topic 6 - operating systems

• time slicing

  a short interval of time allotted to each program, so that they appear to multitask
• memory (RAM)

  • ensures that all programs and data are stored in the correct memory locations and don't corrupt each other
  • how the OS manages memory: allocates memory between different programs that are open at the same time
• software


  provides instructions to control the hardware components
• backup

  a copy of data that can be used if the original data is lost
• multitasking

  when a processor carries out small parts of multiple larger tasks in turn, very quickly
• systems software


  • manages the computer system
  • includes the operating system and utility software
• operating system (OS)

  • controls the computers hardware and software (allows applications to interact with the hardware on a device)
  • held in permanent storage and loaded into RAM when the computer is booted up
  • roles: security, (user) interface, interrupts, manages the CPU and RAM (memory), multitasking, peripherals and backing store
  • examples: microsoft window, android, apple ios and linux
• WIMP

  • windows
  • icons
  • menus
  • pointer
• security

  • ensures the system resources are protected from unauthorised access
  • how the OS manages security: allows users to log on, change passwords, create/delete accounts (with differing levels of admin and user rights) and looks for any new security updates to install
  • techniques to detect and remove malware: definitions, heuristics, sand boxing, quarantine and removal, firewalls and anti malware
• techniques to detect and remove malware

  • anti malware: observes for suspicious activity
  • definitions: scans for malware using a database of known malware definitions
  • signatures: analyses what a malware does and how to recognise it
  • heuristics: detects threats (not previously discovered) and identifies characteristics
  • sand boxing: where suspected malware is placed
  • quarantine and removal: allows the user to remove malware manually
• peripherals

  • a type of device that is able to transfer data to a computer and is not directly connected to the CPU
  • examples: keyboard, mouse and hard disk drive
  • how the OS manages peripherals: to communicate with and receive data input to an input device or send data output to an output device
• CPU

  • how the OS manages the CPU: allows different processes to utilise the CPU and not interfere with each other
  • how the OS manages multitasking: alternates between programs to make it appear that multiple tasks are running simultaneously (allowing efficient application execution), allocates time slices and manages tasks, so instructions can be executed by the CPU in turn
  • how the OS manages interrupts: the CPU prioritises interrupts based on importance, controls signals sent from hardware and software to the CPU when an app or device requires attention
• GUI

  • graphical user interface
  • allows the user to interact with a computer by using WIMP, through input devices
  • advantages: user friendly (uses WIMP) and is used without the need to learn the complicated commands
  • disadvantages: lot of processor power is needed, slow for experts, includes a large amount of graphics and therefore requires a higher capacity of secondary storage and RAM
• CLI

  • command line interface
  • allows the user to interact with the system by typing in specific commands
  • advantages: little memory (RAM) and processing power is needed (as it doesn't use graphics), experienced users prefer to use this (allows greater control) and doesn't use as much CPU processing time
  • disadvantages: can be very confusing for a novice (as commands have to be typed precisely) and a large number of commands need to be learned
• user interface

  • allows the user to interact with the OS using graphics and/or text
  • examples: CLI and GUI
  • how the OS manages interfaces: provides users with a graphical interface (WIMP), a user can have multiple windows open and switch between tasks (programs or windows), allows customisation, access to settings (hardware)
• file manager

  • helps the user to organise how they would like to manage their files on secondary storage devices (through a GUI)
  • how the OS manages the file manager: provides a GUI, allows the user to create, rename, move, copy and delete folders, create shortcuts and set permissions for access
• types of backing stores

  • full: copies anything identified as important, time consuming (as it uses a lot of system resources and demand on the processor) and a large amount of storage space needed to save all of the backups
  • incremental: only copies files that have been changed since the last full backup and the user can specify the location (cloud or external hard drive) and frequency of the backup
• device driver

  • software used to control the operation of a hardware device (printer, keyboard or mouse) that is part of a computer system
  • how the OS manages a device driver: allows a peripheral device to be connected to a computer and to be used by an operating system
  • how a device driver works: (1) a device is plugged into the computer, (2) the computer searches the operating system to see if it has the drive to run the hardware, (3) if a driver can't be found, it will load a generic device driver and (4) the driver is downloaded and installed
• backing stores

  • non volatile memory storage device that automates the process of backing up files (in the event of data loss, the file can be recovered to the point where it was last backed up)
  • examples: incremental and full
  • how the OS manages backing stores: maintains a record of the files stored on the backing store and the location of free space so that new files can be saved, organises files in a hierarchical directory structure and keeps a track of where the files are stored so they can be accessed when requested and transferred into main memory