Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OCR A Level Computer Science > 1.2.1 Systems Software > Flashcards

1.2.1 Systems Software Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What is the OS?

A
  • A piece of software that controls the software and hardware of the computer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is the OS needed?

A
  • Provides the interface between the user and the hardware
  • Provides a platform in which users can run programs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Features of the OS: Multitasking

A
  • When you more than one program opened and running at the same time
  • Processor allocates a small amount of time to each process and cycles between them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Features of the OS: File management

A
  • Data is stored in data and the extension of the filename tells the OS which application to load the file into
  • Allows user to rename, delete, copy and move files
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Features of the OS: User management

A
  • Allows users to log onto the same computer
  • OS retains settings for each user as each user may have different access rights to files and programs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Features of the OS: User interface

A
  • WIMP
  • Visual
  • Intuitive
  • Optimised for touch and mouse gesture input
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is paging?

A
  • Where memory is split into equal sized sections (pages)
  • Physical divisions in which programs are split up to fit in a given number of pages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is an advantage of paging?

A
  • Allows memory to be allocated in a non-contiguous manner - pages of the same process don’t need to be stored together but can be allocated whenever there’s free space in memory
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a disadvantage of paging?

A
  • Inefficient: could separate instructions inside a looping condition and are in different pages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is segmentation?

A
  • Memory is spit into logical sized divisions known as segments, which are complete sections of programs and vary in size
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the advantages of segmentation?

A
  • Segments do not need to be stored continuously across a fixed address space
  • can be moved in and out of memory as required
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the similarities between paging and segmentation?

A
  • Both allow programs to run despite insufficient memory
  • Stored on disk
  • Both pages and segments are transferred into RAM when needed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the differences between paging and segmentation?

A
  • Pages are fixed size, Segments vary in size
  • Pages are made to fit sections of memory, segments are complete sections of programs
  • Pages are physical divisions, segments are logical divisions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is virtual memory?

A
  • An allocated area of a hardware/secondary storage device which is used when there’s not enough physical RAM to store open programs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is an advantage of virtual memory?

A
  • Extends memory available: swapping instructions and data out of RAM into secondary storage means a vast quantity of memory is potentially available
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the disadvantages of virtual memory?

A
  • Accessing a secondary storage medium is slower than accessing RAM, may slow down performance
  • Disk thrashing: When the computer ‘freezes’ due to pages/segments being swapped out too frequently between the hard disk and RAM
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is an interrupt?

A
  • A way of signaling the processor when other devices and applications require attention
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the Interrupt Service Routine (ISR)?

A

Program with a set of instructions that need to be fetched, decoded and executed in order to carry out the operations of the interrupt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Where can ISRs be found?

A

Built into the OS or provided via device drivers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why may the processor be interrupted?

A
  • Hardware device has signaled it has data to be processed
  • Hardware failure has occurred and needs to be addressed
  • Software process needs a service to be provided/ OS function needs to be performed
21
Q

Are ISR priorities important?

A

Yes, interrupts always have a higher priority than normal programs

22
Q

Examples of interrupts for hardware

A
  • Power supply failure
  • Power/reset button pressed
23
Q

Examples of interrupts for the user

A
  • Keyboard presses
  • Tapping an icon to load a new program
24
Q

Examples of interrupts for software

A
  • Arithmetic overflow
  • New log on request
25
Q

Examples of interrupts for I/O devices

A
  • Printer ink supply notification
  • Buffer nearly empty
26
Q

What is scheduling?

A
  • Part of the OS that is responsible for managing the order of processes and how they will be managed to achieve multitasking
26
Q

What does a scheduler manage?

A
  • Which process to execute next
  • The length of time the next process can execute for
27
Q

How does the First Come, First Served scheduling algorithm work?

A
  • Like a supermarket queue / first job is the first to enter the running state
  • Processes are executed in the order they arrive
  • If a process takes a long time, the others behind have to wait
  • Not pre-emptive
28
Q

How does the Shortest Job First scheduling algorithm work?

A
  • Picks the process that takes the shortest amount of time and runs them until they finish
  • Scheduler needs to know how long each process will take
  • Not pre-emptive
29
Q

How does the Round Robin scheduling algorithm work?

A
  • Each process is allocated a fixed amount of time (quantum)
  • If the process is not complete by the end of its time slice, it returns to the back of the ready queue
  • Pre-emptive
30
Q

How does the Shortest Remaining Time scheduling algorithm work?

A
  • Ready queue is sorted by the estimated time to complete the process
  • Processes that arrive with a shorter time to complete the current running process are moved to the running state
  • Pre-emptive
31
Q

How does the Multi-Level Feedback Queues scheduling algorithm work?

A
  • Several ready queues are used, each with a different scheduling algorithm
  • Jobs are able to move between queues as their priorities change
  • Pre-emptive
32
Q

What are the different types of operating systems?

A
  • Distributed OS
  • Embedded OS
  • Multitasking OS
  • Multiuser OS
  • Real Time OS
33
Q

What is the purpose of the distributed OS?

A
  • You can combine the processing power of multiple computers across a network for a single task
  • In distributed computing, the OS controls and co-ordinates the computers, presenting them to the user as if they were a single system
34
Q

What is the purpose of the embedded OS?

A
  • Specialised OS with limited resources and functionality, built in to control a single machine
  • Tend to run on dedicated hardware so they run with maximum efficiency, using low-powered processors
35
Q

What is the purpose of the multitasking OS?

A
  • Each active program is scheduled to receive a tiny time slice in quick rotation, giving the impression they are operating at the same time
36
Q

What is the purpose of the multiuser OS?

A
  • Provides the facilities for multiple users to access the same system
  • Controls the consumption of resources so users can access the system at the same time, without affecting other users
37
Q

What is the BIOS (Basic Input Output System?

A
  • Responsible for loading the OS when the computer first turns on
  • Checks all hardware it needs is connected and working using a Power On Self Test
38
Q

What is the purpose of the boot loader program (bootstrap)?

A
  • Used to load the OS kernel into memory
39
Q

What would happen without the BIOS?

A
  • Nothing could be loaded as RAM doesn’t contain any instructions that could start the boot program
40
Q

Where are the BIOS settings stored?

A
  • In flash memory so they can be changed and are retained when power is turned off
41
Q

What is a device driver?

A
  • Software that tells the OS how to communicate with a device
  • Translates the OS instructions into a series of instructions that a specific piece of hardware will understand
42
Q

What is a virtual machine?

A
  • Program that has the same functionality as a physical computer
43
Q

What is an emulator?

A

A hardware or software that enables one computer system (host) to behave like another computer system (guest)

44
Q

What is intermediate code?

A

Code partly translated between high level and machine language produced by a compiler

45
Q

States some uses of virtual machines

A
  • Creating a test system
  • Running software compatible with different versions and types of OS
  • Running multiple servers
46
Q

How is intermediate code executed?

A
  • At run time, the og program is translated to IC which is passed to the VM
  • Using the VM as an intermediary between the system and source code allows the same code to be used on any program that can run the VM
47
Q

What is the purpose of the real time OS?

A
  • An OS where data is processed as it comes, with responses generated with a guaranteed timeframe
  • Used in safety critical environments, e.g. autopilot, hospitals

OCR A Level Computer Science (36 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions