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Operating Systems

Operating Systems. AQA Computing: A2 COMP3. Role of an operating system. 4.1. What is an OS?. Extremely complex piece of software Provides an interface between the hardware and the users Hides complexities of the hardware Mange hardware resources

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Operating Systems

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  1. Operating Systems AQA Computing: A2 COMP3

  2. Role of an operating system 4.1

  3. What is an OS? • Extremely complex piece of software • Provides an interface between the hardware and the users • Hides complexities of the hardware • Mange hardware resources • Control processors, memory, I/O devices, manage data storage

  4. Software • System Program: a program that manages the operation of a computer • Operating System: the most fundamental of all system program’s

  5. Resource Management • A satisfactory performance is desired. This is managed and achieved via the OS system programs • Number of jobs to be completed / response time required

  6. Resource Management System Program’s can be classified according to the resources they mange

  7. Processor scheduling

  8. Memory management Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed.

  9. I/O management

  10. File management

  11. Operating system difficulties • Developers have to keep the OS flexible enough to run hardware from different manufacturers • Printers, disk drives, various peripherals

  12. Virtual Machine • Hiding the details of the hardware is achieved with the virtual machine • Layers of system software are placed on the hardware

  13. Virtual Machine

  14. Application Programming Interface (API) • Developers can write software and have confidence that it will run on another computer • Hardware upgrades • Example: • Java • Scanner sc = we Scanner(System.in); • sc.next();

  15. User Interface Part of the virtual machine that provides interface that the user can interact with • CLI • Command Line Interface • GUI • Graphical User Interface

  16. CLI • User types in prompts and commands followed by return key • Return key submits command • MS-DOS

  17. GUI • An interface built up of windows • One window has the focus at any given time • Event driven

  18. Operating system classification 4.2

  19. Interactive operating system • User interacts directly with the system • Commands are supplied, executed and returned to user • Direct two way communication

  20. Real-time operating system • RTOS • Inputs processed in a timely manner • Time critical processes • Airline reservation system • Aircraft control system • Deadlocks

  21. Network operating system • Novell NetWare • Layer of software added to the operating system connected to the network • Network layer intercepts commands that reference resources elsewhere on the network • C: D: local drives • N: P: network drives

  22. device • Any computer device that has an operating system • Can change the devices function by changing the code of the OS • Modern OS – code is layered or modular. Easily updatable. • NOT all computers have OS’s • Washing machine

  23. Operating systems allow: • Device can multitask • Can operate in real-time • Hardware can be changed • New applications added easily • Basic functionality changed by updates to OS codeinstead of hardware

  24. Smartphones • Interest in smartphones has led to OS being developed for them • They run complete OS’s • Sandbox: a tightly controlled set of resources for guest programs to run in

  25. Embedded computer systems • OS embedded within other machinery • Limited or no user interface • Cars, telephones, appliances • Cars have 12 or more embedded computer systems • Dedicated purpose

  26. Embedded computer system

  27. Embedded computer system • Embedded systems have additional upper-layer software components • TCP/IP, FTP, HTTP, HTTS • Audio and video capabilities (drivers and codecs included)

  28. Desktop operating system • All desktop computers have OS’s • Windows • Linux • MAC • Must support a range of general purpose tasks • Very sophisticated • Hardware • Software • Processors • Memory • Real time requirements • Network protocols

  29. Desktop operating systems • Written in layers • Easily updatable • Eg. Security updates • Sophisticated GUI’s

  30. Server operating system • OS optimised to provide one or more specialised services to networked clients. • File storage • Domain control • Running applications • Optimised for the service they carry out • Performance would not be achieved if it had to do general purpose processing

  31. Operating system questions Text book questions

  32. Questions • Computer software is divided into two categories. Name them. • What is the role of an OS? • What are the four key resources managed by an OS? • What is a virtual machine? • What is an API? • Why it is important that an OS has a standard API? • Name two types of OS. • How do OS for embedded systems differ from OS for general purpose computers? • Give three computer-operated devices found in a home that do not require an operating system. • Explain why the OS for a mobile phone will be very different from the OS for a desktop computer. • Explain the meaning of an embedded computer system for a car. • Why have OS’s for embedded computers had to become more sophisticated.

  33. Exam question answers • http://store.aqa.org.uk/qual/gce/pdf/AQA-COMP1-W-MS-JUN10.PDF

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