Windows XP Structure

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Operating system:

It is a program that runs on a computer. It manages the computer hardware and also provides the basis for application program.

A few operating systems are gven below

Windows Xp

Mac OS

Windows CE




The Kernel fully accesses the system's Memory and allows the processes to safely access the memory as they require it. For accessing the memory kernel uses

· Paging and/or Segmentation

· Virtual Addressing:

Allows the kernel to make given physical address to be virtual address.
At a particular address the virtual memory for the different processes may be different, allowing every program to behave as if it is the only one running and prevents the applications from crashing.

Provides Layer of indirection means referring to the data which is not currently in the memory, it allows the OS to use other data stores like hard drive that allows the OS to use more memory than the system has physically available.

Provides Demand Paging:

For the data which is not in the main memory CPU signals kernel, it responds by writing the contents of inactive memory block to the disk and replacing it with data requested by program.

Allows creation of Virtual Partitions of memory in two disjointed areas kernel (kernel space) and applications (user space).

Prevents an application from damaging the running kernel as applications can not address kernel memory.

Ø Windows XP improvements

· Paged pool Limit of 470 has been lifted from Memory Manage in XP.

· Data structures allocated for parts of file that have active views with unmapped views reusable by memory manager depending on pool usage.

· XP supports larger virtual address space (1.3 GB, of which the contiguous virtual address space that can be used by device drivers is 960 MB).

· The registry reimplemented outside the paged pool; the registry hives are memory mapped by the Cache Manager into the system cache, eliminating the registry size limit.

· The Configuration Manager has been updated to minimize the registry's memory footprint and lock contention, reduce fragmentation and speed up query processing

· Kernel page write protection limit is enabled on the systems up to 256 MB of RAM enabling large pages.

· Reduced Lock contention

· Unnecessary locks used in resource synchronizations (RAM allocation and mapping through Address Windowing, Extension, system page table entries, charging non paged /paged pool quotas, charging commitment of pages) have been removed.

· Reduced Dispatcher lock contention

· Optimized Page Frame Number (PFN) for increased parallelism and granularity.

· XP uses push locks if there is no contention as they support shared and exclusive acquisition. Push locks are used to protect handles table entries, the Object Manager (to protect data structures and security descriptors) and Memory Manager (to protect AWE-related locks).

· Windows XP uses the SYSENTER/SYSEXIT mechanisms which require fewer clock cycles to transition to and from user mode to kernel mode to speed up system calls.

· Windows XP includes simultaneous multithreading support. Simultaneous multithreading is a processor's ability to process more than one data thread at a time.

· The Windows XP kernel is completely different from the kernel of the Windows 9x/Me line of operating systems.

Mac OS

* Series of Graphical user interface developed by Apple.

* Early System Software was held in ROM with updates on floppy disk provided by Apple Dealers.

* Early versions of the Mac OS were compatible only with Motorola 68000-based Macintoshes.

* Initially consisted of two pieces of Software called System and Finder.

* Divided into two Families:1)Mac OS classic Family

2)Mac OS X operating System.

Ø The Kernel

The Kernel of Mac OS is called XNU

§ XNU's Mach is responsible for various low-level aspects of the system, such as: preemptive multitasking, including kernel threads (POSIX threads on Mac OS X are implemented using kernel threads)

§ protected memory

§ virtual memory management

§ inter-process communication

§ interrupt management

§ real-time support

§ kernel debugging support (the built-in low-level kernel debugger, ddb, is part of XNU's Mach component, and so is kdp, a remote kernel debugging protocol implementation)

§ console I/O

Ø Features

* The 'minor' Mac OS upgrade's treasure trove of new features

* ExposeA© meets the Dock

* The Dock's new look

* Wi-Fi status always available

* The right time wherever you are

* Easy flight status checking

* Recover your trash - again

* System preferences: New, changed, and gone

* Trackpad gestures for all

* Bluetooth setup is now in context

* Services are now contextual

* My scanner is your scanner

* Quicker Sidebar customization

* Preview comes closer to Adobe Reader

* QuickTime Pro is now free

* Your top sites in Safari

* New aurora, slider-sized Finder icons


§ UNIX-based operating system introduced by Sun Microsystems in 1992 as the successor to SunOS.

§ Known for its scalability, especially on SPARC systems, and for originating many innovative features such as DTrace and ZFS

§ SPARC-based and x86-based workstations and servers from Sun and other vendors, with efforts underway to port to additional platforms.

Ø Features

§ Security

§ Observability

§ Performance

§ Performance

§ Networking

§ Virtualization

§ Data Management

§ Availability

§ Dynamic Tracing (DTrace) - real time debugging and performance troubleshooting

§ Virtualization (Sun Containers) - container cloning and migration

§ Logical Domains - up to 32 with dynamic resource allocation

§ Certified Multi-Level Security (Solaris Trusted Extensions)

§ Predictive Self-Healing - fine grained recovery

§ ZFS File System - 64-bit checksums, pooled storage, 128-bit file system

§ Interoperability

§ Networking

§ Platform choice

Windows CE

Ø The Kernel

Microsoft Windows CE devices send, receive and process information that requires protection from potentially unsafe applications. To help protect your device, you can implement security measures that can help prevent the OS from loading unknown modules, restrict access to system application programming interfaces (APIs), and prevent write access to parts of the system registry

The kernel can use this information to prevent unauthorized applications from loading or limit their access to the system.

Implement following following functions to create trusted environment.

* OEMCertifyModuleInit

* OEMCertifyModule

Before the kernel loads an application, the OEMCertifyModule function verifies the application signature to help protect your system from unfamiliar applications.

Ø Role of Kernel

* The Microsoft® Windows® CE kernel, which is represented by the Coredll module, is the core of the Windows CE operating system (OS).

* The kernel provides the base OS functionality for any Windows CE device. This functionality includes process, thread, and memory management.

* The kernel also provides some file-management functionality. The kernel services enable applications to use this core functionality.

* The Windows CE kernel uses a paged virtual memory system to manage and allocate program memory

Ø Features

§ Connectivity
§ Pocket Excel
§ Pocket Outlook
§ Pocket PowerPoint
§ Pocket Word
§ Printing
§ Programming Languages
§ System
§ AutoHotkey
§ Development tools

§ Windows CE Error Report


* Microsoft Windows CE 2.0 for the Handheld PC

* Microsoft Pocket Excel 2.0

* Microsoft Pocket Outlook 2.0

* Microsoft Pocket PowerPoint 1.0

* Microsoft Pocket Word 2.0


· Initially developed by Linux Torvalds in 1991 as an operating system for IBM-compatible personal computers based on the Intel 80386 microprocessor

Ø The Kernel

· The Linux kernel has the ability to load and unload arbitrary sections of kernel code on demand.

· “Kernel modules allow a Linux system to be set up with a standard, minimal kernel, without any extra device drivers built in.”.

· The module support under Linux has three components:

1. The module management allows modules to be loaded into memory and to talk to the rest of the kernel.

2. The driver registration allows modules to tell the rest of the kernel that a new driver has become available.

3. A conflict-resolution mechanism allows different device drivers to reserve hardware resources and to protect those resources from accidental use by another driver.

Ø Kernel Functions

* Process Management

* Symmetric Multiprocessing

* Kernel synchronization

* Segmentation /Paging in Linux

* Regular Paging


* Jesse D. Kornblum (No Date) “The Linux Kernel and the Forensic Acquisition of Hard Disks with an Odd Number of Sectors” International Journal of Digital Evidence, Fall 2004, Volume 3, Issue 2 Availbale at: http//:

* Robert Love(Apr 15, 2005) “Linux kernel process management” Available at:Li






Windows XP Memory Management

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