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operating system

Operating System Market Share 2009

The following has been adapted from: Franklin, Curt, and Dave Coustan. "How Operating Systems Work." 14 August 2000. HowStuffWorks.com. <http://www.howstuffworks.com/operating-system.htm> 09 January 2010 and http://www.webopedia.com/term/o/operating_system.html

­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 systems. The operating system (OS) is the first thing loaded onto the computer -- without the operating system, a computer is useless.

More recently, operating systems have started to pop up in smaller computers as well. If you like to tinker with electronic devices, you're probably pleased that operating systems can now be found on many of the devices we use every day, from cell phones to wireless access points. The computers used in these little devices have gotten so powerful that they can now actually run an operating system and applications. The computer in a typical modern cell phone is now more powerful than a desktop computer from 20 years ago, so this progression makes sense and is a natural development.
The purpose of an operating system is to organize and control hardware and software so that the device it lives in behaves in a flexible but predictable way. In this article, we'll tell you what a piece of software must do to be called an operating system, show you how the operating system in your desktop computer works and give you some examples of how to take control of the other operating systems around you.

The operating system is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard and mouse, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.
For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.

Operating systems can be classified as follows:
      • multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
      • multiprocessing : Supports running a program on more than one CPU.
      • multitasking : Allows more than one program to run concurrently.
      • multithreading : Allows different parts of a single program to run concurrently.
      • real time: Responds to input instantly. General-purpose operating systems, such as Window, Mac OS X and Linux, are not real-time.

Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run.

Most operating systems today use a graphical user interface allow you to enter commands by pointing and clicking at objects that appear on the screen, for example, make new folder or to locate a file to open.
Not all computers have operating systems. The computer that controls the microwave oven in your kitchen, for example, doesn't need an operating system. It has one set of tasks to perform, very straightforward input to expect (a numbered keypad and a few pre-set buttons) and simple, never-changing hardware to control. For a computer like this, an operating system would be unnecessary baggage, driving up the development and manufacturing costs significantly and adding complexity where none is required. Instead, the computer in a microwave oven simply runs a single hard-wired program all the time.

For a very detailed account of operating systems, please go to the teach-ICT A level site.



The running of two or more programs in one computer at the same time. The number of programs that can be effectively multitasked depends on the sophistication of the operating system, the speed of the CPU and the speeds and capacities of memory and disk.


(v.) To load the first piece of software that starts a computer. Because the operating system is essential for running all other programs, it is usually the first piece of software loaded during the boot process.

Boot is short for bootstrap, which in olden days was a strap attached to the top of your boot that you could pull to help get your boot on. Hence, the expression "pull oneself up by the bootstraps." Similarly, bootstrap utilities help the computer get started.

(n.) Short for bootstrap, the starting-up of a computer, which involves loading the operating system and other basic software. A cold boot is when you turn the computer on from an off position. A warm boot is when you reset a computer that is already on.

For a detailed presentation on how computers boot up, please go to Gustavo Duarte's blog.

Software, computers, and business.


These are programs, often shareware, freeware or supplied with the OS, for maintaining the computer.
Here are a few Mac OS X examples:

  • Chipmunk: A fast and easy to use tool to find and remove duplicate files. Files are automatically compared byte by byte to determine if two given files are true duplicates. Intelligent deleting can operate on all files inside a folder that exist outside of it or vice versa.
  • ShowDesktop: Similar to Windows Desktop, now you can do your own and drop on the Dock. Just put the Application in your hard drive and grab its icon to the dock, anywhere you like. That’s it! when you have any quantity of windows opened, just click on the icon and now you’re free to see your desktop anytime. PS: All applications are closed, could say minimized.

disk format

The following has been adapted from the wikipedia entry.

Disk formatting is the initial part of the process for preparing a hard disk or other storage medium for its first use. The disk formatting includes setting up an empty file system. A disk formatting may setup multiple file systems by formatting partitions for each file system. Disk formatting is also part of a process involving rebuilding an entire disk from scratch.

Formatting a disk for use by an operating system and its applications and files involves two quite different types of formatting. First, a low-level (closer to the hardware) formatting program will mark the surface of the disk with sector numbers and other information to be used later, in normal operations, by the disk controller. This is intended to be the permanent foundation of the disk, and is often completed at the factory.

High-level formatting occurs during operating system installation, or when adding a new disk. This inscribes the file system format. Disk and distributed file system will specify an optional boot block, and various volume and directory information for the operating system.
A high-level format procedure is sometimes performed on a functioning disk to erase the contents of the hard drive. This is commonly termed a "reformat". While this may not completely erase all data from the drive, iit erases critical areas, such as the boot sector and partition table. This gives the appearance of an empty disk to the operating system, making any existing contents unavailable by normal methods.
Reformatting often carries the implication that the operating system and all other software will be reinstalled after the format is complete. Rather than fixing an installation suffering from malfunction or security compromise, it is sometimes judged easier to simple erase everything and start from scratch. Various colloquialism exist for this process, such as "wipe and reload", "nuke and pave", "reimage", etc.

virus scan programs


Think of this analogy: storing books in a library. If you have a set of encyclopedias, it would be prefereable to store them in one location in order. However if you did not have enough shelf space, you may have to put each encyclopedia onto different shelves in different parts of the library. You would then have to remember where each one is located and if you needed to access a number of the books, you would spend quite a long time moving around the library to locate each individual one. It would be better to reorganise the library to put all the collections together and put books into categories to store in the same place. What happens when a book is returned? Ideally the book would be shelved back in the same location from where it was taken. However what would happen if you received new books and there was not enough space to store it in the right location? You would have to place this on an overflow shelf or reorganise the shelves to accommodate the new books which is time consuming. What would happen if you randomly placed books on the shelves but kept a record or note of where each book was? To locate a book, you would have to check where it was first and then go and find it. This would take a long time.

Now think about saving files on a hard drive. When a file or data is saved on your hard drive, it is not always stored in one location. It is often broken into smaller sections and each section is stored in various locations on the hard drive. Ideally it would be better to have the sections of the file stored close to each other so that when the file is accessed it is quicker to load the sections required into RAM. Think about a work-in-progress file that you have saved on your hard drive, for example, a word processed file. What happens when you edit the file and make it bigger? When you save this file, it may not save back to its original location but may save parts of the files all over the hard drive where there is space. If you delete a file, then the spaces the the file occupies becomes available and the next time you save a file, for example your editing word processed file, parts of this may be saved in the deleted file spaces. Eventually the hard drive becomes very disorganised or fragmented.

Defragmentation is the he process of reorganising the way that your files are stored on a hard drive.

This wikipedia entry has a good diagram to help explain defragmentation.