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GCSE Computer Science > 1.2 Memory and Storage > Flashcards

1.2 Memory and Storage Flashcards

flashcards made by my year 10 self so thanks <3 (60 cards)

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1
Q

What does primary storage consist of?

A

RAM, ROM, registers, and cache

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2
Q

Why is primary storage needed?

A

1) holds the data and instructions which the CPU needs access to while a computer is running
2) the CPU can access data from primary storage much quicker than secondary storage

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3
Q

What is RAM?

A

volatile, read and write, large in comparison to ROM

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4
Q

What does volatile mean?

A

Contents are lost when the power is turned off. Data is temporary and requires power to retain data.

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5
Q

What does RAM hold?

A

Holds the operating system, programs, and data in use by the CPU when the computer is running.

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6
Q

What is ROM?

A

non-volatile (contents remain when power is off), read only, small in comparison to RAM

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7
Q

What does ROM hold?

A

1) Stores the BIOS and instructions needed to boot up the computer.
2) Programs may be stored in ROM in embedded systems.

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8
Q

Why must ROM be non-volatile?

A

ROM must retain its start-up instructions when the power is off so must be non-volatile

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9
Q

Where is virtual memory stored and why is it needed?

A

1) Held on the hard disk
2) Needed when there’s not enough physical RAM to store the open programs

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10
Q

Describe how programs are transferred to and from virtual memory.

A

1) Programs are transferred out to virtual memory from RAM when they are not currently being executed, creating space in RAM for a new program.
2) Programs are transferred back to RAM from virtual memory when they are needed.

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11
Q

What is secondary storage and why is it needed?

A

1) Long term, non-volatile storage of files and programs
2) Needed because ROM is read only and RAM is volatile

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12
Q

What is secondary storage used for?

A

Storage of programs and data when the power is off, semi-permanent storage of data that can change, back up and archive of data files

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13
Q

Examples of optical storage

A

CD, DVD, Blu-ray

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14
Q

Characteristics of optical storage

A

1) Low capacity
2) Slow to access data
3) Thin, lightweight and portable
4) Prone to scratches

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15
Q

Examples of magnetic storage

A

HDD (hard disk drive), floppy disk

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16
Q

Characteristics of magnetic storage

A

1) high storage capacity
2) quick to access data
3) has moving parts which eventually fail
4) hard disks work better if defragmented

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17
Q

Examples of solid state storage

A

SSD (solid state drive), USB stick, memory card

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18
Q

Characteristics of solid state storage

A

1) medium storage capacity
2) very quick to access data
3) no moving parts, very reliable
4) no need to defragment
5) limited no. read/write cycles
6) expensive, low power, no noise

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19
Q

Suitability: reliability

A

worst-solid state, best-magnetic

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20
Q

Suitability: capacity

A

worst-optical, best-magnetic

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21
Q

Suitability: cost per MB

A

worst-solid state, best-magnetic

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22
Q

Suitability: durability

A

worst-magnetic, best-solid state

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23
Q

Suitability: portability

A

worst-magnetic, best-solid state

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24
Q

Suitability: read/write speed

A

worst-optical, best-solid state

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25
suitability example optical
videogames
26
suitability example solid state
helmet cam
27
suitability example magnetic (can also use cloud based storage)
computer, travel agent backup
28
Why is data stored in binary?
With just two states, electronic components are easier to manufacture, therefore cheaper and more reliable
29
Examples of binary data
RAM, optical disk, hard disk, flash memory
30
What does a binary right shift do?
divides number by two
31
What does a binary left shift do?
multiplies number by two
32
What is an overflow error?
An error that occurs when the result of an addition cannot fit all the bits available, usually caused by a carry
33
Why is hexadecimal used?
It is easier for humans to read and use than binary and less prone to mistakes
34
Text file size calculation
bits per character x number of characters
35
Image file size calculation
colour depth x image height (px) x image width (px)
36
Sound file size calculation
Sample rate x duration (s) x bit depth
37
What is a character set?
A defined list of characters (each with a unique binary code) recognised by the computer which allows devices to communicate.
38
What is ASCII?
A 7 bit character set which holds 128 English characters, letters, numbers
39
What is Extended ASCII?
An 8 bit character set which holds 256 characters
40
What is Unicode?
A 24 bit character set which can express all world languages and emojis. ASII doesn't have enough data for other languages
41
How can images be stored?
In binary as bitmaps or vectors
42
What is metadata?
Additional data stored with the image to define the width, height, colour depth and colour palette
43
The greater the colour depth and resolution...
...the larger the file size of the image
44
Representing images: num of bits
1) num of bits per pixel depends on num of colours required (1 bit = 2 colours) 2) the num of colours = 2^n (n = num of bits per pixel)
45
What is the colour depth?
The number of bits per pixel
46
Representing sound:
1) sample rate (Hz) x bit depth x duration in seconds 2) bit depth = number of bits per sample, the higher the no. of bits, the greater the quality of sound and larger the file size 3) sample rate = number of samples stored per second (Hz), the higher the no. of samples, the higher the quality of sound and the larger the file size
47
How are images stored as bitmaps?
Images are stored as bitmaps with which are made up of thousands of tiny squares called pixels. each pixel is represented by a binary number. (Each pixel has a specific colour, represented by a specific code)
48
What is resolution?
The density of a pixel in an image. Pixels per inch. Higher resolution means greater quality but greater file size
49
How is analogue sound stored digitally?
The analogue sound is sampled at regular intervals. This means the height of a sound wave (amplitude) is measured. Analogue sounds must be stored in binary
50
Factors that affect the size and quality of a sound file
1) Sample interval - gap between each sample 2) Sample frequency - how many samples are taken a second 3) Sample size - the number of bits given to each sample 4) Bit rate - the number of bits used per second
51
What does increasing the frequency mean?
Increasing the frequency means the recording sounds closer to the original. Increasing the sample size means the recording is higher quality (more detail, such as quieter sounds)
52
Why is compression needed?
To reduce the size of a file. This means we can store more files and it's faster to download/upload/transfer files
53
Compression:
1) reducing the number of bits in a file 2) making the storage capacity of the file lower 3) making data transfer of files quicker 4) useful because data can be stored on a data device and transferred quicker
54
Lossy compression
Permanently deletes data, cannot be retrieved, most effective but quality is reduced
55
What is lossy compression suitable for?
images/sound/video
56
Lossless compression
temporarily reduces size of a file, file can be restored to original size and quality, not as effective as lossy
57
What is lossless compression suitable for?
Word documents and executable files
58
def sample rate
measured in hertz
59
def duration
the number of seconds of audio the sound file contains
60
def bit depth
the number of bits available to store each sample

GCSE Computer Science (13 decks)

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