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Computer Science > Memory and Storage 1.2 > Flashcards

Memory and Storage 1.2 Flashcards

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1
Q

what are the uses of primary storage

A

RAM, ROM, registers and cache

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2
Q

why is primary storage needed

A

-access times are faster than secondary storage
-the time taken to complete operations such as the FED cycle is reduced

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3
Q

what are uses of secondary storage

A

operating system, programs and data are held here when not used

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4
Q

why is secondary storage needed

A

-for long term storage of programs and data that are currently not in use

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5
Q

what are uses of tertiary storage

A

storage used for backing up and archiving large amounts of data

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6
Q

what are features of primary storages

A

-they are volatile except ROM
-relatively small capacity compared to secondary hard drive
-loses memory when computer is turned off
-measured in GB
-very fast access compared to secondary storage

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7
Q

What is RAM

A

-temporary storage of instructions and data
-holds information being executed by the processor
-volatile
-holds operating system when the computer is running

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8
Q

what are features of secondary storages

A

-all non-volatile, when we turn power off, they still hold data stored on them
-much large storage capacity compared to primary storage
-measured in TB
-very slow access times compared to primary storage

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9
Q

what is ROM

A

-small piece of read only memory located on the motherboard (soldered)
-non-volatile
-contains very first instructions for the computer to properly boot up(bootstrap)
-software on ROM is called firmware
-is possible to update the BIOS on a ROM chip

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10
Q

function of the BIOS

A

-when the computer is powered on, the CPU reads instructions from ROM to perform self-checks and set up the computer
-(testing if memory is working, see what hardware is present and copy OS into RAM)
-Loads the operating system into RAM
-checks for hardware connected to the computer
-provides basic UI where some settings can be accessed (changing which storage device to lead the OS from)

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11
Q

what is virtual memory

A

-computers have limited amount of RAM
-when RAM is full/not enough physical RAM to store the open programs,
-programs that have not been used recently or not being currently executed to a location on the secondary storage known as virtual memory
-this frees up space in RAM
-programs are transferred back to RAM from virtual memory when they are needed
-allows the computer to remain operational

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12
Q

what is a drive

A

the device that reads and write data from secondary storage

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13
Q

what is media

A

what the data is actually stored on

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14
Q

advantages of magnetic storage

A

-Capacity - High storage
-Cost - low per gigabyte
-Speed - moderate red/write access

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15
Q

disadvantages of magnetic storage

A

-Durability - Moving parts can get damaged if dropped
-Portability - Heavy and bulky making them less convenient for transport
-Reliability - Prone to mechanical failure
-Noise - loud

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16
Q

advantages of optical storage

A

Cost - very low per gigabyte
Durability - No moving parts
Portability - small and no moving parts
Noise - silent

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17
Q

disadvantages of Optical Storage

A

Capacity - very low
Speed - very slow read/write speed
Reliability - Prone to scratches

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18
Q

advantages of solid state storage

A

-capacity - medium storage
-speed - very fast read/write access
-durability - no moving parts
-portability - small and no moving parts
-noise - silent

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19
Q

disadvantages of solid state storage

A

cost - very high per gigabyte
reliability - limited read/write cycles

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20
Q

what are factors for which storage device someone would use

A

-capacity
-speed
portability
-durability
-reliability
-cost

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21
Q

why do computers process data in binary

A

-computers consist of switches
-1 is represented as the switch being open, 0 represents switch being closed

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22
Q

why must happen to data before computers can understand and process it

A

-must be converted to binary

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23
Q

advantages of converting data to binary

A

allows computers to process it at high speeds, perform calculations and store data efficiently

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24
Q

what are character sets

A

-a character set is a defined list of characters recognised by the computers from their binary representation
-each character is represented by a unique binary number

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25
Q

what are examples of well known character sets

A

-ASCII- a 7 bit character set with 2⁷ characters which = 128
(American standard code for information interchange)
-Extended ASCII - an 8 bit character set with 2⁸ characters
-UNICODE - a 24 bit character set with 2²⁴ character( more than 16 million)

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26
Q

how can images be represented

A

images can be stored in binary as bitmaps or vectors

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27
Q

what are bitmap pictures

A

they are constructed from coloured squares called pixels

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28
Q

what are vector pictures

A

they store the mathematics to draw coloured shapes

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29
Q

how are pixel stored

A

in binary, with RGB values (red green blue)

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30
Q

how do the number of bits per pixel vary

A

depends on the number of colours required. Number of colours calculated as 2 to the n, where n in the number of bits for each pixel

31
Q

Colour depth

A

The number of bits stored per pixel in a bitmap image

32
Q

what is metadata

A

-it is the information stored in an image file which helps the computer recreate the image on screen from the binary data in each pixel
-additional data stored with the image to define the width, height, colour depth and colour palette
-without metadata devices would not be able to display the image on screen as intended

33
Q

how does the file size of the image change?

A

the greater the colour depth and resolution, the larger the file size

34
Q

what is resolution

A

the number of pixels

35
Q

what is sound file size and how do you calculate it

A

-it is the total number of bits in a sound.
-(number of samples per second) x (number of bits per sample) x (length of samples in seconds)

36
Q

what is bit depth

A

-the number of bits stored per sample
-the higher the number of bits, the greater the quality of sound, and the larger the file size

37
Q

what is sample rate

A

-the number of samples stored per second
-the higher the number of samples per second, the higher the quality of the sound, and the large the file size

38
Q

what is compression

A

-reducing the number of bits in a file
-making the storage capacity of the file lower
-making data transfer of the file quicker
-useful because more data can be stored on a storage device, and transferred in a smaller amount of time

39
Q

how is sound sampled

A

-sound is recorded by a microphone as an analogue signal (pieces of continually changing data)
-analogue signals are converted into digital data (so computers can read and store sound files) using analogue to digital converters
-to play the sound, digital data is converted into analogue using digital to analogue converter, and is amplified over speakers or headphones

40
Q

effect of increasing bit depth

A

-sound sampled will be closer to the quality of the original recording
-quieter sounded will also be picked up even if they happen at the same time as louder ones
-larger file size

41
Q

effect of increasing the sample rate

A

-analogue recording is sampled more often
-better quality sound and more closely match the original recording
-larger file size

42
Q

what is lossy compression

A

-some of the data is lost and cannot be recovered
-greatly reduces the file size
-reduces the quality of the image/sound
-suitable for images, sound and video
-cannot be used on text and executable files

43
Q

lossless compression

A

-none of the data is lost, it is encoded differently
-can be turned back into original format
-can be used on all types of data
-is usually less effective than lossy compression
-most suitable for documents and executable files

44
Q

benefits of lossy compression

A

-less storage on a device as files are smaller
-streaming and downloading files from the internet is quicker as less bandwidth is used
-allows web pages to load more quickly in web browsers
-commonly used- lots of software can read lossy files

45
Q

cons of lossy

A

-loses data and file cannot be turned back into the original
-cannot be used on text of software files and they need to retain all the information of the original
-worse quality than original(normally unnoticeable)

46
Q

benefits of lossless

A

-data is only removed temporarily so no reduction in quality
-lossless files can be decompressed (turned back into the original)
-can be used on text and software files

47
Q

cons of lossless

A

only a slight reduction in file size, so a large bit of space on your device is used

48
Q

examples of lossy files

A

-MP3 (audio)
-AAC (audio)
-JPEG (image)

49
Q

examples of lossless files

A

-FLAC (audio)
-Zip (files and folders)
-PNG (image)

50
Q

what is volatile memory

A

-it is temporary memory. It requires power to retain its data

51
Q

what is non-volatile memory

A

-it is permanent memory - it keeps its contents even when it has no power

52
Q

what happens to OS when the computer boots up

A

it is copied from the secondary storage to the RAM

53
Q

what happens to applications, files and documents when they are opened

A

they are copied from the secondary storage to RAM. They stay in RAM until the files or applications are closed

54
Q

advantages of using HDD to SDD

A

-cheaper
-higher capacity
-longer read/write life

55
Q

advantages of using SDD to HDD

A

-faster data transfer speeds
-no defragmenting
-more shock-proof
-silent

56
Q

advantages of Optical

A

-very cheaper per GB
-portable
-not damaged by water or shocks

57
Q

why has use for optical discs declined

A

-faster internet speeds, streaming and download services have removed the need for optical discs
-very slow read and write speeds, poor reliability and low capacity

58
Q

what is a left shift

A

-every number is shifted to the left
-for every place shifted left, the number is doubled

59
Q

what is a right shift

A

-every number is shifted to the right
-for every place shifted right, the number is halved

60
Q

what is a overflow

A

-when extra bits are needed after performing a left shift
-computers usually deal with these extra bits by storing them elsewhere

61
Q

what happens when you perform a right shift

A

-bits ‘drop off’ can happen at the end

62
Q

what can left and right shifts cause if they over flow and drop off

A

-lead to a loss of accuracy/data
-can cause software to crash if it does not have a way of dealing with the extra bit when an overflow happens

63
Q

what happens when you press a key

A

-a binary signal is sent to the computer telling it which key you pressed.
-the computer then uses the character set to translate the binary code into a particular character

64
Q

how many bits is in ASCII and how many different characters are tehre

A

-7 bits
-128 characters

65
Q

how man bits per character in unicode and how many different characters are there

A

-16 bits
-149,186 characters

66
Q

how many bits in extended ASCII

A

-8 bits
-256 characters

67
Q

why is UNICODE helpful

A

-covers all major languages, unlike ASCII

68
Q

formula for file size(text)

A

-number of bits per character x number of characters = file size in bits

69
Q

formula for file size(image)

A

image resolution x colour depth = width x height x colour depth = file size in bits

70
Q

disadvantages of virtual memory

A

-can make a computer sow to respond when switching between applications as data transfer speeds from secondary storage are much slower than from RAM

71
Q

why is secondary storage needed

A

-secondary storage is needed to store data long term
-it is non-volatile, which means it will retain data when power is off
-computers could not function without permanent data storage, as all software and data would be lost when switched off
-secondary storage has a high capacity so you can store more data

72
Q

nibble

A

4 bits/half a byte

73
Q

Formula to find the size of an image file

A

(Resolution of height x width) x (colour depth in bytes) = file size in bytes

74
Q

Denary

A

-A number system that is made up of 10 digits(0-9)
-referred to as base-10

Computer Science (12 decks)

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