Operating Systems And Microsoft Windows Computer Science

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MS WINDOWS is a series of software OS and graphical user interfaces which is produced by MICROSOFT. The term WINDOWS, in all describes any or all of the generations of MICROSOFT OS products. The early versions of WINDOWS were often as a simple GUI because it ran over MS-Dos and used it for file system services. However even then WINDOWS versions already assumed many costumed OS functions such as having their own executable file format and their own device drivers for timer, graphics, printer, mouse, keyboard and sound .The first ever operating system of windows by Microsoft was produced in 1985 as an add-on to MS_DOS and in response to the fuming interest in a better user interfaces (GUIs). Microsoft Windows totally dominated and still is doing as the world's most used OS in personal and industrial computer market, overtaking the MAC OS, which had been introduced previously. According to a research conducted in October 2009, Windows had approximately 91% of the market share of the client operating systems for usage on the Internet. The most recent client version of Windows is WINDOWS 7; the most recent server version is WINDOWS Server 08 R2 and the most recent mobile device version is WINDOWS Mobile 6.5.

Microsoft has always maintained two parallel routes in OS. One has been for home users which has greater, larger and better multimedia support and less functionality in Networking and Security. The other has been for the professional IT users which Networking and Security. The history of Windows dates back to September 1981, when a project named "Interface Manager" was started by MICROSOFT but it was announced in November 1983, after Apple had come up with their LISA, under the name "Windows".


WINDOWS 1.0 was not released until November 1985. The root of Windows 1.0 was a program known as the MS-DOS Executive. The other supplied features were Calculator, Calendar, Clipboard viewer, Clock, Control panel, Notepad and Paint but Windows 1.0 did not allow overlapping windows. Instead all windows were tiled only dialog boxes could appear over other windows.

WINDOWS 2.0 was released in October 1987 and featured several improvements to the user interface and memory management. Windows 2.0 allowed application windows to overlap each other and also introduced more sophisticated keyboard-shortcuts.

WINDOWS 2.1 was released in two different flavors: WINDOWS 386 and WINDOWS 286, both having features of their own. Windows implemented an elaborate, segment-based, software virtual memory scheme, which allowed it to run applications larger than available memory: code segments resources were swapped in and thrown away when memory became scarce, and data segments moved in memory when a given application had relinquished processor control, typically waiting for user input.

WINDOWS 3.0(released in1990) and WINDOWS 3.1( released in1992) improved the design, mostly because of the implementation of  Virtual memory concept and loadable virtual device drivers which allowed them to share arbitrary devices between multitasked DOS windows Also, Windows applications could now run in protected mode, which gave them access to several megabytes of memory and removed the obligation to participate in the software virtual memory scheme. They still ran inside the same address space, where the segmented memory provided a degree of protection, and multi-tasked cooperatively. For Windows 3.0, Microsoft also rewrote critical operations from C language to Assembly language, making this release faster and less memory-hungry than its predecessors.  With the introduction of the WINDOWS for Workgroup 3.11, Windows was able to bypass DOS for file management operations using 32 bit file access.

In July 1993, Microsoft released WINDOWS NT based on a new kernel. NT was considered to be the professional OS and was the first Windows version to utilize multitasking. Windows NT would later be reused to also function as a home operating system, with Windows XP.

On August 24, 1995, Microsoft released WINDOWS 95 a new, and major, consumer version that made further changes to the user interface. Windows 95 was designed to replace not only Windows 3.1, but also Windows for Workgroups, and MS-DOS. It was also the first Windows operating system to use Plug and Play capabilities. The changes Windows 95 brought to the desktop were revolutionary.

The next in the consumer line was Microsoft WINDOWS 98 released on June 25, 1998. It was substantially criticized for its slowness and for its unreliability compared to WINDOWS 95 but many of its basic problems were later rectified with the release of WINDOWS 98 Second Edition in 1999. 

As part of its "professional" line, Microsoft released WINDOWS 2000 in February 2000. The consumer version following Windows 98 was WINDOWS ME, which stands for Windows Millennium Edition. Released in September 2000, WINDOWS ME implemented a number of new technologies for Microsoft: most notably publicized was "UNIVERSAL PLUG AND PLAY".

In October 2001, Microsoft released WINDOWS XP, a version built on the Windows NT Kernel that also retained the consumer-oriented usability of Windows 95 and its successors. This new version was widely praised. It was further released in two distinct editions, "Home" and "Professional", the former lacking many of the superior security and networking features of the Professional edition. Additionally, the first "Media Center" edition was released in 2002, with an emphasis on support for DVD and TV functionality including program recording and a remote control.

In April 2003, WINDOWS Server 2003 was introduced, which replaced the WINDOWS 2000 line of server products with a number of new features and a strong focus on security; this was followed in December 2005 by Windows Server 2003 R2.

On January 30, 2007 Microsoft released WINDOWS VISTA, which contained a number of new features from a redesigned shell and user interface to significant technical changes, with a particular focus on Security features.


LINUX is a generic term referring to UNIX-like computer Operating systems which is based on its kernel called as the Linux kernel. The name LINUX comes from the LINUX kernel, originally written by Linus Torvalds. Since the initial release of the source code in the year 1991, the LINUX has grown from a small number of C language files to a 370 MB of source files under a standard license. The LINUX development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed, both commercially and non-commercially, by anyone under licenses such as the GNU (GENERAL PUBLIC LISCENCE).

The primary difference between Linux and many other popular contemporary operating systems is that the LINUX kernel and other components are free and open source software. Linux is not the only such operating system, although it is by far the most widely used. 

Typically Linux is packaged in a format known as a LINUX distribution for desktop and server use. Linux distributions include the Linux kernel and all of the supporting software required to run a complete system, such as utilities and libraries, the Windows System, desktop environment and the Apache HTTP Server. The most commonly-used applications with desktop Linux systems include the Mozilla Firefox as a web-browser and the Open Office as office application suite.

Linux can be installed on a wide variety of computer hardware, ranging from embedded devices as mobile phones and wristwatches to mainframes and super computers. Linux is predominantly known for its use in servers; in 2007 LINUX'S overall share of the server market was estimated at 12.7%, while a 2008 estimate suggested that 60% of all the Web servers ran Linux. Most desktop computers run either Mac OS or MS WINDOWS, with Linux having only 1-2% of the desktop market. However, desktop use of Linux has become increasingly popular in recent years, partly owing to the popular UBUNTU distribution.


A Linux-based system is a modular Unix-like operating system. It derives much of its basic design from principles established in UNIX during the 1970s and 1980s. Such a system uses Linux kernel, which handles process control, networking, and peripheral and file system access. Device drivers are integrated directly with the kernel.


Users can control a Linux-based system through a command line interface (or CLI), a GUI, or through controls attached to the associated hardware. For desktop systems, the default mode is usually graphical user interface, where the CLI is available through terminal emulator windows or on a separate consol known as the virtual consol.

On desktop machines, the most popular and widely used interfaces are KDE, GNOME and Xfce; although a variety of additional user interfaces exist. Most popular user interfaces run on top of the X Windows System (often simply called as "X"), which provides the advantage of network transparency, enabling a graphical application running on one machine to be displayed and controlled from another.

Other GUIs include X Window Manager such as FVWM, Enlightenment and Window Maker. The window manager provides a means to control the placement and appearance of individual application windows, and interacts with the X Window System.

A Linux system typically provides a CLI through a Shell, which is the traditional way of interacting with a UNIX system. A Linux distribution specialized for servers may use the CLI as its only interface. A headless system that runs without even a monitor can be controlled by the command line via a remote-control protocol such as SSH or Telnet.

Mostly low-level Linux components, including the GNU, use the CLI exclusively. The CLI is particularly suited for automation of repetitive or delayed tasks, and provides very simple inter-process communication. A graphical terminal emulator program is often used to access the CLI from a Linux desktop.


Linux is a cross-platform operating system that runs on many computer models. In comparison, Windows 95 and Windows 98 run only on CPUs having the Intel architecture. Windows NT runs only on CPUs having the Intel architecture.

Second, and more important, Linux and many Linux applications are distributed in source form. This makes it possible for you and others to modify or improve them. You're not free to do this with most operating systems, which are distributed in binary form. For example, you can't make changes to Microsoft Windows or Microsoft Word - only Microsoft can do that. Because of this freedom, Linux is being constantly improved and updated, far outpacing the rate of progress of any other operating system. For example, Linux will likely be the first operating system to support Intel's forthcoming Merced 64-bit CPU.

Linux has attractive features and performance. Free access to Linux source code lets programmers around the world implement new features, and tweak Linux to improve its performance and reliability. The best of these features and tweaks are incorporated in the standard Linux kernel or made available as kernel patches or applications. Not even Microsoft can mobilize and support a software development team as large and dedicated as the volunteer Linux software development team, which numbers in the hundreds of thousands, including programmers, code reviewers, and testers.


SOLARIS is a UNIX-based Operating System which was introduced by The Sun Microsystems in 1992 as the successor to SunOS. Solaris is certified against the Single UNIX Specification. Although it was historically developed as Software, it is supported on systems manufactured by all major server vendors, and the majority of its codebase is now open source software via the Open Solaris project. Solaris is well known for originating many innovative features such as DTrace and ZFS.

DTrace is a comprehensive dynamic tracing framework for troubleshooting kernel and application problems on production system in real time. DTrace can be used to get a global overview of a running system, such as the amount of memory, CPU time, file systems and network resources used by the active processes. It can also provide much more fine-grained information, such as a log of the arguments with which a specific function is being called, or a list of the processes accessing a specific file.

In computing, ZFS is a combined file system and logical volume manager. The features of ZFS include support for high storage capacities, integration of the concepts of file system and volume management.


ZFS was designed and implemented by a team at Sun led by Jeff Bonwick. It was announced on September 14, 2004. Source code for ZFS was integrated into the main trunk of Solaris development on October 31, 2005 and released as part of build 27 of Open Solaris on November 16, 2005. Sun announced that ZFS was included in the 6/06 update to Solaris 10 in June 2006, one year after the opening of the Open Solaris community.


Unlike traditional file systems, which reside on single devices and thus require a volume manager to use more than one device, ZFS file systems are built on top of virtual storage pools called Zpools. A zpool is constructed of virtual devices, which are themselves constructed of block devices: files, hard drive partitions, or entire drives, with the last being the most recommended usage. Thus, a virtual device can be viewed as a group of hard drives. This means a zpool consists of one or more groups of drives. Block devices within a virtual device may be configured in different ways, depending on needs and space available: non-redundantly, as a mirror of two or more devices, as a group of three or more devices, or as a group of four or more devices. In addition, pools can have hot spares to compensate for failing disks. In addition, ZFS supports both read and write caching, for which special devices can be used. Solid State Devices can be used for speeding up read operations, while with super capacitors to implement a fast, non-volatile write cache, improving synchronous writes.

Finally, when mirroring, block devices can be grouped according to physical chassis, so that the file system can continue in the face of the failure of an entire chassis.

Storage pool composition is not limited to similar devices but can consist of ad-hoc, heterogeneous collections of devices, which ZFS seamlessly pools together, subsequently doling out space to diverse file systems as needed. Arbitrary storage device types can be added to existing pools to expand their size at any time. The storage capacity of all virtual devices is available to all of the file system instances in the zpool. A fixed Quota can be set to limit the amount of space a file system instance can occupy, and a Reservation can be set to guarantee that space will be available to a file system instance.


ZFS is a 128-bit file system, so it can address 18 quintillion (1.84 Ã- 1019) times more data than current 64-bit systems. The limitations of ZFS are designed to be so large that they would never be encountered, given the known limits of physics (and the number of atoms in the earth's crust to build such a storage device).


An advantage of copy-on-write is that when ZFS writes new data, the blocks containing the old data can be retained, allowing a snapshot version of the file system to be maintained. ZFS snapshots are created very quickly, since all the data composing the snapshot is already stored; they are also space efficient, since any unchanged data is shared among the file system and its snapshots.

Writeable snapshots (also known as "clones") can also be created, resulting in two independent file systems that share a set of blocks. As changes are made to any of the clone file systems, new data blocks are created to reflect those changes, but any unchanged blocks continue to be shared, no matter how many clones exist.


Dynamic striping across all devices to maximize throughput means that as additional devices are added to the zpool, the stripe width automatically expands to include them; thus all disks in a pool are used, which balances the write load across them.


In ZFS, file system manipulation within a storage pool is easier than volume manipulation within a traditional file system; the time and effort required to create or resize a ZFS file system is closer to that of making a new directory than it is to volume manipulation in some other systems.


Mac OS is the trademarked name for a series of graphical user interface-based OS developed by Apple, formerly Apple Computer for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface, the GUI. The original form of what Apple would later name the "Mac OS" was the integral and unnamed system software first introduced in 1984 with the original Macintosh, usually referred to simply as the System software.

Apple deliberately downplayed the existence of the operating system in the early years of the Macintosh for the user convenience and to help make the machine appear more user-friendly also to distance it from other operating systems such as MS-DOS, which was more hidden and technically challenging. Much of this early system software was held in ROM, with updates typically provided free of charge by Apple dealers on floppy disk. As increasing disk storage capacity and performance gradually eliminated the need for fixing much of an advanced GUI operating system in ROM, Apple explored cloning while positioning major operating system upgrades as separate revenue-generating products, first with System 7.1 and System 7.5, then with Mac OS 7.6 in 1997.

Early versions of the Mac OS were compatible only with Motorola 68000-based Macintoshes. As Apple introduced computers with PowerPC hardware, the OS was upgraded to support this architecture as well. Mac OS 8.1 was the last version that could run on a 68000-class processor. 

Mac OS X is the OS that has been included with all new Macintosh computer systems. It is the successor to Mac OS 9, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 1984. The "X" in OS X represents the Roman numeral for "10" and is a prominent part of its brand identity, is actually a Unix-based operating system.


The "classic" Mac OS is characterized by its total lack of a command line; it is a completely graphical operating system. Noted for its ease of use and its cooperative multitasking, it was criticized for its very limited memory management, lack of protected memory, and susceptibility to conflicts among operating system "extensions" that provide additional functionality (such as networking) or support for a particular device. Some extensions may not work properly together, or work only when loaded in a particular order. Troubleshooting Mac OS extensions could be a time-consuming process of trial and error.

The Macintosh originally used the Macintosh File System (MFS), a flat file system with only one level of folders. This was quickly replaced in 1985 by the Hierarchical File System (HFS), which had a true directory tree.

Most file systems used with DOS, UNIX, or other operating systems treat a file as simply a sequence of bytes, requiring an application to know which bytes represented what type of information. By contrast, MFS and HFS gave files two different "forks". The data fork contained the same sort of information as other file systems, such as the text of a document or the bitmaps of an image file. The resource fork contained other structured data such as menu definitions, graphics, sounds, or code segments. A file might consist only of resources with an empty data fork, or only a data fork with no resource fork. A text file could contain its text in the data fork and styling information in the resource fork, so that an application, which didn't recognize the styling information, could still read the raw text. On the other hand, these forks provided a challenge to interoperability with other operating systems; copying a file from a Mac to a non-Mac system would strip it of its resource fork.

In June 2005, Steve Jobs announced that Apple computers would be transitioning from PowerPC to Intel processors and thus dropping compatibility on new machines for Mac OS Classic, Jobs also announced Developer Transition Kits that included beta versions of Apple software including Mac OS X that developers could use to test their applications as they ported them to run on Intel-powered Macs. In January 2006, Apple released the first Macintosh computers with Intel processors, an iMac and the Mac Book Pro, and in February 2006, Apple released a Mac mini with an Intel Core Solo and Duo processor. On May 16, 2006, Apple released the Mac Book, before completing the Intel transition on August 7 with the Mac Pro. To ease the transition for early buyers of the new machines, Intel-based Macs include an emulation technology called Rosetta, which allows them to run Mac OS X software that was compiled for PowerPC-based Macintoshes. Rosetta runs transparently, creating a user experience identical to running the software on a PowerPC machine, though execution is typically slower than with native code.


symbian is an operating system (OS) designed for mobile devices and smart phones, with associated libraries, user interface, frameworks and reference implementations of common tools, originally developed by Symbian. It is currently the leading OS in the "smart mobile device" market

In 2008 the former of the Symbian Software Limited was acquired by Nokia and a new independent non-profit organization called the Symbian Foundation was established. Symbian OS and its associated user interfaces S60, UIQ and MOAP(S) were contributed by their owners to the foundation with the objective of creating the Symbian platform as a royalty-free, open source software. The resulting Symbian platform has been designated as the successor to Symbian OS, following the official launch of the Symbian Foundation in April 2009. The process of publishing the source code under a standard license in this case the Eclipse Public License (EPL) was slated for completion in 2010. Symbian is the world's most popular mobile operating system, accounting for 45% of Smartphone sales.


Symbian features pre-emptive multitasking and memory protection, like other operating systems (especially those created for use on desktop computers). Initially the symbian OS was created with three systems design principles in mind:

the integrity and security of user data is paramount,

user time must not be wasted, and

All resources are scarce.

To best follow these principles, Symbian uses a kernel known as the microkernel. It has a request-and-callback approach to services, and maintains separation between user interface and engine. The OS is optimized for low-power battery-based devices and for ROM-based systems. Applications, and the OS itself, follow an object-oriented design: Model-view-controller (MVC).

Later OS iterations diluted this approach in response to market demands, notably with the introduction of a real-time kernel and a platform security model in versions 8 and 9.

There is a strong emphasis on conserving resources which is exemplified by Symbian-specific programming idioms such as descriptors and a cleanup stack. There are similar techniques for conserving disk space (though the disks on Symbian devices are usually flash memory). Furthermore, all Symbian programming is event-based, and the CPU is switched into a low power mode when applications are not directly dealing with an event. This is achieved through a programming idiom called active objects. Similarly the Symbian approach to threads and processes is driven by reducing overheads.

The Symbian kernel supports sufficiently-fast real-time response to build a single-core phone around it-that is, a phone in which a single processor core executes both the user applications and the signaling stack. This is a feature which is not available in Linux. This has allowed Symbian's new phones to become smaller, cheaper and more power efficient than their predecessors.

Released early 2005, the Symbian included many new security related features, including platform security module facilitating mandatory code signing. The new ARM binary model meant that developers need to retool and the security changes mean they may have to recode. The 3rd Edition phones have Symbian OS 9.1. Currently Sony Ericsson is shipping the M600 and P990 based on Symbian OS 9.1. The earlier versions had a defect where the phone hangs temporarily after the owner sent a large number of SMS's. However, on 13 September 2006, Nokia released a small program to fix this defect. Support for Bluetooth 2.0 was also added.


Symbian OS was subject to a variety of viruses, the best known of which is CABIR. Usually these send themselves from phone to phone by Bluetooth. So far, none have taken advantage of any flaws in Symbian OS - instead, they have all asked the user whether they would like to install the software, with some what prominent warnings that it can't be trusted.

However, with a view that the average mobile phone user shouldn't have to worry about security, Symbian OS 9.x adopted a UNIX-style capability model (permissions per process, not per object). Installed software is theoretically unable to do damaging things (such as costing the user money by sending network data) without being digitally signed - thus making it traceable. Commercial developers who can afford the cost can apply to have their software signed via the Symbian Signed program. Developers also have the option of self-signing their programs. However, the set of available features does not include access to Bluetooth, IrDA, GSM Cell-ID, voice calls, GPS and few others. Some operators have opted to disable all certificates other than the Symbian Signed certificates.

Article name: Operating Systems And Microsoft Windows Computer Science essay, research paper, dissertation