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1.5 Systems software - Coggle Diagram

- - - - Uses an algorithm to convert plain text into cipher text
      - Makes it difficult to be understood by a human or machine without knowing how to decrypt it
      - Encryption utility software is responsibly for applying encryption algorithms and decrypting using a key
      - Data is encrypted for transferring data securely across a network to prevent it from being understood if intercepted
      - Can be used on files stored on secondary storage to prevent access to files in case of hacking
    - - Software that looks at all the data on a hard drive and reorganises it so related data is stored together
      - To start off, everything is saved together
      - As files are deleted and new files are added your computer will save data in the first available space
      - If that space is too small for all the data needed for the file, the available space is used up first and the remaining data is saved elsewhere on the hard drive
      - Disk Fragmentation can slow down performance
      - If related data becomes separated, the hard drive's read/write heads need to move to different areas of the disk in order to retrieve or save files
      - Defragmentation software follows the following proccess:
        
        Moving files to a temporary 'scratch' space on the hard drive
        
        Collecting together the empty spaces
        
        Collecting together the related data
        
        Replacing the data so that related data is now store sequentially
      - Once data is stored together, the read/write head preforms the task of retrieving or saving data in less time
      - Many OS automatically preform disk defragmentation without user involvement
      - SSDs don't require disk defragmentation as SSDs read blocks of data that are fragmented as quickly as they read data stored sequentially
    - - Responsible for compressing and decompressing files saved
      - Reduces amount of data inside files
        
        Saves space on secondary storage devices
        
        Reduces transmission time when sending files across a network
        
        Compressing files helps keep files within the maximum attachment limit if you want to send a file
- - - - Allows user to interact with the computer
      - Types of user interfaces
        
        Command line interface (CLI)
        
        User interacts with system by typing commands executed by the system
        
        No graphics or icons
        
        Requires little secondary storage and RAM
        
        Provides greater control over computer system with no restrictions
        
        More difficult to use
        
        Graphical user interface (GUI)
        
        Most common form of operating system
        
        Found in desktops, smartphones and Sat Nav
        
        Typically made up of
        
        Windows
        
        Icons
        
        Menus
        
        Pointers
        
        User-friendly interface - visual and very intuitive
        
        Requires more secondary storage capacity and RAM
        
        Natural language interface
        
        User gives instructions for the computer to preform using language you would use while speaking to people
        
        Can be text based
        
        Can be used with audio commands ('turn on the lights')
        
        Cannot easily interpret certain commands and tasks
        
        Often rely on internet to process commands on a remote server
    - - Instructions and data needed for a process have to be availbale in main memory
      - The OS runs a memory manager program which:
        
        Keep track of what portions of memory have been allocated
        
        Maps memory to each process
        
        Determines how much memory to allocate to each process
        
        Determines when a portion of memory should be available for a process
    - - Device driver is a program that controls the operation of specific types of devices (keyboard, mouse, headphones)
      - Device drivers provide an interface that allows the OS to interact with the device
      - Allows devices to interact with software on computer
      - Installing device drivers
        
        Usually installing using software built into the OS
        
        Older systems require installation of device drivers from physical storage media (CD's)
        
        If a specific device driver cannot be found - OS loads a generic driver
        
        Generic driver may be missing features that the device driver would provide
        
        Operation of generic device driver may be inefficient, slowing down preformance
    - - OS supports security of device by ensuring system resources are protected from unauthorised access
      - OS systems allow users to create accounts so only authorised users can access the system
      - Users with admin rights can allocate other users specific permissions
        
        Which files they are able to access and modify
        
        Ability to add new users or to install or uninstall software
    - - Able to preform tasks on files and folders such as
        
        Creating
        
        Renaming
        
        Moving
        
        Deleting
      - Help user organise their files
      - Backing storage management
        
        Refers to any Non-volatile memory storage device
        
        OS keeps a directory of where files and programs are stored
        
        Files and programs can be accessed quickly when requested and transferred into RAM
        
        Speeds up storage and saves computational resources
        
        Don't have to search for free space every time a user wants to save a file
    - - OS uses a scheduler to swap tasks in and out of the processor
      - Makes it appear to the user as the computer is carrying out more than one task at the same time
      - Listening to music while doing homework