Three Main Operating Systems Computer Science Essay

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Carry out a critical analysis on three main operating systems (Linux OS, Windows Vista and Symbiam OS). Compare and contrast the history, overview, system structure, processes and threads, memory management, application and security issue of each operating system. Comment on the strength and weakness of each OS considered.

Based on your group analysis proposed a new OS architecture that would incorporate the strength(s) of the existing OS and deal with the weakness(es) of the existing OS. For this work, you are free to use internet resources, research publications, books and lecture resources but proper referencing must be used.

Report requirements

You are required to submit one report each group. The report should not be more than 4 A4 papers Marks would be awarded for good referencing (You will be introduced to Harvard style reference using Endnote software - not compulsory)

Note that students would only be awarded maximum mark for a clear, concise, accurate and well reference write up.

Coursework: Operating Systems- State of the art

Computers have been known to be in use for many centuries in one form or another. The earliest computer was an analog computer made by the Greeks around 100BCE [1] . It has been since then that computers and computer functions have developed to what they are today. There are many Operating systems on the market today, all at competitive rates with different offers right across the world. With the amount of latest gadgets being released every year, it is important to consider the Operating systems of all electronic items. The three main operating systems competing in the market today are Windows Vista, Linux and Symbian, all with specific hardware and software applications.

History of each OS

Timeline taken from: first Windows operating system to be released was the 'Interface manager' also referred to as Microsoft Windows in the early 1980's [2] by Microsoft, which had very limited properties and functions. It was around this time that the computer market become competitive, as Apple computer had more functionality. As a result, Windows kept bringing out more up to date operating systems to meet the end user requirements, which have changed tremendously over the years. The timeline shown on the right shows the number of operating systems that have been released by Microsoft until 2001. In 2007 Windows Vista was released and the latest version, Windows 7 is about to be released. Out of all the operating systems, Windows 98 as the most successful OS to be released and it was since then that many computer products where released to be compatible with Windows devices and there has also been a rises in the number of Windows mobile users, increasing the popularity of Windows. The table below shows the market shares that Windows have had for all their Operating Systems, taken








August 2009

August 2009

February 2009

December 8, 2008

All versions





Shortly after the introduction of the first Windows OS, Linux was released in 1991 [3] , in Helsinki by Linus Torvalds. He developed the Unix operating system, which was a basic operating system that was compatible with different hardware [4] . Unix systems were very expensive and were based on 'mainframes and minicomputers' [5] . Minix was another operating system created in attempt to create cheaper and more portable version of the Unix, however it was cheap and had minimal functions. Linux was developed as a result of combining the software of Unix and the idea of Minix, making it a more user friendly system, so that the Unix functions can be used at home and also gives the end user a choice of software and it is also compatible with a big range of hardware, making it an ideal operating system. Linux is known as 'only operating system in the world covering such a wide range of hardware' [6] leaving their competitors Microsoft behind. Linux also has worked alongside with the GNU GPL (General public license) to "to integrate GNU components with Linux to make a


Operating system and functions


Psion for PDA's created by David Potter


EPOC (Electronic piece of cheese)

Several versions released with different Graphical user interfaces for net books, net pads and phones.


ER5u Ericsson R380 phone released. Games installed onto phones

2001- present

Symbian OS were released in numerous versions for many phone companies, especially for its partner Nokia, with Bluetooth, supporting different languages, java support, cameras, WiFi support, memory management and their latest function is to watch digital television broadcasts.fully-functional and free operating system" [7] . These leads to a lot of controversy with their competitor Microsoft, as their operating systems aren't free.

Finally, Symbian OS is an embedded operating system and is more associated with mobile phones and smart phones and was designed to meet the requirements and fulfill the fashion of portable 'pocket' devices. It is the world's most popular mobile operating system [8] . The table on the right shows the development of the Symbian operating systems and how the portable devices have developed functionality. Symbian OS are mainly used in Nokia mobile phones, as phones are their target market devices, unlike Windows which targets computers.

System structure of each OS

Windows Vista OS has a

The structure of the Linux OS is based on the Kernel, which is considered to be the heart of the system. It controls the access to the CPU, whose functions are to manage memory space and link to peripherals. The structure of the OS is summarized in the diagram on the right, showing all the layers required in the system allowing the operating system to work.

All Linux systems are built the same way as other operating systems, as they all have the same functions and do the same job. This increased the amount of compatibility for different software and hardware, increasing the amount of flexibility. The operating systems are also made up of different pieces of hardware, such as the RAM, CPU, motherboard which all allows the computer to run efficiently. All computers have a Kernel. This acts as the interface between the hardware and the operating system, allowing them to process any input and provide the correct output, including any peripherals that may be required. The Kernel is also responsible for allocation of resources, such as allocating memory to running programs and managing files and allocating resource time to each user. A Linux OS has built in commands that are used daily by the operating system, allowing basic computer functions to be achieved, such as file manipulation.

UI Framework Layer (Top)

Application Services Layer

Java ME

OS Services Layer

generic OS services

communications services

multimedia and graphics services

connectivity services

Base Services Layer

Kernel Services & Hardware Interface Layer

The microkernel architecture means that the minimum necessary is within the kernel to improve robustness, availability, and responsiveness. It contains a scheduler, memory management, and device drivers, but other services like networking, telephony, or file system support are placed in the OS Services Layer or Base Services Layer.The Symbian OS system has a more specific structure. The layers of the OS are listed below:

Taken from:

Processes and threads of each OS

The processes of the three operating systems are quite different. The process 'provides the resources needed to execute a program' [9] and in Windows and Linux, the programs are executed in different ways. Both processes and threads of an OS are described here:

"A process has a virtual address space, executable code, open handles to system objects, a security context, a unique process identifier, environment variables, a priority class, minimum and maximum working set sizes, and at least one thread of execution. Each process is started with a single thread, often called the primary thread, but can create additional threads from any of its threads." [10] 

"A thread is the entity within a process that can be scheduled for execution. All threads of a process share its virtual address space and system resources. The thread context includes the thread's set of machine registers, the kernel stack, a thread environment block, and a user stack in the address space of the thread's process. Threads can also have their own security context." [11] 

The thread that is used by Windows OS is the basic executable unit, whereas the Linux OS has a slightly different process. Linux systems have threads, processes and a lightweight process. The table below is a comparison of the threads and processes in Windows and Linux.




























Using Sys V semaphores, Waitforsingleobject/multipleobject

can be implemented

Context specific





MappableTable 1: Process mapping [12] 



























Context SpecificTable 2: Threads mapping [13] 

Symbian's memory protection is called the thread and unlike Windows and Linux, the threads are scheduled, making the memory protection more effective. This allows many processes to be running at once. Some platforms use active objects, as they are designed for more effective performance, as they are made using multi-threaded codes. On the Symbian C++ platform, the threads are scheduled with the most important one running first. [14] 

Memory management of each OS

Applications of each OS

Windows Vista is compatible with many different applications. Microsoft office, Frontpage and Professional are especially designed packages to suit different end users and used for different purposes. Windows comes with some standard applications, such as Windows media player, paint and games pre-installed. Most electronic devices are made compatible and standard to Windows OS, such as digital cameras, mp3 players and other accessories.

Security issues of each OS

Windows has been known for many security breaches by a very high number of viruses, all at a range of risk levels. The number of risks increased when network connections were introduced, as this allowed the viruses to spread rapidly from one computer to the next, having disastrous consequences. Also, access to the Internet made all the computers connected at a higher risk to viruses. As Windows is a very popular OS, with at least one computer in every household, means that the operating system is a popular target for virus creators, with at least 1,000 new viruses being created every year.

To avoid this, Windows update program automatically updates the computer with new security patches, to try to reduce the risk of viruses attacking your PC. Windows file permissions and Windows defender antispyware are used to prevent unauthorized access to files and details. On the other hand, although Microsoft is taking all these precautions, they do not seem to be enough as is quoted here:

"In an article based on a report by Symantec, has described Microsoft Windows as having the "fewest number of patches and the shortest average patch development time of the five operating systems it monitored in the last six months of 2006." Furthermore the number of vulnerabilities found in Windows has significantly increased" [15] 

Also, Linux seems to have major flaws in its system, when we are considering the possible security risks involved as an article states:

"Linux security experts take issue with recent reports from and from that suggest Windows is more secure than Linux, based on statistics from SecurityFocus. But one Linux security guru says he's seeing at least a 10% increase in Linux security vulnerabilities reported in the last six months, mostly due to greater awareness on the part of Linux vendors." [16] 

Most of the argument with the increase in vulnerabilities is based on the fact that virus creators and hackers now have such a wider range of choice then previously. With the aid of the Internet they can access millions of computers around the world. Linux security is based on the feedback of their customers, so it is only when a problem occurs and a customer complains that they see the vulnerabilities and then decide whether it is relevant, as they have a much smaller audience than Windows.




Prevents automatic startup from antivirus applications, making the phone more vulnerable to other viruses.

Locknut B

Prevents any applications from being installed in the phone

Mabir A

Same as Cabir, except can also be transferred by sending MMS.

Fontal A

Causes loss of data and interrupts reboot filesSymbian OS were vulnerable to many viruses, due to the invention of Bluetooth, which allowed mobile phones to connect to each other allowing files to be sent and in many cases viruses to be sent. The most popular one being a virus called 'Cabir' [17] , the first virus that infected mobile phones, though it did not do any damage. To prevent this antivirus software were installed onto mobile devices and when applications are installed, warning signs come up, so that the end user knows if by installing that application their device would be at risk of being attacked by viruses. Some phones only allow applications with Symbian certificates to be installed. The table on the left lists other viruses associated with the Symbian OS [18] .

Overview of each OS

Out of all three of the Operating Systems, the best Operating system is probably Windows, as their beta testing is better than Linux or Symbian, as they are not as popular. They all have just as many security problems, all with major flaws, due to an increase in opportunities to cause damage to a bigger audience. Symbian has a different more complicated structure, whereas the structures for Linux and Windows have a more similar structure and process in terms of threads and processes.

Proposed group OS architecture

Justification of proposed OS architecture