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2013-05-21 04:00:45

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  1. What is an Operating System?
    • This is a collection of software that
    • managers computer hardware resources and provides common services for computer
    • programs

    • *Time sharing Oss schedule tasks for
    • efficient use of the system, allocation of processor time, mass storage etc*

    • *Acts as intermediary between hardware and
    • programs*
  2. Types of OSs


    Multi Task


  3. Real-Time
    • Multi tasking Os that aims to execute
    • real-time apps, using specialised scheduling algorithms so that they can
    • achieve a deterministic nature of behaviour.

    • *They have an event driven or time sharing
    • design*
  4. Objectives of real time OSs
    Quick and predictable response to events.
  5. What is event driven design?
    • Switches between tasks based on their
    • priority or external events
  6. What is time sharing design?
    Switches tasks based on clock interrupts.
  7. Multi-User OS
    • Allows multiple users to log on
    • concurrently
  8. Examples of Multi-User OS
    Time sharing systems

  9. Multi Task OS
    • Allows more than one program to run at a
    • time.
  10. Examples of Multi-tasking OS
    Windows OS, MAC OSX, Linux
  11. Types of multi-tasking

  12. How pre-emptive types of OS work
    • OS slices CPU time and allocates one slot
    • to each program.

  13. How cooperative types of OS work
    • Processes give time to other processes in
    • determine manner.
  14. Distributed OS
    Manages a group of independent unified computer
  15. Embedded OS
    • Designed to be used in embedded computer
    • systems.

    • *operate in small machine like PDAs, work
    • with minimal resource. E.g. Windows CE and Minix 3*
  16. Examples of OSs

    MAC OS X





    IBM Z/OS
  17. What is Kernel?
    • Hub of an OS that acts as a bridge between
    • application and actual data processing at the hardware level.
  18. How the Kernel works
    • Allocates time and memory to programs,
    • handles file storage and communication in response to system calls.

    • It enables programs to execute, handles
    • events generated by system (software) calls and interrupts (Hardware). It also
    • manages access to resources.
  19. System calls are initiated by?
    • User level programs, like opening files and
    • starting programs.
  20. What is shell?
    • Software that provides and interface for
    • users of an OS to access the services of the kernel.
  21. How the shell works
    Acts as interface between user and kernel

    It’s a CLI

    • Interprets commands and arranges for their
    • carrying out

    • Allows programs to be started and give them
    • session specific arguments

    • Allows trivial operations on local storage
    • like listing directory contents, moving and copying file across the system.
  22. Functions of OSs
    Program execution

    I/O operations

    File system management


    Error detection
  23. Program execution
    • Provides convenient environment for the
    • user to execute programs, without worrying about complex tasks like allocating
    • and de-allocating memory.
  24. I/O operations
    • Carries out underlying I/O operations on
    • behalf of the user
  25. File system management
    • Frees the user from complex tasks by
    • manipulating files in I/O operations and managing secondary storage.
  26. Communication
    • Exchanging information between processes on
    • different computer systems
  27. Error detection
    • Frees the user from worrying about system
    • errors propagating and causing system malfunctions by monitoring the system for
    • errors
  28. OS components
    Process management

    Main/primary memory management

    File management

    I/O system management

    Secondary-Storage management


    Protection system
  29. Process management (Components of OS)
    Manages multiple user and system process. E.g. printer spooler, name servers, files servers etc
  30. What is a process?
    One instant of a program in execution
  31. What does a process consist of?
    • Includes the complete execution context
    • (Code, data, PC registers, OS resources in use)
  32. Five major activities of OS in process management
    • Creation and deletion of system and user
    • processes

    Suspension and resumption of processes

    A mechanism for process synchronisation

    A mechanism for process communication

    A mechanism for deadlock handling
  33. What is main/primary memory management(OS COMPONENTS?)
    Array of words or bytes

    • *allocates and deallocates memory, loads
    • processes and keeps track of memory in use.
  34. Major activities in memory management
    Keep track of memory in use and by whom

    Load processes when memory space becomes available

    • Allocates and deallocates memory space as
    • needed.
  35. File management
    • Stores files in secondary disks for long
    • term storage
  36. What is a file?
    • A file is a collection of related
    • information as defined by the user
  37. Main activities of OS in file management
    Creation and deletion of files

    Creation and deletion of directories

    Mapping files in secondary storage

    • Back up of data on stable storage
    • devices/media

    • Support for primitives for manipulating
    • files and directories
  38. I/O system management
    • Manages specific hardware on behalf of the
    • user
  39. What are primitives?
    • Basic interface or segment of code that can
    • be used to build more sophisticated program elements or interfaces.
  40. Secondary storage management
    • Manages free space, allocates storage space
    • and schedules requests for memory accesses
  41. Address spaces are?
    Locations on storage
  42. Three major activities of OS in secondary storage management
    • Managing free space available on secondary
    • device

    • Allocation of storage space when new file
    • have been written

    Scheduling requests for memory access
  43. Networking (OS components)
    • Manages a collection of processors that do
    • not share memory, clock or peripheral devices in a distributed system, through
    • communication lines called networks
  44. Protection system (OS components)
    • Mechanism for controlling the access of
    • programs, processes or users to resources defined by the computer system.
  45. Command interpreter system
    • An interface of OS with user, which allows
    • the user to execute programs through commands.
  46. Function of a command interpreter system
    • Gets and executes the next user specified
    • command
  47. Advantages to separating command interpreter from kernel
    • Ability to change the way the CI looks.
    • Which can not be done in kernel

    • To prevent malicious processes that gain
    • access to certain parts of the kernel from gaining access to the CI
  48. What is a graphic user interface?
    • Is a type of interface that allows the user
    • to interact with an electronic device using images (icons) rather than text.

    • *used in hand-helds, gaming devices, mp3
    • players*
  49. How does a graphic user interface work?
    • Uses graphical representation of
    • information and actions available to the user, plus visual indicators such as
    • secondary notations as opposed to text based interfaces that use typed command
    • label or text navigation
  50. What is a command line interface?
    • Form of interaction with a computer
    • system/program were a user issues commands in form of command line
  51. OS CLI
    • Distinct programs supplied with the OS.
    • That use text interfaces called, CLI, Command processor or shell
  52. What is shell in principle?
    • Any program that constitutes a user
    • interface. Including graphical ones like EXPLORER.EXE
  53. Usage of CLIs
    Fast entry of text over pure GUI

    • Systems with insufficient resources to
    • support GUI

    • Often used by programmers, techs system
    • admins in engineering and scientific environment. Also people with visual
    • disabilities.
  54. OS requirements
    • System requirement: hardware and software
    • components needed for the OS to run efficiently
  55. Types of system requirement

  56. What are recommended system requirement?
    • Recommended by manufacturers, often
    • significantly higher than requirements needed to run system. *better guidelines
    • than minimal in order to have a fully usable and enjoyable experience with the
    • software.
  57. What are hardware requirements
    Physical computer resources required to run a computer program/software efficiently
  58. Hardware compatibility list (HCL)
    • List of tested, comparable sometimes
    • incompatible hardware devices for the particular OS
  59. Computer architecture is?
    • Structure, behaviour and design of
    • computers

    *OSs are designed for particular computer architecture*
  60. Processing power (Hardware requirements)
    Processing power is a measurement of how powerful this chip is, i.e. how fast it can do the required calculations. Is fundamental to efficient running of OS
  61. Memory (Hardware requirements)
    • RAM and how it’s used is considered when
    • defining requirements.
  62. How is secondary storage vital to OS components
    • HDD requirements vary depending on size of
    • software
  63. Display adapters (Hardware requirements)
    • Software requiring a better than average
    • computer graphics display, like graphic editors and high end games display
    • adapters in system requirements
  64. Peripherals (Hardware requirements)
    • Some software needs extensive use of dome
    • peripherals demand higher functionality.
  65. What are minimum system requirement?
    These are the minimum requirements for basic functionality
  66. 3 major types of application CLIs
    • Parameters
    • Interactive command line sessions
    • OS inter-process communication