Systems Software

Systems Software

1. Utility Software

   • Used for maintenance
   • Backup
     • Making copies of data
       • Used to restore data
       • Stored externally
     • Full backup
       • A copy of everything is kept
       • Slow processes
       • Take up a lot of space
       • Easy to restore
     • Incremental backup
       • Only changed files are saved
       • Difficult to restore
         • 1) Most recent full backup applied
         • 2) Every incremental backup applied in order
   • Defragmentation
     • Data reorganisation algorithm
       • Improves performance
     • Fragmentation
       • files are split up when saved to secondary storage
       • Files take longer to load
     • SSDs
       • Provide random access
         • Fragmented data does not take long to load
       • Can be damaged by defragmentation
   • Compression
     • Reducing file size while preserving the contents
     • Lossless compression
       • Does not affect quality
       • Used for documents and executable files
     • Uses
       • Backups and archives
       • Network-based file transfer
     • Lossy Compression
       • Reduces quality
       • Used for audio, video and images
     • Takes a long time
   • Encryption
     • Preventing unauthorised access
       • Authorised parties are given a key
     • 'Scrambling' data
       • Uses specific algorithms
     • Very mathematical processes

2. Operating Systems

   • Manages hardware access
   • Application Programming Interface (API)
     • Code libraries
     • Used by software developers
     • Used to write applications for operating systems
   • Managers
     • User interface manager
       • Provides user interface
         • Graphical User Interfaces (GUIs)
           • Modern interface
           • WIMP paradigm
             • Windows
             • Icons
             • Menus
             • Pointers
           • Multi-touch
         • Command-Line Interfaces (CLIs)
           • Only displays text - no graphics
           • Uses less memory than graphical
           • Uses specific commands
       • Allows users to control the computer
     • Device manager
       • Allocates resources to external hardware devices
         • Which device is connected to which port
       • Allows resources to be used by applications
       • Allows applications to read/write data to devices
       • Peripherals include
         • Keyboard
         • Printer
         • Webcam
     • Memory managers
       • Controls memory used by applications
       • If it fails, the computer can slow down or crash
       • Allows for multitasking
     • User manager
       • Authenticates users
       • Separates user accounts
       • Single-user operating system
         • Supports one user at a time
         • Can support several accounts
       • Multi-user operating systems
         • Allows several users to be connected at a time
       • Manages logged in users
     • Process manager
       • Controls CPU allocation between running applications
         • CPU can only execute one process at a time
       • Allows for multitasking
     • File manager
       • Controls files in secondary storage when:
         • Read
         • Written
         • Opened
       • Controls file locations
       • Determines file types
       • Manages access rights for files

3. Device drivers

   • Tells operating systems how to use hardware
     • Contains software with instructions on how to:
       • Understand data
       • Format to expect data
   • Works with device manager