Types of Operating System

• Distributed operating system


  A form of parallel processing system which speeds the load over multiple computer servers
• Distributed operating system


  1. A single job is set up into several banks

  2. Each of these is run on a separate computer

  3. Coordinated by the operating system

  4. Appears to the user as a single system
• Distributed operating systems


  • Intranets
  • Cluster of servers that share memory and tasks
• Distributed operating systems


  • Linux
  • Unix
  • Windows
• Multi-tasking operating system


  Runs on a standalone computer

  Can run many jobs simultaneously

  Switches between them so each appears to be the only one running
• Multi-tasking operating system


  • Windows
• Multi-tasking operating system


  1. You may be playing music

  2. Running a Python or VB program

  3. Checking your emails
• At any one time, the Task Manager will probably find several programs in memory, most of which are not currently executing
• Multi-user, multi-tasking system


  Time-sharing systems are multi-user, multi-tasking systems where a single powerful supercomputer is connected to dozens or hundreds of terminals, and each user gets a slice of processor time according to a scheduling algorithm
• Operating systems used by mobile phones

  • Combine the features of a personal computer operating system with their own special features useful for mobile use such as managing cellular and wireless connectivity as well as phone access
  • Typically, smartphones respond to the user's touch - the user can tap on the screen to open a program, pinch their fingers together to minimise or enlarge a screen, or swipe across the screen to change pages
  • They also have features useful for mobile systems such as GPS mobile navigation, camera, video camera, speech recognition, music player
• Most mobile operating systems are tied to specific hardware
• Smartphones have two operating systems


  The main system operating the user interface and running the application software, and a second, low-level proprietary real-time operating system which operates the radio and other hardware
• These low-level systems have a range of security vulnerabilities permitting others to gain control over a mobile device
• Embedded operating systems


  Operating systems found in all kinds of hardware from a washing machine or microwave oven, to the control system of a passenger aircraft or a space shuttle
• Embedded operating systems


  • Minimal user interface, probably consisting of a few buttons or a dial and maybe a small screen
  • Accept input from sensors, and send output to control devices
  • Limited amount of RAM so a complex memory management system is not required
  • No permanent data storage devices to be managed
• Real-time operating system


  Operating system in the flight-control system of a "fly-by-wire" airliner such as the Airbus 320
• Real-time, embedded operating system


  • Must respond very quickly to any inputs or sensors
  • Must be able to deal with many inputs simultaneously
  • Must have "failsafe" mechanisms designed to detect and take appropriate action if a hardware component fails
  • Must incorporate redundancy - that is, if one component fails, it must automatically switch to backup hardware
• BIOS (Basic Input Output System)

  The program stored in EPROM (Erasable Programmable Read-Only Memory) that gets your computer started after you turn it on
• BIOS


  • Intakes and tests the peripheral hardware components
  • Loads the operating system for the key parts of it from the hard disk into RAM
• BIOS


  Historically provided an abstraction layer which allowed a consistent way for application programs and the operating system to interact with input-output devices
• In more modern computers BIOS is not used after loading the operating system
• Device driver


  A computer program that provides a software interface to a particular hardware device
• Device drivers


  • Enable operating systems to access hardware functions without needing to know the details of the hardware being used
  • When you attach a new printer to your computer, you will need to install the device driver program that comes with it before it will work
  • Sometimes the OS will do this automatically if it detects that the printer is one for which it already has a driver
• Device drivers


  • Are hardware dependent and operating system specific
  • Communicate with the device via the system bus or communications subsystem to which the hardware connects
  • When a calling program invokes a routine in the driver, the driver issues commands to the device
  • Once the device sends data back to the driver, the driver may invoke routines in the original calling program
• Virtual machine


  Any instance where software is used to take on the function of the machine, including executing intermediate code or running an operating system within another to emulate different hardware