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Computer Science > Data Storage > Flashcards

Data Storage Flashcards

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1
Q

What are the units in Computer Science

A

Bit
Nibble
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte
Petabyte
Hertz

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2
Q

How many bits in a byte

A

8

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3
Q

How many bits or bytes in a nibble

A

Half a byte
4 bits

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4
Q

How many bytes in a kilobyte

A

1000

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5
Q

How many kilobytes in a megabyte

A

1000 kilobytes
or 1 million bytes

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6
Q

How many megabytes in a gigabyte

A

1000 megabytes

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7
Q

How many gigabytes in a terabyte

A

1000 gigabytes

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8
Q

How many terabytes in a petabyte

A

1000 terabytes

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9
Q

What are the two only states that a computer can understand

A

Power on
Power off

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10
Q

What is the power term called

A

Switches

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11
Q

What are switches represented by

A

Power on represents a 1
Power off represents a 0

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12
Q

What is the table layout for binary and denary

A

128, 64, 32, 16, 8, 4, 2 1

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13
Q

What is denary

A

A whole number

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14
Q

What is binary

A

An 8 bit number

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15
Q

What is 32 in binary. Show steps

A

128, 64, 32, 16, 8, 4, 2 1
0 0 1 0 0 0 0 0

00100000

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16
Q

What is 78 in binary

A

128 64 32 16 8 4 2 1
0 1 0 0 1 1 1 0
01001110

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17
Q

How do we convert binary to denary

A

128, 64, 32, 16, 8, 4, 2 1

If there is a 0 under a number, we don’t add that number up. If there is a 1 under the number, we add that number. For example If we have the binary number of
10001001
Substitute this in the table.
There is a 1 underneath 128, 8 and 1, so add all those numbers up, which makes 137. For this example we say that 10001001 is 137 in denary

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18
Q

Convert 00100111 into binary

A

39

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19
Q

Whats the highest possible denary number and binary number

A

11111111
255

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20
Q

What is hexadecimal

A

A number that uses a base of 16. It starts from 0 to 9, then from A to F

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21
Q

How do we convert hexadecimal to denary

A

Multiply the left hand digit by 16, then add the units

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22
Q

How do we convert hex 7 to denary

A

Multiply 7 and 16.
Then add 10
Hex 7 is 122 in denary form and 7 in decimal form

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23
Q

What is hex 27 in denary

A

(2x16) + 7 = 39 in denary form

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24
Q

How do we convert denary to hexadecimal

A

Divide the denary number by 16. The remainder gives the units.

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25
Q

What is denary 72 in hexadecimal

A

72/16 = 4.5: 4 remainder 5
45 in hexadecimal

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26
Q

How do we convert binary to hexadecimal

A
  1. Take a binary word of 8 bits
    11100101
  2. Divide into two nibbles of 4 bits
    1110 and 0101
  3. Convert each nibble into its hexadecimal value

1110 = 14 = E in Hex
0101 = 5 in Hex

11100101 = E5 in Hex

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27
Q

How do we convert hexadecimal to binary. What is 3B in binary

A

Split the two hex characters
3 = 0011 and B = 1011
3B = 00111011

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28
Q

What is A5 in binary

A

A = 10 = 1010
5 = 0101

A5 in hex = 10100101

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29
Q

What is hex 21 in binary

A

2 = 0010 and 1 = 0001

21 in hex = 00100001

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30
Q

Why do we use hex

A
  1. It is easier to convert between hex and binary
  2. People are likely to make less digit errors
  3. Quicker to write and type since hex digit only takes up 1 digit rather than 4 bits
  4. Much simpler to remember a hex value than a binary value
  5. An advantage for programmers and Computer Scientists
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31
Q

How does numbers work on computers

A

Computers work with a fixed number of bits at a time.

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32
Q

What is an overflow error

A

When the result of the addition is too large for the number of bits that a computer works with

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33
Q

What are the two logical binary shift operations

A

Left shift
Right shift

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34
Q

What is a binary shift left

A

A binary shift left of one bit moves all the bits one place to the left. The vacant bit spaces are replaced with 0

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35
Q

How does a binary shift left have an affect on the number

A

The number is doubled

Eg: 1000 = 8
Shift left once = 10000 = 16

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36
Q

What is a binary shift right and what is the effect

A

A binary shift right of two places halves the number and rounds down each time

Eg:
1000 = 8
Shift right once = 100 = 4
Shift right twice = 10 = 2

Eg: 2

1001 = 9
Shift right once = 100 = 4
Shift right twice = 10 = 2

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37
Q

What are the effects of shifts

A

They can quickly multiply or divide the binary number by 2

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38
Q

How are characters represented in binary

A

Every character on the keyboard is represented by a binary number.

Uppercase letters (capitals) have different values from lowercase letters

Punctuation symbols have their own character code

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39
Q

What are the four mandatory components that a computer needs to contain

A

26 lowercase letters
26 uppercase letters
10 numbers
36 other characters

This creates 98 total characters

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40
Q

What is a character set

A

Collection of characters that a computer recognises from a binary representation

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41
Q

What are character sets a set of

A

Letters
Symbols
Digits

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42
Q

What are three major character sets used today

A

ASCII
Extended ASCII
Unicode

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43
Q

What is ASCII

A

A 7 bit character code, that has 128 different characters that can be encoded.

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44
Q

What is ASCII Extended

A

An 8 bit character code, that has 256 different characters that can be encoded.

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45
Q

How are ASCII character codes setup

A

ASCII codes are normally grouped and ran in sequences.

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46
Q

What are some types of character codes

A

7 bit character code
8 bit character code
16 bit character code

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47
Q

How many different characters can be encoded via a 16 bit character code

A

65536

48
Q

What is Unicode

A

A new code allowing for many more different characters to be used. It has a 16 bit and a 32 bit character code. The 32 bit version gives over 4 billion possible combinations

49
Q

What can we use Unicode for

A

Emoji storing
Writing text

50
Q

How many bytes in a Unicode

A

16 bits = 2 bytes
32 bits = 4 bytes

51
Q

What is an image

A

A visual representation of something, which can consist of a drawing, painting or picture

52
Q

How are digital images stored on a computer

A

BMP
JPG
GIF
PNG
TIFF
SVG
AI
PS

53
Q

What is a bitmap image

A

Images made up of picture elements or pixels

54
Q

What is a pixel

A

The smallest identifiable area of an image

55
Q

How does a pixel plays its part

A

Each pixel is a single colour and assigned a binary value that represents that colour

56
Q

Can we change the pixel colour?

A

Yes. But we have to change the value because the binary value is tied to the original colour

57
Q

What is image resolution

A

The concentration of pixels within a specific area. The area is defined by the image width and height in pixels

58
Q

How do we create an image

A
  1. Each pixel gets a binary value
  2. Each value represents a different colour
  3. Using 1 bit per 1 pixel allows only 2 values: 0 and 1

1 = Black
0 = White

This would create a black and white image

59
Q

What is image resolution measured in

A

DPI (Dots per inch)
PPI (Pixels per inch)

60
Q

How do we increase the number of colours in an image

A

More bits per pixel = More colour combinations

61
Q

How many colours in 1 bit

A

2

62
Q

How many colours in 2 bits

A

4

63
Q

How many colours in 3 bits

A

8

64
Q

How many colours in 4 bits

A

16

65
Q

How many colours is a pixel able to represent

A

A Finite amount of colours

66
Q

What is bit depth

A

Number of bits in each sample

67
Q

What does a higher bit depth give to an image

A

Greater colour range
Better image quality

68
Q

What happens when we reduce colour

A

Size reduction
Fewer bits needed per colour
Fewer bits per pixel

69
Q

What is the effect of modifying the colour depth

A

The number of colours displayed

70
Q

What is a monochrome image

A

An image represented in binary as a bit pattern

71
Q

How are colour values of individual pixels expressed

A

Denary RGB values
Hexadecimal form

72
Q

Why isn’t binary sued for monochrome images

A

Less easier to
Read
Write
Remember
Reduce copied errors
Not used by designers

73
Q

What is the pixel proportion for a monochrome image

A

A proportion of
Red
Blue
Green

From a distance, it makes up a colour

74
Q

What is image metadata

A

Data about data. It is information other than image data which is stored within a file

75
Q

What does metadata include

A

Colour
Resolution
Date created
Author

76
Q

What links file size and resolution

A

The greater the resolution of the image, the greater the file size

77
Q

What is sound

A

Continuous and regular vibrations which result in noise

78
Q

What are the two types of sound signals

A

Digital sound signals
Analogue sound signals

79
Q

What’s the difference between the signals

A

Digital sound is discrete
Analogue sound is continuous

80
Q

How is sound digitized

A

Repeatedly measuring and recording the sound wave

81
Q

How do we store sound on a computer

A

Convert sound to digital form

82
Q

What are two types of Analogue to Digital convertors

A

ADC (Analogue to Digital Convertor) converts input to digital signals

DAC (Digital to Audio Convertor) converts digital signals to output

83
Q

What is a sound sample

A

A measure of amplitude of a sound wave at a given time

84
Q

What are the units of a sound sample

A

Bit depth
Sample rate

85
Q

What is the bit depth

A

The factor that determines how closely the wave is sampled at the y axis

86
Q

What is the sample rate

A

Number of samples taken per second

87
Q

What is the measurement of sample rate

A

Hertz (Hz)
1Hz = 1 sample per second

88
Q

What is sample resolution

A

The number of bits (audio bit depth) used to record each measurement

89
Q

What is the effect of increasing the number of bits per sample

A

Enables the height of the wave to be more accurately measured, but an increased file size

90
Q

What is another word for sample rate per second

A

Frequency

91
Q

What is the effect of frequency

A

Has an effect of the level of detail in the digital representation

92
Q

What is the effect of increasing frequency

A

The greater the frequency, the greater the accuracy and larger the file size

93
Q

What is file size measured in

A

Bits

94
Q

How many bytes in a bit

A

1 bit = 0.125 bytes

95
Q

What is the equation for sound file size

A

Sample rate x Bit depth x duration

96
Q

How do we get improved recorded sound quality

A

Large frequency of sound sampling
Great accuracy of recorded wave height

97
Q

What is the effect of increasing the sample rate

A

More data points recorded

98
Q

Approximately, what can we hear sounds from

A

20 - 20000 Hz
Younger people can hear sounds at higher frequencies

99
Q

What is another word for height

A

Amplitude

100
Q

How do we convert music into a file

A
  1. The wave amplitude is measured at regular intervals
  2. These are then turned into binary
101
Q

What is the effect of a smaller interval

A

Larger files
Closer sound to original
Better sound quality

102
Q

What is compression

A

Reduces the file size of an image or object

103
Q

What is decompression

A

The process of expanding computer data to its normal size so that it can be read by a computer.

104
Q

What is compression used for

A

Sound
Images
Video files

105
Q

What happens if we use different compression levels

A

Different compression levels affect quality of compressed images.

Data elimination
Size reduction

106
Q

Why should we use smaller file sizes

A

It can improve a site’s performance and loading times. The smaller the file size, the faster the performance

107
Q

What are the two types of compression

A

Lossy
Lossless

108
Q

What is lossy compression

A

Lossy compression reduces the file size, but deletes as much data as possible, permanently. But it is barely noticeable

109
Q

What are the common file standards for lossy compression

A

JPEG: Photo use
MP4: Video file format
MP3: Music format

110
Q

What are the advantages of lossy compression

A
  1. Doesn’t take up as much file space when compressed
  2. Greatly reduces file size
  3. They take up less bandwidth so can be downloaded and streamed more quickly
  4. Lots of software can read lossy files clearly
  5. It is barely noticeable when there is a reduction in size quality
111
Q

What are the disadvantages of lossy compression

A
  1. Data is deleted permanently
  2. Decompression is not applicable for lossy compression
  3. Text or software files will not work as all the data is going to be deleted as files must retain all information of the original
  4. Causes degradation which reduces the image quality
  5. Digital artefacts can appear in images and videos
  6. Noise is seen when there’s contrasting colours
    Removal of sound so
  7. We can’t easily hear the least affect of perceived playback quality
112
Q

What is lossless compression

A

Lossless compression reduces the file size but doesn’t delete any of the original data. It stops metadata and such.

113
Q

What does lossless compression allow us to do

A

It allows you to restore compressed files to its original form.

114
Q

What are common file standards for lossless compression

A

PNG: Is used for images and photos which can include transparency

ZIP: Document compression

GIF: Simple images, animations may be included

FLAC/ALAC: Lossless music format (Free Apple)

115
Q

What are the advantages of lossless compression

A
  1. Can be decompressed, restored to original
  2. No reduction of quality
  3. Can be used on text and software files
  4. No data is deleted
116
Q

What are the disadvantages of lossless compression

A
  1. Takes up a lot more space than lossy compression
  2. Only a small reduction in file size

Computer Science (6 decks)

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