managing resources

• Operating System


  • Manages hardware and software (resources) for a computer
  • Provides common services/user interface for computer programs
• Operating Systems


  • Mac OS
  • Ventura
  • Symbian
  • Linux
  • Android
  • Unix
  • Windows 11
• Booting up a computer


  1. BIOS

  2. Bootstrap loader

  3. Operating System

  
• Not all computers have operating systems (e.g. embedded computers like microwaves, fridges)
• Different operating systems are used on different types of devices
• Memory Management


  • Ensures programs/data do not corrupt each other
  • Ensures all programs and data is stored in correct memory locations
• Process Control


  • Ensures different processes can utilise the CPU and do not interfere with each other or crash
  • On a multitasking OS, ensures all tasks appear to run simultaneously
• Process


  An instance of a program being executed, containing the program code and any data it needs

  
• Managing Processes


  1. Operating System schedules processes' time on the CPU

  2. Each process is assigned a small block of time when the CPU will execute its instructions

  
• Processes with higher priority are run before other processes, which have to wait in a queue
• Minecraft requires a lot of processing so it has been given higher priority than other processes
• Virtual Memory


  • Memory is split into chunks and each process is given some of those chunks
  • Extra pages are stored on secondary storage (backing store) when there is not enough memory
• Security Control


  • OS allows users to create, manage and delete accounts with different permissions
  • Allows multiple users to log on and change passwords
• Managing Backup Space


  • Ensures data is stored and can be retrieved correctly from any disk drive
  • Creates and maintains a filing system (FAT or NTFS)
  • Organises files in a hierarchical directory structure
• User Interface


  Allows a human to interact with the computer system
• Disk Defragmentation


  • Data written to hard disks in blocks can become fragmented over time
  • Disk defragmentation physically re-arranges the files to improve access speed
• File Compression


  • Software-based compression slows down disk access, hardware-based compression does not
  • Compression is always lossless
• Examples of how the operating system provides a user interface

  • Allows copying/deleting/moving/sorting/searching of file or folders
  • Allows access to system settings such as hardware
  • Provides a command line interface
  • Allows users to have more than one window open
  • Provides a graphical user interface (windows, icons, menus, cursors)
  • Provides user with errors/help messages
  • Allows for customising the interface e.g., changing background/desktop setting
  • Allows user to switch between tasks (programs/windows)

  
• The operating system manages the following resources: peripherals, printing, backing store, file compression, disk defragmentation, main memory, processes, and security

  
• Human Computer Interface (HCI)


  The way in which people and computer systems interact
• An interface is required to allow a person and a computer system to communicate
• Interfaces provided by the operating system can be identified by the style of communication they use

  
• Some interfaces are entirely text-based, whereas others use images to represent different commands
• Graphical User Interface (GUI)


  • Allows users to interact with a computer system through graphical icons
  • Introduced to help users, especially beginners, to use a computer system as Command Line Interfaces (CLIs) were found to be difficult to use

  
• Features of a graphical user interface


  • Windows
  • Icons
  • Menus
  • Pointers/Cursors
  • Assistants/help files/tutorials
  • Favourite settings/change environment/customisation
  • Shortcuts/hot keys
  • Task bar/ribbon bar/tabs/customised toolbar

  
• Command Line Interface (CLI)


  An entirely text-based interface that allows a user to communicate with a computer system by typing in commands

  
• Before graphical user interfaces (GUIs) were developed, command line interfaces were the most widely used interface
• Touch Sensitive Interface (TSI)


  Commands are issued, or data is input, by touching the screen with your finger or a stylus pen
• Touch sensitive screens can interpret actions made by the user, such as pinching and swiping

  
• Menu driven interface


  Allows people to interact with a computer system by presenting the user with and allowing them to work through a series of menus
• Menu driven interface examples


  • The original iPod Classic
  • Menu bars
• Utility software


  System maintenance tools included with operating systems that allow users to maintain the upkeep of their computer systems
• Biometrics


  Body measurements and calculations related to human physical characteristics and behaviours
• Utility programs


  • Disk defragmentation
  • Compression
  • Virus scanning
  • System monitoring
  • System backup
  • Disk scanning and repair
  • Task management
  • Firewall
• Disk defragmentation


  • Files are split and stored on different parts of the disk, slowing down loading
  • Defragmentation physically re-arranges files so parts are stored together, improving access speed
• Modern computer systems use biometric input to identify and validate system users
• Compression


  Software program that can compress and decompress various file types to reduce file size for storage
• The first use of a biometric system on a portable device was fingerprint scanning on the Pantech GI 100 mobile phone in 2004
• Apple have used facial recognition via the camera and thousands of spots along the user's face to identify the user's facial patterns
• Some advanced viruses attempt to evade virus protection software by changing their own code so they no longer match the "signature" in the virus signature database. These are known as polymorphic viruses.