Operating System Run On Pcs Laptops Computer Science Essay

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Windows 8 change the old style of desktop in to brand new touch screen. In windows 8 mostly everything on the start screen. Tiles on the start screen keep connected with apps, people and alive with the latest info.

Touch Mouse and keyboard:-

Windows 8 introduced the touch keyboard and mouse because now a day's most of the users like touch devices. Windows 8 support this feature because it used also in tablets and smart phones. By this feature user feels the apps move around fast and smoothly form one place to another.

Apps Store:-

Windows 8 introduced new feature of store where u can find any type of software according to your requirement. It has thousand of apps with different category.


This application is about music lovers. It has thousand of songs and access the songs all over the world.



The old style of desktop still there with taskbar and folder icons. The improvement is they have new task bar and streamlined file management.


Windows 8 is more secure than other because of windows firewall, windows defender, windows up to date and smartscreen filter.


Windows 8 is boost up faster and switch between the apps more efficiently than windows 7.

Windows 8 start up time is 21 sec

Windows 7 start up time is 45 sec

Windows 8 shutdown time is 7 sec

Windows 7 shutdown time is 13 sec

Why windows 8

Everything You Want:-

All data can be synchronized through the cloud you can access your data at once and everywhere.

Play As Hard As It Works:-

Windows 8 gives you a fast and safe browsing, watch movie, play games and many more you done on a sing system (PC).


Windows 8 runs all files that you run or use file on windows 7.

Category of windows 8


In windows 8 snap technique in used for multi-tasking. It's a new feature in windows 8 by using this feature the user run one or more apps side by side at a time in single screen.

Most important thing is this feature available only high resolution monitor. This OS run more than one program so this OS is called multi-tasking OS.


In multi-programmed system multiple jobs can execute at a time. It's like a batch file system but there is interaction between user and computer during execution of job. User can interrupt the job in this system.

It does not mean that the program run same time but the OS divided the time for each program according to their priorities. All this process is working very fast so user think it work at the same time.

Windows 8 run more than one program so it is multi programming OS.


Windows 8 is a multi-programming OS due to this reason it requires that the processor is allocate the time period of each program and de-allocate at appropriate time. If the running process is de allocate at execution time. It done in such a way that later it can be restarted easily as possible.

Two possible way of windows 8 OS to allocate or de allocate of the process

The process issues a system call (sometimes called a software interrupt); for example, an I/O request occurs requesting to access a file on hard disk.

A hardware interrupt occurs; for example, a key was pressed on the keyboard, or a timer runs out (used in pre-emptive multitasking).

The stopping of one process and starting (or restarting) of another process is called a context switch or context change. In many modern operating systems, processes can consist of many sub-processes. This introduces the concept of a thread. A thread may be viewed as a sub-process; that is, a separate, independent sequence of execution within the code of one process. Threads are becoming increasingly important in the design of distributed and client-server systems and in software run on multi-processor system.


In Windows 8, any program has the ability to allocate memory as "low priority." This is an important signal to Windows that if there is memory pressure, Windows can remove this low priority memory to make space, and it doesn't affect other memory required to sustain the responsiveness of the system.

Windows 8 has a better scheme for the prioritization of memory allocations made by applications and system components. This means that Windows can make better decisions about what memory to keep around and what memory to remove sooner.

For example, antivirus programs (AV) do various checks on files when they are being opened by other programs. The memory that the AV program allocates to check virus signatures is usually a one-time allocation (it is unlikely that specific memory will be needed again). On Windows 7, the memory is treated as if it had the same priority in the system as other memory (say, memory allocated by a running instance of Microsoft Excel). If memory became scarce, Windows 7 could end up removing the memory that helps another running application (like Excel) stay responsive for the user, which wouldn't be the best choice for system responsiveness in this case.

Start on demand:

Windows 8 addresses that by including a new "start on demand" model. Services such as Windows Update and Plug-and-Play will only be started when needed-for example, when it's time for the daily check for updates, or when new hardware has been connected-and will stop running when no longer necessary. The result is that, most of the time, memory usage is reduced.

Memory Protection

Memory that belongs to a process is implicitly protected by its private virtual address space. In addition, Windows provides memory protection by using the virtual memory hardware. The implementation of this protection varies with the processor, for example, code pages in the address space of a process can be marked read-only and protected from modification by user-mode threads.

Copy-on-Write Protection:

Copy-on-write protection is an optimization that allows multiple processes to map their virtual address spaces such that they share a physical page until one of the processes modifies the page. This is part of a technique called lazy evaluation, which allows the system to conserve physical memory and time by not performing an operation until absolutely necessary.

For example, suppose two processes load pages from the same DLL into their virtual memory spaces. These virtual memory pages are mapped to the same physical memory pages for both processes. As long as neither process writes to these pages, they can map to and share, the same physical pages, as shown in the following diagram.

Boxes and arrows of process 1 and 2 pages mapped to same physical memory

If Process 1 writes to one of these pages, the contents of the physical page are copied to another physical page and the virtual memory map is updated for Process 1. Both processes now have their own instance of the page in physical memory. Therefore, it is not possible for one process to write to a shared physical page and for the other process to see the changes.