Introduction To Operating System Computer Science Essay

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The operating system of the computer can be defined for the extension of the computer hardware, software modules, and a collection of more convenient and easier to use other programs. In other words, it "converts" the computer's hardware resources of the virtual machine's virtual resources

The operating system is a software layer, which is responsible for a computer operating technology. It protects the user's machine, the machine's operation, from low-level details, and often need facilities. What is the operating system there is no uniform definition. You can see it as the software has been installed on a machine, and then add any of your own. Typically, some of the key elements of the operating system: (a) layer of software driven computer hardware, disk drives, keyboard, and screen; (ii) a file system, it provides the logical way to organize files and (iii ) a simple command language, so users can run their own programs to deal with their own files in a simple way. Some operating systems also provide a text editor, compiler, debugger and other tools. Since, the operating system (OS) is responsible for a computer, all the requests to use its resources and equipment needed by the OS.

Define Question 1

Most desktop or laptop PCs come pre-loaded with Microsoft Windows. Macintosh computers come pre-loaded with Mac OS X. many corporate servers use the Linux or UNIX operating system. The operating system (OS) is the first thing loaded onto the computer without the operating system, a computer is useless.

Answer Question 1

When you turn on your computer. It's nice to think that you're in control. There's the trusty computer mouse, which you can move anywhere on the screen, summoning up your music library or Internet browser at the slightest whim. Although it's easy to feel like a director in front of your desktop or laptop there's a lot going on inside, and the real man behind the curtain handling the Necessary tasks is the operating system.

*Microsoft Windows

Windows is the operating system sold by the Seattle-based company Microsoft. Microsoft, originally christened "Traf-O-Data" in 1972, was renamed "Micro-soft" in November 1975, then "Microsoft" on November 26, 1976. Microsoft entered the marketplace in August 1981 by releasing version 1.0 of the operating system Microsoft (MS-DOS), a 16-bit command-line operating system.

The oldest Microsoft operating system is MS-DOS (Microsoft Disk Operating System). MS-DOS operating system is a text-based. User input commands, rather than using the more user-friendly graphical user interface (GUI) today. Although it looks very basic, MS-DOS is a very powerful operating system. There are many the advanced applicable to the MS-DOS applications and games. The basis of a version of Windows, MS-DOS. Many advanced administration tasks in Windows can only use MS-DOS.

The Windows XP operating system is a dynamic and continually changing operating

System's with new security patches and hot fixes being released often. In a normal

Production environment, it is highly recommended that you maintain a patching schedule to keep your systems up-to-date. For the purposes of this book, it is important that you do not patch your system. Because this system will be vulnerable to most of the exploits that have been discovered since Windows XP was first released, it is extremely important that you do not connect it to a production network. Several patches will cause issues when completing various labs in this book. By following the installation guide, you are assured of getting the maximum value out of the activities covered throughout this book.

*Mac OS X

Mac OS is a computer operating system of Apple Computer's Macintosh line of personal computers and workstations. A popular features of its latest version of Mac OS X, is a desktop interface with some 3-D appearance features. OS X has a modular design in order to make it easier to add new features, the operating system in the future. It runs UNIX applications, as well as older Mac applications.

Mac OS X is an operating system (OS) that manages just about everything on or connected to a Macintosh (Mac) computer such as files, applications (programs), and devices such as monitors and printers. In essence, the OS defines how the computer will function and how it is presented to the user.

Mac OS X is the operating system for Apple's Macintosh computers and it is based on the Unix-based OPENSTEP operating system developed by NeXT Software which Apple acquired in the 1990's.  All new Macintosh computers run Mac OS X.  Mac OS X offers a powerful secure UNIX based core that is able to run a vast collection of software and presents to the user an easy to use graphical user interface (GUI) called Aqua.  Furthermore, Mac OS X allows users to take advantage of an open-source UNIX based operating system along with the ease of use inherent to the Macintosh.

*Microsoft Windows .vs. Mac OS X

Depends on what you want to use your computer. If you want to surf the Web security, then you may want to get the Mac OS-X-based systems. If you're looking for games, Internet compatibility, a fast computer, then you will want to go computer Windows XP.

Yes, it has a beating unlike whole infested Windows XP security issues, but at this point most of the Mac is still the maximum speed limit slightly higher than the 1.25 GHz G4 processor. The new Mac G5 processor with a maximum of 800 front-side bus speeds, and broke the 64-bit processor 2 GHz barrier. Apple continues borrowing ideas from Windows XP and the maintenance of its security features, they will eventually shine Microsoft.

But, to tell the truth ... I've been watching Apple Mac processors and operating systems since the 1980s and assigned the management team and the company's vision and direction have a terrible reputation, so obviously stupid, pathetic, and I own a brand new Mac Mini, at the top of a new custom built-in Pentium 43.2 GHz processor running Windows XP Professional, Apple has not re-earned my trust of ten thousand tons stupid thing it did in the past, cost me and many of us some cash. Probably a few years ago, Apple Computer to fully redeemed itself I switched to Windows and Mac operating systems, Windows XP is more consumers and consumer industry recognized platform than MAC OS-X.


Today Linux has joined the desktop market. Linux developers concentrated on networking and services in the beginning, and office applications have been the last barrier to be taken down. We don't like to admit that Microsoft is ruling this market, so plenty of alternatives have been started over the last couple of years to make Linux an acceptable choice as a workstation, providing an easy user interface and MS compatible office applications like word processors, spreadsheets, presentations and the like.

On the server side, Linux is well-known as a stable and reliable platform, providing database and trading services for companies like Amazon, the well-known online bookshop, US Post Office, the German army and many others. Especially Internet providers and Internet service providers have grown fond of Linux as firewall, proxy- and web server, and you will find a Linux box within reach of every UNIX system

Administrators who appreciates a comfortable management station. Clusters of Linux machines are used in the creation of movies such as "Titanic", "Shrek" and others. In post offices, they are the nerve centers that route mail and in large search engine, clusters are used to perform internet searches. These are only a few of the

Thousands of heavy-duty jobs that Linux is performing day-to-day across the world.

*Microsoft Windows .vs. Linux

For Linux although the majority Linux variants have improved dramatically in ease of use, Windows is still much easier to use for new computer users. The majority of Linux variants and versions are notoriously reliable and can often run for months and years without needing to be rebooted. Linux has a large variety of available software programs, utilities, and games. However, Windows has a much larger selection of available software. Linux is and has always been a very secure operating system. Although it still can be attacked when compared to Windows, it much more secures. Many of the Linux variants and many Linux programs are open source and enable users to customize or modify the code however they wish to.

For, microsoft windows has made several advancements and changes that have made it a much easier to use operating system, and although arguably it may not be the easiest operating system, it is still Easier than Linux. Although Microsoft Windows has made great improvements in reliability over the last few versions of Windows, it still cannot match the reliability of Linux. Because of the large amount of Microsoft Windows users, there is a much larger selection of available software programs, utilities, and games for Windows. Although Microsoft has made great improvements over the years with security on their operating system, their operating system continues to be the most vulnerable to viruses and other attacks. Microsoft Windows is not open source and the majority of Windows programs are not open source.

Define Question 2

If your computer does not have to run a program or random access memory (RAM) required for operation, Windows uses virtual memory to compensate for the virtual memory of your computer's RAM with temporary space on the hard disk. Insufficient RAM, virtual memory data from RAM to move to the space known as paging file. Mobile data and can be released from the paging file RAM to complete its work.

Interrupt processing is at the core of modern operating system implementation. You must make sure that you thoroughly understand it.

Answer Question 2a

What is Virtual Memory?

The memory of your computer hardware used to load the operating system and run the program. It consists of one or more RAM chips, each having a plurality of memory modules. The actual amount of memory in the computer is the limited amount of RAM installed. Common memory is size of 256MB, 512MB and 1GB.

A limited RAM your computer, it is possible run out of memory, running too many programs at the same time. This is the virtual memory. Virtual memory your computer will be increased by expanding the address space, available memory "or memory data can be stored in places. This is achieved by the use of additional hard disk space for memory allocation. However, a lot of the hard drive is slower than RAM; the data stored in virtual memory must be mapped to real memory to use.

The more RAM your computer has, the faster your programs will generally run. If a lack of RAM is slowing your computer, you might be tempted to increase virtual memory to compensate. However, your computer can read data from RAM much more quickly than from a hard disk, so adding RAM is a better solution.

Paging:-Paging is a virtual memory scheme which is transparent to the program at the application level and which divides memory into fixed-size blocks, such as 4 Kbytes.

Segmentation: The segmentation memory management scheme imposes a greater book-keeping burden on the application, and refers to memory using segments of variable size. 

*Virtual Memory with Paging

The paging is to allow the process of the non-continuous physical address of a memory management program. Paged memory is divided into fixed-size pages is a memory management technology. Paging is for faster access to data. When a program requires a page, it is as an OS copy a number of pages in the main memory from the storage device to the main memory. Paging allows the physical address space of a process is not continuous. OS is executing an operation for the data in the main memory from the auxiliary storage device for storage and retrieval. Paging is a memory management program. The data is retrieved from the storage medium by the OS; the same size of the block is called a page. Paging allows the physical address space of the process, the non-continuous. The whole program will accommodate the stored contiguously.

Paging is dealing with external fragmentation problems. This is allowed in the logical address space of a process is not continuous, which makes the process of physical memory allocated.

*Virtual Memory with Segmentation

The concept of segmentation is based on the common practice by programmers of structuring their programs in modules-logical groupings of code. With segmented memory allocation, each job is divided into several segments of different sizes, one for each module which contains pieces that perform related functions. A subroutine is an example of one such logical group. This is fundamentally different from a paging scheme, which divides the job into several pages all of the same size each of which often contains pieces from more than one program module.

A second important difference is that main memory is no longer divided into page frames because the size of each segment is different - some are large and some are small. Therefore, as with the dynamic partitions, memory is allocated in a dynamic manner.

When a program is compiled or assembled, the segments are set up according to the program's structural modules. Each segment is numbered and a Segment Map Table (SMT) is generated for each job - it contains the segment numbers, their lengths, and (when each is loaded into memory) its location in memory.

*Compare Paging and Segmentation

When paging, the memory is divided into equal-sized section of the page, and the size of the memory segment (which is why the length of each segment attributes) may vary. The determination of the size of the segment is based on the address space required by a process, and a process's address space is divided into a number of pages of equal size in the paging. The security of the divided segments, while the paging does not provide such a mechanism.

a) Paging- Paging is a virtual memory management scheme, in which the physical memory is divided into fixed-size blocks, called frames, and virtual memory is divided into fixed-size blocks called pages. Whenever a program is loaded into memory, the page has been loaded into the frame.

b) Segmentation - Computer memory is allocated in various sizes (segments) depending on the need for address space by the process. These segments may be individually protected or shared between processes. Commonly you will see what are called "Segmentation Faults" in programs, this is because the data that's about to be read or written is outside the permitted address space of that process.

*What is interrupt?

An interrupt is a dynamic event that needs prompt attention by the CPU. Usually an interrupt only needs a short period of CPU time to serve it. After that the original process can resume its execution

There are two types interrupting events: hardware interrupts that are those issued by I/O device controllers when they need CPU to process I/O data, and software interrupts, also called traps, that are raised when the current process executes a special trap instruction to indicate that something wrong has happened or the process needs special service from the operating system (like performing some I/O operation).

Only a limited number of types of interrupts are defined. For each type of I/O devices, there is a special program called an interrupt handler to serve the interrupt requests from these devices. For all software traps, there is also a special trap handler defined.

Each type of interrupt has an associated priority level. A running process would only be interrupted by an interrupt source or trap of higher priority. When the CPU is executing an interrupt handler, the interrupt handler may be further interrupted by an interrupt source of even higher priority.

*Interrupt Processing

Interrupt mechanism means for the engine of the coordination between the multi-channel of the I-stream engine, and a channel subsystem. Interrupt is handing over control of the hardware-enforced workflow engine. Usually occurs after the interrupt instruction completion, and before the start of the next instruction. Eventually, return to the interrupted code, without losing data. Interrupt class does not prevent them to be set in the device controller and the device's interrupt generating a signal in an I-stream engine is suppressed. In essence, these signals are stacked within the channel subsystem, which signal to any I-stream engine is willing to accept the interrupt.

The program status word (PSW), including control instruction sequencing and to determine the status of the I-flow engine instruction address and other information. A PSW also used to prevent or allow interrupt bit. An I-stream engine control, in addition to the current PSW, PSW interrupt associated with each class of PSW. There are six classes of interrupt may:


Machine check




Supervisor Call (SVC)


Now a day, computers are played a part of our life. In fact, computer just a scrap metal if without Operating System, Operating System is very important. A good operating system makes your life easy more efficiently. For my recommendation, I suggest you use Windows Operating system. Windows Operating system is easy to use and have a good interface. Windows Operating system is allowed you do anything you want.

Virtual memory is one of the most important concepts that must be well understood to know how the operating system actually allows large programs (programs larger than the size of main memory) to run without any problem.

As you know that the program is divided into several pages of a fixed size. In ancient times to run a program every page of this program must be present in main memory, but over time and scheduling multiple image sizes entered and program increased dramatically so it was not possible to keep all pages of all programs in main memory, but each program can have all your pages to secondary storage (disk). Virtual memory so we can keep only the pages needed today by our program and keep the rest of secondary storage pages, so whenever there is need for the page can be fetched from disk.

When an event or a higher priority process, require prompt attention of the CPU, you can interrupt the execution of the current process CPU to save your key state in memory or on the hard drive, do one CPU, and interrupt handling application summary of the original process, to restore its state in memory, and register