Operating Systems

• Operating System examples


  Microsoft:

  • MS-DOS
  • Windows

  Google

  • Android
  • Chrome OS

  Apple

  • macOS

  Linus Torvalds

  • Linux
• Operating Systems 


  manage computer hardware, users and the resources used by software
• Operating Systems responsible for managing:

  user interface

  memory management

  multitasking

  peripheral management and drivers

  user management

  file management
• User Interfaces


  provide a method for users to interact with a computer
• Example of User Interface


  graphical user interface (GUI)

  Menu-driven interface

  Command Line Interface (CLI)

  Voice Activated

  Real-time
• Graphical User Interfaces - Desktop interfaces

  pointers

  windows

  menus

  icons

  drag and drop
• Graphical User Interfaces - Smartphone and touch interfaces

  no pointers in general as they cannot be seen under finger

  windows (for app) generally take up full screen
• Command Line Interfaces


  text commands are entered into the computer

  Faster to enter commands than using mouse for expert users who know the commands
• Advantages of Command Line Interfaces

  requires very little processing and save need for expensive graphics card

  requires much less hard disk storage space

  requires less RAM
• Menu-driven interfaces

  Menu driven interfaces are often used by devices that have a dedicated function including MP3 players, ATM machines and self service checkouts
• Memory Management


  to run a program the computer must copy the program from storage into main memory
• Reason for memory management

  data used by program is copied into main memory

  operating system keeps a record of where each program and its data are located

  operating system will make sure not to overwrite existing programs and data
• Multi-tasking


  where an operating system manages many tasks happening at the same time
• How Multitasking works 


  example of multitasking: having web browser open whilst playing music and messaging friends

  many other background process also are running

  the operating system decides which process will next run on the CPU and for how long
• Peripheral Management


  operating system getting inputs and sending outputs to peripheral devices
• Examples of Peripheral devices


  mice

  keyboard

  printers

  displays

  digital cameras

  graphics tabelts
• Device Driver


  a program that controls peripheral devices such as printers mice and displays
• What device drivers do

  each device communicates with the operating system via its own driver

  many device drivers come with an operating system but a brand new type of device will be supplied with a driver which needs to be installed
• Disk and file Management

  hard disk in a computer is a storage peripheral
• What the operating system does for file management


  manages where on the disk files are written

  keeps track of where they are so they can be retrieved

  makes sure no file overwrites another file
• File management 


  carried out by operating system
• Features of File Management

  naming files

  allocating files to folders

  moving files

  saving files

  copying files

  deleting files
• User Management

  operating system is responsible for user logins and passwords

  it will store all users and their passwords in a file or database
• Access Rights


  if a computer is used by more than one person, each user should be able to see only their own files

  users and system administrators have different levels of access rights

  some users may be allowed to read files but not edit them