1.5 Systems Software

• Operating Systems (OS)


  Software, which manages the hardware and software resources of a computer system and provides an interface for the user
• Kernel


  The heart of the operating system, responsible for looking after "the most low-level hardware operations"
• Multi-tasking


  The ability of an OS to supply the CPU with instructions from multiple programs in particular orders to create the illusion that a computer is processing programs simultaneously
• What do all OS's do?


  - Input data

  
  

  - Process that data

  
  

  - Output the result
• Utility software


  Used to maintain the computer system
• What are the types of user interfaces?


  - Graphical User Interface (GUI)

  
  

  - Command line interface

  
  

  - Menu driven interface

  
  

  - Natural language interface
• Graphical User Interface (GUI)


  - Windows, icons, menus, pointers (WIMP interface)

  
  

  - Visual

  
  

  - Interactive

  
  

  - Intuitive (ideal for beginners and average users)

  
  

  - Optimised for mouse and touch gesture
• Command line interface


  - Text based

  
  

  - Less resource heavy compared to GUI

  
  

  - More commands than GUI

  
  

  - Efficient

  
  

  - For advanced users

  
  

  - Useful for automating processes with scripts

  
  

  - This is often the interface that is used if you want to do something technical with your computer
• Menu driven interface


  - Mainly seen at cash points, pay at pumps machines in petrol stations and chip and pin devices

  
  

  - Consists of successive menus that are presented to the user

  
  

  - The user choses a single options at each stage

  
  

  - Often with buttons on a keypad although it can be touch input
• Natural language interface


  - Responds to questions in spoken language

  
  

  - Not always reliable

  
  

  - Getting better all the time

  
  

  - Seen on Alexa, Siri, Ok Google

  
  

  - Requires internet
• Fragmented


  Parts of memory that are split across RAM
• Multitasking


  - Running multiple applications at the same time by giving each application a small time-slice of processor time.

  
  

  - This allows more than one program to be held in memory at a time, and data shared between them such as copy and paste.

  
  

  - It also enabled you to listen to music on your PC at the same time as word processing.
• Memory management


  - When programs are loaded, the operating system decides where they are held in memory.

  
  

  - Over time the memory becomes fragmented as programs are loaded and closed because they use different amounts of memory.

  
  

  - The operating system must keep track of different program fragments

  
  

  - When the memory is full, the operating system uses virtual memory
• Device drivers


  - Translates operating system instructions into commands that the hardware will understand

  
  

  - Each peripheral needs a device driver

  
  

  - Many are already built into the operating system
• User management


  - The OS will provide multiple profiles/accounts for users

  
  

  - Users will have their own space with their own settings, folders and files

  
  

  - Users can choose to have a password protected account for added security

  
  

  - Users will have different access rights to certain folders and files. This means users can make certain files/folders private so that other users on the computer cannot see them

  
  

  - The OS will provide security for each user (Firewall, Anti-virus software etc.)

  
  

  - A client server network can use a fixed or roaming profile for a user, and manage login requests to the network
• File Management


  - Data is stored in files

  
  

  - Each file will have an application extension which allows the OS to determine what application it will open the file in

  
  

  - The OS provides a logical structure to store these files in a folder system

  
  

  - Users can search for, rename, duplicate, delete, edit, move, encrypt and organise their files in the file management system

  
  

  - Users can also choose default applications for these files to open in if there is more than one type of application

  
  

  - The folder system is located on secondary memory
• Encryption


  The process of encoding data before transmission so that if it were to be intercepted, it would be unreadable
• Utility software


  Software, which maintains a computer system by keeping it secure, organising data and optimising the system
• Formatting


  The act of preparing a disk for data storage
• Why do we use encryption?


  - To stop third parties from accessing data

  
  

  - So that if the data is intercepted or stolen it is still encrypted and secure as only the intended reader can unscramble it and understand the data

  
  

  - To decrypt the data, a special key is needed, a computer uses the key and a set of instructions to turn the data back into its original form

  
  

  - The strong forms of encryption that are used today are very difficult to crack, hackers can't use brute force attacks to guess the key
• How does compression make files smaller?


  - Compression software reduces the size of files by permanently or temporary removing data from them

  
  

  - Compressed files take up less disk space and are quicker to download

  
  

  - Standard file formats include .zip and .rar

  
  

  - Compressed files need to be extracted before they can be used
• What does defragmentation do?


  Puts files back into one block and collects the free space together
• What is defragmentation?


  - Reorganises files and application fragments in memory so that they are next to each other

  
  

  - Speeds up computer as a result
• Back-up software


  - A copy of data is stored either internally or externally (or both!)

  
  

  - Full backup - a full copy of memory is made at timed intervals

  
  

  - Incremental backup - only files and folders that were last used are updated
• What do formatting utilities do?


  - It creates sectors on which data can be stored

  
  

  - It creates a special list called the File Allocation Table (FAT)

  
  

  - The FAT is used to keep track of where data is located. Each time you write a new file to your hard disk, the table is updated with where the data is stored on memory
• Formatting utilities


  Prepare a storage device for data storage