Datasheet

4
CHAPTER 1 WINDOWS SERVER 2008 ARCHITECTURE
Figure 1.2
The heritage of the
Windows operating
system architecture
is evident in this
diagram of
Windows 2000/XP.
The kernel mode contains several major subsystems that are fundamental to its operation.
The Hardware Abstraction Layer (HAL) is software that is specifically compiled for the hardware
platform that Windows runs on, and is designed to make the operating system portable. When
Windows is ported to a different type of computer, the HAL can be recompiled for that platform’s
instruction set. The HAL thus preserves the code, command set, and APIs of the remaining kernel
mode components. The HAL’s hardware code controls I/O interfaces, interrupts, and processor
access.
The microkernel contains a minimal operating system: upon startup, it loads essential services
for address space management, thread management services, and Inter-Process Communication
(IPC). IPC is a set of methods for exchanging data between threads in one or more processes. In an
operating system with a true microkernel, the size of that microkernel is very small. Real-time operating
systems (RTOSs) that are used in embedded systems, such as vending machines or in cars, contain a
microkernel. The Windows operating system is more appropriately referred to as a hybrid kernel.
Executive Services communicate with the user mode subsystems, converting program com-
mands into object code in the Object Manager. Executive Services is where you find low-level secu-
rity routines, interface and process management, graphics display routines, power management,
and other vital services that make Windows Windows. These subsystems are organized into a set
Win32
Application
POSIX
Application
OS/2
Application
Work-
station
Service
Server
Service
Security
Integral Subsystems
Win32 POSIX OS/2
Environment Subsystems
User Mode
Hardware Abstraction Layer (HAL)
Hardware
Executive
Executive Services
Object Manager
I/O
Manager
Security
Reference
Monitor
IPC
Manager
Virtual
Memory
Manager
(VMM)
Process
Manager
PnP
Manager
Power
Manager
Window
Manager
GDI
Kernel Mode Drivers Microkernel
Kernel Mode
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