GoConqr hat ein neues Design! Sag uns, wie es dir gefällt.

Kostenlos registrieren

Karteikarten

SLR 4 - Operating Systems / Systems Software

Kyle Clinch Computing AS level Englisch 41 Karten

Karten in diesem Stapel (41)

  1. 1Purpose of Operating SystemsGives a User Interface
    Allocates and manages memory use
    Uses device drivers to to communicate with devices
    Controls the processor
    Uses protocols to communicate with other machines and devices
    Secures the computer, preventing unauthorised access
    Provides a framework for applications to run
  2. 2Layers of the ComputerLayers of the computer are only concerned with the layer above them, and it goes in the following order: User>Application>Operating System>Hardware
  3. 3Examples of Operating SystemsMicrosoft Windows
    Apple IOS
    Google Android
    Unix Linux
  4. 4PagingProcesses and memory spaces divided into equal size 'pages'. Doesn't take into account the contents of the page so some programs may not function properly. Pages can be easily slotted in and out of the RAM.
  5. 5SegmentationProcesses are divided logically, making sure that the contents of the segment still work when executed. Segments are different sizes, and may be harder to fit into gaps due to differing sizes.
  6. 6Virtual MemoryUsed when RAM is full. Instructions not being used are moved to a reserved area of hard disk and then swapped back in when needed, like running programs which are not currently being used. When there is enough space, it is moved back again, and programs slow down when in Virtual Memory.
  7. 7Drawbacks of Virtual MemoryMay take more time to move instructions than executing them
    Disk thrashing - things keep being swapped in and out repeatedly
    Makes computer slow as virtual memory is slower than RAM
    CPU can only execute instructions in the RAM, so when they're needed they have to be moved from virtual memory which is slow
  8. 8InterruptsDevice sends a signal if it needs attention and the computer deals with it
  9. 9PollingChecks with each device individually if it needs attention. This is inefficient as most devices don't need to be checked 24/7
  10. 10Fetch-Decode-Execute InterruptsAt the end of the cycle, the CPU will check for interrupts and if there are any, it will stop what it is doing and carry it out, storing where it left off.
  11. 11Interrupt Service RoutineA routine which responds to an interrupt. It examines the interrupt and decides how to handle it.
  12. 12Storing ProcessesInterrupts are pushed onto the stack and executed before any other processes can start. Interrupts with higher priority can interrupt other interrupts.
  13. 13Types of InterruptHardware Interrupts
    Software Interrupts
    Input/Output Interrupts
  14. 14Hardware InterruptsPower button is pressed
    Memory parity error
  15. 15Software InterruptsIllegal instruction encountered
    Arithmetic overflow
    New logon request
  16. 16Input/Output interruptsBuffer nearly empty
    Signal the complete of a data transfer
  17. 17SchedulingManages which process needs to be executed next, by giving each process a slice of time which it can execute for. Processes are stored in queue so each process takes its turn, and processes may be blocked in they need to wait for an input or an output. This gives the illusion of multiple processes running at the same time.
  18. 18First Come First ServeFIFO (First in first out)
    First one in the queue is executed, and they are served in the order they arrived.
  19. 19Shortest Job FirstThe process with the shortest process time goes first and executes fully without stopping.
  20. 20Round RobinThe process are all given an equal slice of time they can execute for, then they stop and let the next process have its turn. If they do not finish executing they return to the queue.
  21. 21Shortest Remaining TimeSimilar to Shortest Job First but it allows for processes to be suspended if a smaller process arrives. If a process with a shorter time arrives the currently running one is suspended.
  22. 22Blocking ProcessesIf processes need an input or output they are blocked. It joins the queue again once it has received its input.
  23. 23Multilevel Feedback QueuesThere may be multiple queues which may have different priorities and algorithms, and algorithms can move processes from queue to queue as needed.
  24. 24PreemptiveAllows a process to be interrupted by a high priority process.
  25. 25Non-PreemptiveDoesn't allow a process to be interrupted by a high priority process.
  26. 26Multi-Tasking Operating SystemsWhen one processor can run different processes at nearly the same time using scheduling. Allows for multiple applications to be running at once.
  27. 27Multi-User Operating SystemsThere may be different users on one computer with different preferences and permissions. Designed for the sharing of resources like files and programs.
  28. 28Distributed Computing Operating SystemsOperating system coordinates computers across a network like they were a single system. Different devices can do things at the same time.
  29. 29Embedded Operating SystemsHighly specialised for a single purpose. Small computers designed to fit into a machine or appliance.
  30. 30Real-Time Operating SystemsIn a safety critical environment where there cannot be any delays. Used when processes need to be executed within a time frame. Lots of redundancy in the system deliberately so that when the system needs it in an emergency there is processing power to spare.
  31. 31BIOSBasic Input Output System
    The BIOS is ROM, fast to read and non-volatile. Carries out instructions used to start the computer when it is turned on.
  32. 32CMOSComplementary Metal Oxide Semiconductor
    Stores the BIOS.
  33. 33POSTPower On teST
    When the computer is turned on the BIOS starts a POST to test if all the hardware is present and working properly. It then uses this data to start the computer or show a warning message. Prevents the BIOS from crashing if needed hardware is missing.
  34. 34BootstrapA program which runs after the POST. Loads the OS Kernel into the memory and hands control over to it.
  35. 35OS KernelCentral part of the OS. A small program which allows the OS to have complete control over the computer. After the Bootstrap, the OS Kernel loads all the needed programs into memory.
  36. 36Dual BIOSMost modern Computers have two BIOS'. A main one carries out the instructions used to start the computer and a second to restore the main BIOS if it fails, for example if it is corrupted or crashes.
  37. 37Device DriverSoftware that tells the OS how to communicate with a device. The driver translates the instructions from the OS so that the device can understand. Often installs automatically when a device is plugged in.
  38. 38Virtual MachineA digital program which has the same functionality as a physical device. Programs ran on a virtual machine do not know it is on one.
  39. 39EmulatorsA program which acts like the native console of a video game, allowing it to run on other computers. Allows PCs to run games which may be designed to run on a console.
  40. 40Virtual ServersHave a small number of physical servers with a number of virtual servers on them. They operate as a physical server but multiple virtual servers can be stored on one physical server. Known as virtualisation.
  41. 41Java Interpret Intermediate CodeIt compiles its code into bytecode which can be easily translated by a Java virtual machine. This means that the same bytecode language can be used for different devices. Only the virtual machine needs to be adapted for different devices instead of the language of bytecode.

Informationen

Beschreibung
AS level Computing Karteikarten am SLR 4 - Operating Systems / Systems Software, erstellt von Kyle Clinch am 13/01/2020.
Erstellt von
Kyle Clinch
Aufrufe
1
Bewertung

Feedback

Worum geht es?

Wie gefällt dir das neue Design?

Dein Eindruck