Mumbai University > COMPS > Sem 5 > Operating System

Marks: 10 M

Year: Dec 2014

System components in Windows Operating System

The architecture of Windows XP is a layered system of modules, as shown in Fig below. The main layers are the HAL, the kernel, and the executive, all of which run in protected mode, and a collection of subsystems and services that run in user mode.

The user-mode subsystems fall into two categories:

1. The environmental subsystems, which emulate different operating systems,
2. The protection subsystems, which provide security functions.

These layers and subsystems are described below:

1. Hardware-Abstraction Layer:

The HAL is the layer of software that hides hardware differences from upper levels of the operating system, to help make Windows XP portable.

1. Kernel:

The kernel of Windows XP has four main responsibilities: thread scheduling, interrupt and exception handling, low-level processor synchronization, and recovery after a power failure.

1. Executive:

The Windows XP executive provides a set of services that all environmental subsystems use. The services are grouped as follows:

3.1 Object manager

For managing kernel-mode entities, Windows XP uses a generic set of interfaces that are manipulated by user-mode programs. Windows XP calls these entities objects, and the executive component that manipulates them is the Object Manager

3.2 Virtual memory manager

The executive component that manages the virtual address space, physical memory allocation, and paging is the Virtual memory manager.

3.3 Process manager

The Windows XP process manager provides services for creating, deleting, and using processes, threads, and jobs.

3.4 Local procedure call facility

The implementation of Windows XP uses a client-server model. The client-server model is used for implementing a variety of operating-system services besides the environmental subsystems. Security management, printer spooling, Web services, network file systems, plug-and play, and many other features are implemented using this model.

3.5 I/O manager

The I/O manager is responsible for file systems, device drivers, and network drivers. It keeps track of which device drivers, filter drivers, and file systems are loaded, and it also manages buffers for I/O requests

3.6 Cache manager

The cache manager works closely with the VM manager to provide cache services for all components under the control of the I/0 manager. Caching in Windows XP is based on files rather than raw blocks.

3.7 Security reference monitor

The Security reference monitor (SRM) checks the process's security token and the object's access-control list to see whether the process has the necessary rights.

3.8 Plug-and-play and power managers

The Plug-and-Play (PnP) manager automatically recognizes installed devices and detects changes in devices as the 22.3 873 system operates.

3.9 Registry

Windows XP keeps much of its configuration information in an internal database called registry. A registry database is called a hive. There are separate hives for system information, default user preferences, software installation, and security

3.10 Booting

The booting of a Windows XP PC begins when the hardware powers on and the BIOS begins executing from ROM. The BIOS identifies the to be booted and loads and executes the bootstrap loader from the front of the disk.