit Windows applications and also supports Virtual DOS Machines (VDMs) , which allows MS-DOS and 16-bit Windows 3.1x (Win16) applications to run on Windows.
OS/2 environment subsystem supports 16-bit character-based OS/2 applications and emulates OS/2 1.3 and 1.x, but not 32-bit or graphical OS/2 applications as used on OS/2 2.x or later.
POSIX environment subsystem supports applications that are strictly written to either the POSIX.1 standard or the related ISO/IEC standards.
The integral subsystem looks after operating system specific functions on behalf of the environment subsystem. It consists of a security subsystem (grants/denies access and handles logons) , workstation service (helps the computer gain network access) and a server service (lets the computer provide network services).
Kernel mode
Kernel modein Windows 2000 has full access to the hardware and system resources of the computer. The kernel mode stops user mode services and applications from accessing critical areas of the operating system that they should not have access to.
Each object in Windows 2000 exists in its own namespace, as illustrated by this screenshot from SysInternal's WinObj
The executive interfaces with all the user mode subsystems. It deals with I/O, object management, security and process management. It contains various components, including:
Object manager: a special executive subsystem that all other executive subsystems must pass through to gain access to Windows 2000 resources. This is essentially a resource management infrastructure service that allows Windows 2000 to be an object oriented operating system.
I/O Manager: allows devices to communicate with user-mode subsystems by translating user-mode read and write commands and passing them to device drivers.
Security Reference Monitor (SRM) : the primary authority for enforcing the security rules of the security integral subsystem.
IPC Manager: short for Inter-Process CommunicationManager, manages the communication between clients (the environment subsystem) and servers (components of the executive).
Virtual Memory Manager: manages virtual memory, allowing Windows 2000 to use the hard disk as a primary storage device (although strictly speaking it is secondary storage).
Process Manager: handles process and thread creation and termination
PnP Manager: handles Plug and Play and supports device detection and installation at boot time.
Power Manager: the power manager coordinates power events and generates power IRPs.
The display system is handled by a device driver contained in Win32k.sys. The Window Manager component of this driver is responsible for drawing windows and menus while the GDI (Graphics Device Interface) component is responsible for tasks such as drawing lines and curves rendering fonts and handling palettes. Windows 2000 also introduced alpha blending into the Graphics Device Interface which reflects in the fade effect in menus.
The Windows 2000 Hardware Abstraction Layer, or HAL, is a layer between the physical hardware of the computer and the rest of the operating system. It was designed to hide differences in hardware and therefore provide a consistent platform to run applications on. The HAL includes hardware specific code that controls I/O interfaces, interrupt controllersand multiple processors.
The hybrid kernel sits between the HAL and the executive and provides multiprocessor synchronization, thread and interrupt scheduling and dispatching, trap handling and exception dispatching. The hybrid kernel often interfaces with the process manager and is responsible for initializing device drivers at bootup that are necessary to get the operating system up and running.
A stripped down variant of the Windows
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