Without an operating system your computer would be useless!A computer contains an Operating System on its Hard Drive. This isloaded after the computers boot up sequence, and allows the userto use the keyboard and mouse to be able to store data to a harddisk driveYou can find operating systems in Personal Computers, SatNavigation Systems, Network Servers, Mobile Phones, GameConsoles and even CARS!
• The main function of a Operating System are: • Processor Management • Memory Management • Device Management • Storage Management • User Interface
If you’re a user who has many different applications open ormaybe you might be just browsing the internet and have lots ofdifferent tabs open.For the computer to be able to switch between theseapplications or to switch between the tabs the Operating Systemhas to switch between different processes thousands of times asecond.
RAM has a limit, however your operating system may need moreprimary memory than there physically is, therefore the computeruses virtual memory.A good example is if a computer has 2GB of RAM as primarymemory, however it could have up to 4GB of Virtual Memory. Thisworks by the operating system setting aside part of its secondarystorage on a storage medium e.g. hard disk/memory stick to beused as temporary memory store. This area is know as thetemporary memory store and is called a page file or a swap file.The operating system will use this page file once all the availableRAM has been used up in our instance if the 2GB of RAM is usedup then the OS will start to store chunks of the memory on thesecondary storage. The chunk itself is called a page and is thesame size as sector on a hard disk. All this is done automatically bythe OS.
• One task the operating system has to carry out is the creating and managing of its file system on the hard disk.• There are many different ways this can be done, and the main of organising a system is using a filing system called FAT. FAT(File Allocation Table) is very useful for organising files and folders on the hard disk.• Another filing system is NTFS which is more common in modern computers running Windows XP, Windows Vista or Windows 7. NTFS has more advantages over the older FAT system due to it being more efficient and having an improved file security. But both use the same concept.• On every hard disk the data is stored in “Sectors”. Then Sectors are grouped together into “Clusters”.• A cluster is the smallest amount of storage a file can use, however if a file is smaller than a cluster the unused space is wasted. A cluster size on average is 4kb but can vary between 2kb to 32kb. Every cluster is numbered so that the FAT can locate each cluster on the hard disk.
• A Buffer is an area of memory in which is used to store data that is in the transition of being used and stored on a storage medium. An example of this would be if you were moving data from a digital camera to a printer. The data transfer speed between the devices will differ meaning that the main memory on the computer is used as a buffer, the speed of transfer is handled by the computer allowing data to be kept on the main memory as a buffer. The data enters the buffer at a significant speed allowing the camera to receive it at an appropriate sped then leaves to the printer at an appropriate speed. However data can not be removed at the same time as being added to the buffer. But to speed up the transfer, a process known as double buffering is used, this is when data is transferred from for example the camera into the first buffer, then at the same time any data kept in the other buffer is transferred to the printer. When buffer one is full and buffer two is empty the process is reversed, then this allows data to be entered to buffer two and the full buffer one can be emptied and transferred to the printer. This effectively increases the data transfer rate.
Whenever a new device is added to a computer such as a mobilephone, a printer, a scanner or any other USB device. A small pieceof software is installed windows comes preinstalled with therequired software for the device to communicate with thecomputer.This piece of software is called a “Driver”. The Driver is used astranslation software to convert the message the hardware sendsout and makes it so the Operating System can understand thedevice connected.For example; When you want to add a MP3 to your Mobile Phoneyou have you have the phones driver installed on your computerto enable the transfer of the MP3 track to the mobile phone.
CLICLI stands for Command Line Interface and is the most basicinterface you can get!CLI was mainly seen in the early days of computing and mostcomputers had simple technology inside of them, especially notadvanced enough to display colour on the screen and screenwere Black and White or Green and Black, and only a keyboardwas used it wasn’t until the GUI was created that a mouse wasintroduced.The best part about a CLI was it was quick if you knew thecommands it was quicker than a GUI. The most common CLI youprobably can think of is DOS(Disk Operating System).
GUIGUI stands for Graphical User Interface, the idea of having a GUI is that it is easy tounderstand and to use.However in 1981, workers in a company in America called Xerox Parc developed ahighly visual interface that involved all the same items we use today they are:• Windows• Icons• Menus• PointersOr in short WIMP. As soon as WIMP came on screen GUI’s have been used, eachdisplay was divided into areas called Windows. Any application you could see onscreen or a file that were represented by a small image are called Icons. A processcould happen by the user selecting it from a Menu. And what we used today as amouse we call it a Pointer.Over the years technology has evolved and we have improved displays betterthan 16 colours and 256 colours. Now we have millions of colours allowing theGUI to become the most user friendly display in the world!