Operating Systems

Without an operating system your computer would be useless! A computer contains an Operating System on its Hard Drive. This is loaded after the computers boot up sequence, and allows the user to use the keyboard and mouse to be able to store data to a hard disk drive You can find operating systems in Personal Computers, Sat Navigation Systems, Network Servers, Mobile Phones, Game Consoles and even CARS!

Operating Systems The main function of a Operating System are: Processor Management Memory Management Device Management Storage Management User Interface

Processor Management If you’re a user who has many different applications open or maybe you might be just browsing the internet and have lots of different tabs open. For the computer to be able to switch between these applications or to switch between the tabs the Operating System has to switch between different processes thousands of times a second.

Virtual Memory RAM has a limit, however your operating system may need more primary memory than there physically is, therefore the computer uses virtual memory. A good example is if a computer has 2GB of RAM as primary memory, however it could have up to 4GB of Virtual Memory. This works by the operating system setting aside part of its secondary storage on a storage medium e.g. hard disk/memory stick to be used as temporary memory store. This area is know as the temporary memory store and is called a page file or a swap file. The operating system will use this page file once all the available RAM has been used up in our instance if the 2GB of RAM is used up then the OS will start to store chunks of the memory on the secondary storage. The chunk itself is called a page and is the same size as sector on a hard disk. All this is done automatically by the OS.

File Allocation Table (FAT) 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.

File Allocation Table (FAT)

Buffer 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.

Device Driver Whenever a new device is added to a computer such as a mobile phone, a printer, a scanner or any other USB device. A small piece of software is installed windows comes preinstalled with the required software for the device to communicate with the computer. This piece of software is called a “Driver”. The Driver is used as translation software to convert the message the hardware sends out and makes it so the Operating System can understand the device connected. For example; When you want to add a MP3 to your Mobile Phone you have you have the phones driver installed on your computer to enable the transfer of the MP3 track to the mobile phone.

CLI(Command Line Interface) & GUI(Graphic User Interface) CLI CLI stands for Command Line Interface and is the most basic interface you can get! CLI was mainly seen in the early days of computing and most computers had simple technology inside of them, especially not advanced enough to display colour on the screen and screen were Black and White or Green and Black, and only a keyboard was used it wasn’t until the GUI was created that a mouse was introduced. The best part about a CLI was it was quick if you knew the commands it was quicker than a GUI. The most common CLI you probably can think of is DOS(Disk Operating System).

CLI(Command Line Interface) & GUI(Graphic User Interface)

GUI GUI stands for Graphical User Interface, the idea of having a GUI is that it is easy to understand and to use. However in 1981, workers in a company in America called Xerox Parc developed a highly visual interface that involved all the same items we use today they are: Windows Icons Menus Pointers Or in short WIMP. As soon as WIMP came on screen GUI’s have been used, each display was divided into areas called Windows. Any application you could see on screen or a file that were represented by a small image are called Icons. A process could happen by the user selecting it from a Menu. And what we used today as a mouse we call it a Pointer. Over the years technology has evolved and we have improved displays better than 16 colours and 256 colours. Now we have millions of colours allowing the GUI to become the most user friendly display in the world!

CLI(Command Line Interface) & GUI(Graphic User Interface)