Systems Software

Utility Software
1. Used for maintenance
2. Backup
  1. Making copies of data
    1. Used to restore data
    2. Stored externally
  2. Full backup
    1. A copy of everything is kept
    2. Slow processes
    3. Take up a lot of space
    4. Easy to restore
  3. Incremental backup
    1. Only changed files are saved
    2. Difficult to restore
      1. 1) Most recent full backup applied
      2. 2) Every incremental backup applied in order
3. Defragmentation
  1. Data reorganisation algorithm
    1. Improves performance
  2. Fragmentation
    1. files are split up when saved to secondary storage
    2. Files take longer to load
  3. SSDs
    1. Provide random access
      1. Fragmented data does not take long to load
    2. Can be damaged by defragmentation
4. Compression
  1. Reducing file size while preserving the contents
  2. Lossless compression
    1. Does not affect quality
    2. Used for documents and executable files
  3. Uses
    1. Backups and archives
    2. Network-based file transfer
  4. Lossy Compression
    1. Reduces quality
    2. Used for audio, video and images
  5. Takes a long time
5. Encryption
  1. Preventing unauthorised access
    1. Authorised parties are given a key
  2. 'Scrambling' data
    1. Uses specific algorithms
  3. Very mathematical processes
Operating Systems
1. Manages hardware access
2. Application Programming Interface (API)
  1. Code libraries
  2. Used by software developers
  3. Used to write applications for operating systems
3. Managers
  1. User interface manager
    1. Provides user interface
      1. Graphical User Interfaces (GUIs)
        Modern interface
        WIMP paradigm
        Windows
        Icons
        Menus
        Pointers
        Multi-touch
      2. Command-Line Interfaces (CLIs)
        Only displays text - no graphics
        Uses less memory than graphical
        Uses specific commands
    2. Allows users to control the computer
  2. Device manager
    1. Allocates resources to external hardware devices
      1. Which device is connected to which port
    2. Allows resources to be used by applications
    3. Allows applications to read/write data to devices
    4. Peripherals include
      1. Keyboard
      2. Printer
      3. Webcam
  3. Memory managers
    1. Controls memory used by applications
    2. If it fails, the computer can slow down or crash
    3. Allows for multitasking
  4. User manager
    1. Authenticates users
    2. Separates user accounts
    3. Single-user operating system
      1. Supports one user at a time
      2. Can support several accounts
    4. Multi-user operating systems
      1. Allows several users to be connected at a time
    5. Manages logged in users
  5. Process manager
    1. Controls CPU allocation between running applications
      1. CPU can only execute one process at a time
    2. Allows for multitasking
  6. File manager
    1. Controls files in secondary storage when:
      1. Read
      2. Written
      3. Opened
    2. Controls file locations
    3. Determines file types
    4. Manages access rights for files
Device drivers
1. Tells operating systems how to use hardware
  1. Contains software with instructions on how to:
    1. Understand data
    2. Format to expect data
2. Works with device manager

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	Created by Aaishah Ravat over 4 years ago