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GCSE Computer Science (OCR) > 2.6 Data Representation COMPLETE > Flashcards

2.6 Data Representation COMPLETE Flashcards

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1
Q

What is the order of data size?

A 
Bit - single digit (0 or 1)
Nibble - 4 bits
Byte - 8 bits
Kilobyte - 1024 bytes
Megabyte - 1024 KB
Gigabyte - 1024 MB
Terabyte - 1024 GB
Petabyte - 1024 TB
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2
Q

How do computers understand binary?

A

They don’t understand the numbers 1 and 0, they understand flashes of electricity that pass through the transistors.
1 = Electricity pulse
0 = No electricity pulse

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3
Q

What number system is binary?

A

Base 2:

2 possibilities - 1 or 0).

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4
Q

Define vector

A

An image drawn by a set of mathematical formulas and can be scaled infinitely without any loss in quality.

Every line and shape has a value that changes when the image expands.

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5
Q

Define bitmap

A

Page is divided into an invisible grid and each pixel is assigned a colour in binary (colour depth).

Higher bit depth = Higher image quality.

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6
Q

What is PPI and DPI?

A

Pixels per inch.

Dots per inch.

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7
Q

What happens if a pixel is to represent more than 1 colour?

A

We need to use more bits to make a range of colours available.

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8
Q

How do you find out how many bits represent colours?

A

2 to the power of the number of bits = number of colours.

1 bit = 2 colours.
2 bits = 4 colours.
3 bits = 8 colours.

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9
Q

What happens with greater colour depth?

A

The more:
Realistic colours there are
Data needs to be stored.
File size on the disk is needed.

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10
Q

What happens with higher resolution?

A

There are more pixels, higher quality and higher image file size.

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11
Q

What is digital sound broken down into?

A

Thousands of samples per second - each of which are stored as binary data.

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12
Q

What does the quality of the samples depend on?

A

1) Sample frequency.
2) Sample size / bit depth.
3) Bit rate.

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13
Q

Define sample rate

A

No. of audio samples captured every second.

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14
Q

Define analogue

A

Made up of a variation of dynamic and frequencies.

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15
Q

Define sampling

A

Recording snippets of sounds at set intervals.

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16
Q

Define character set

A

The possible characters that can be represented in a computer system.

E.g. ASCII and Unicode.

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17
Q

Define metadata

A

Image data that allows the computer to recreate the image from the binary data in the file.

Examples:
Dimensions.
Number of bits per pixel.
Location.
Data and File type.
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18
Q

Define image size

A

Width and height of a bitmapped image, measured in pixels.

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19
Q

If an image has its colour depth increased what is the effect?

A

The file size is bigger.

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20
Q

Define overflow error

A

When the binary number is too big than actually possible

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21
Q

What are the hexadecimal numbers compared to denary numbers?

A 
A = 10
B = 11
C = 12
D = 13
E = 14
F = 15
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22
Q

Define lossy compression

A

The file is compressed and data is lost. It compresses more than lossless

Should be used in audio files.

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23
Q

Define loseless compression

A

The file is compressed; no data has been lost (file size is just smaller, but it isn’t as compressed as lossy ).

Should be used in text documents.

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24
Q

What is the effect of multiplying the binary number by 2?

A

The number is shifted to the left by 1 bit

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25
Q

What is the effect of dividing a binary number by 2?

A

The number is shifted to the right by 1 bit

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26
Q

Define underflow

A

When the binary number is too small than actually possible

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27
Q

All data processed by a computer must be converted into ______ format

A

binary

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28
Q

A computer processor uses billions of ___________ acting as switches, which only act on the binary states on and off

A

transistors

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29
Q

All data and instructions in a computer are represented by…

A

the binary digits 1 (on) and 2 (off)

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30
Q

What binary digit represents ‘on’?

A

1

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31
Q

What binary digit represents ‘off’?

A

0

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32
Q

To be processed, instructions and data are converted to…

A

strings of 1s and 0s

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33
Q

Images and sounds must be _________ to be processed

A

digitised

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34
Q

What do inputs such as the keyboard and mouse send to the processor to be processed?

A

Combinations of 1s and 0s

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35
Q

One unit, either a 1 or a 0, is called a…

A

bit

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36
Q

What is bit short for?

A

Binary digit

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37
Q

True/False: More than one digit is needed to represent an item of data (such as a letter), in binary

A

True

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38
Q

True/False: Bits are organised into groups

A

True

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39
Q

4 bits = 1…

A

nibble

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40
Q

8 bits = 1…

A

byte

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41
Q

True/False: Bytes are grouped into small units

A

False, they are grouped into larger units

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42
Q

How many bytes are in a kilobyte?

A

1000

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43
Q

How many kilobytes are in a megabyte?

A

1000

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44
Q

How many megabytes are in a gigabyte?

A

1000

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45
Q

How many gigabytes are in a terabyte?

A

1000

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46
Q

How many terabytes are in a petabyte?

A

1000

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47
Q

What is the abbreviation for kilobyte?

A

KB

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48
Q

What is the abbreviation for megabyte?

A

MB

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49
Q

What is the abbreviation for gigabyte?

A

GB

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50
Q

What is the abbreviation for terabyte?

A

TB

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51
Q

What is the abbreviation for petabyte?

A

PB

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52
Q

How many bytes are there exactly in a kilobyte?

A

1024

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53
Q

When performing calculations, how many bytes do we say are in a kilobyte?

A

1000

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54
Q

The binary system is a base-_ number system

A

2

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55
Q

Why is the binary system a base-2 number system?

A

It uses two digits, 0 and 1

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56
Q

The denary system is a base-__ number system

A

10

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57
Q

Why is the denary system a base-10 number system?

A

It uses 10 digits, 0 to 9

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58
Q

The hexadecimal system is a base-__ number system

A

16

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59
Q

Why is the hexadecimal number system a base-16 number system?

A

It uses 16 digits, 0 to 15

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60
Q

In any system, the value associated with any digit is given by its…

A

place value

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61
Q

The value of each position in place value increases as the…

A

power of its base

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62
Q

What is the value of the 1st digit in an 8-bit binary number?

A

128

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63
Q

What is the value of the 2nd digit in an 8-bit binary number?

A

64

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64
Q

What is the value of the 3rd digit in an 8-bit binary number?

A

32

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65
Q

What is the value of the 4th digit in an 8-bit binary number?

A

16

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66
Q

What is the value of the 5th digit in an 8-bit binary number?

A

8

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67
Q

What is the value of the 6th digit in an 8-bit binary number?

A

4

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68
Q

What is the value of the 7th digit in an 8-bit binary number?

A

2

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69
Q

What is the value of the 8th digit in an 8-bit binary number?

A

1

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70
Q

What is 10 to the power of 7?

A

10,000,000

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71
Q

What is 10 to the power of 4?

A

10,000

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72
Q

True/False: You can convert denary numbers with values from 0 to 255 into 8 bit binary numbers

A

True

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73
Q

To convert numbers above 255 to binary, more ____ are required than 8 bit binary

A

bits

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74
Q

What are denary numbers also called?

A

Decimal numbers

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75
Q

Convert 234 to binary

A

11101010

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76
Q

Convert 42 to binary

A

00101010

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77
Q

Convert 87 to binary

A

01010111

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78
Q

Convert 67 to binary

A

01000011

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79
Q

Convert 12 to binary

A

00001100

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80
Q

Convert 6 to binary

A

00000110

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81
Q

Convert 124 to binary

A

01111100

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82
Q

Convert 183 to binary

A

10110111

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83
Q

Convert 132 to binary

A

10000100

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84
Q

Convert 245 to binary

A

11110101

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85
Q

How can you check you are correct in a denary to binary conversion?

A

By converting your binary number back into a denary number

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86
Q

True/False: Binary numbers can also be converted to denary numbers

A

True

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87
Q

What is 10001010 in denary?

A

138

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88
Q

What is 01011101 in denary?

A

93

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89
Q

What is 11010110 in denary?

A

214

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90
Q

What is 00011010 in denary?

A

26

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91
Q

What is 10100101 in denary?

A

165

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92
Q

What is 10101010 in denary?

A

170

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93
Q

What is 01010101 in denary?

A

85

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94
Q

What is 10010101 in denary?

A

149

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95
Q

What is 1 + 0 in binary addition?

A

1

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96
Q

What is 0 + 0 in binary addition?

A

0

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97
Q

What is 1 + 1 in binary addition?

A

10, you need to write the 0 and carry the 1 to the left

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98
Q

When do overflow errors occur?

A

When a calculation produces a result that is greater than the computer can deal with

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99
Q

What is the issue with the result of the binary addition 10110101 + 11001111?

A

There will be an overflow error (110000100)

100
Q

What is wrong with the number 110000100?

A

It cannot be represented by an 8 bit number - a 9th bit is required. This is an overflow

101
Q

Why must programmers make allowances for errors such as overflow?

A

To prevent serious errors or disasters

102
Q

Binary shifts are used when…

A

multiplying or dividing binary numbers by powers of 2

103
Q

Binary shifts are the equivalent of… (in terms of denary)

A

multiplying denary numbers by a power of 10 and moving the digits to the left, and writing zeros at the right-hand end

104
Q

When you divide binary numbers by powers of 2, you move bits to the…

A

right

105
Q

What is a right shift?

A

Moving bits of a binary number to the right

106
Q

True/False: Right shifts make binary numbers larger

A

False, they make them smaller

107
Q

True/False: Left shifts divide binary numbers

A

False, they multiply them

108
Q

Hexadecimal is a base-__ number system

A

16

109
Q

Hexadecimal numbers need __ digits

A

16

110
Q

There are no denary digits beyond _

A

9

111
Q

How are denary numbers from 10 to 15 represented in hexadecimal?

A

With the upper case letters A to F

112
Q

How is the denary number 10 represented in hexadecimal?

A

A

113
Q

How is the denary number 11 represented in hexadecimal?

A

B

114
Q

How is the denary number 12 represented in hexadecimal?

A

C

115
Q

How is the denary number 13 represented in hexadecimal?

A

D

116
Q

How is the denary number 14 represented in hexadecimal?

A

E

117
Q

How is the denary number 15 represented in hexadecimal?

A

F

118
Q

What symbol is used to signify that a number is given in hexadecimal notation?

A

#

119
Q

True/False: All denary numbers up to 255 can be represented by hexadecimal numbers with only two digits

A

True

120
Q

All denary numbers up to 255 can be represented by hexadecimal numbers with only _ digits

A

2

121
Q

Hexadecimal numbers are used to help programmers…

A

manipulate large binary numbers

122
Q

True/False: Computers use hexadecimal numbers

A

False, they only understand binary

123
Q

Hexadecimal numbers represent long binary numbers using…

A

fewer digits

124
Q

How do hexadecimal numbers represent long binary numbers using fewer digits?

A

Every 8 digits of a binary number can be represented by two hexadecimal digits

125
Q

When converting binary to hexadecimal, first you must split the 8 byte into…

A

two 4-bit nibbles

126
Q

When converting binary to hexadecimal, once you have split the 8 bit byte into two 4-bit nibbles you…

A

convert the bits in each nibble into denary numbers using the place value

127
Q

When converting binary to hexadecimal, after you have converted each nibble into denary numbers using place value you…

A

add these together to give the hexadecimal

128
Q

True/False: Converting hexadecimal to binary reverses the process of converting binary to a hexadecimal number

A

True

129
Q

When converting hexadecimal to binary, each hecadecimal digit is first converted to…

A

denary

130
Q

After each hexadecimal has been converted to denary, when converting hexadecimal to binary, what is each denary number converted to?

A

A nibble

131
Q

After denary numbers are converted to nibbles, when converting hexadecimal to binary, what happens to the nibbles?

A

They are combined to give the binary number

132
Q

Why is hexadecimal notation used?

A

To help humans cope with long strings of binary digits - they are much shorter in hexadecimal

133
Q

True/False: MAC addresses are given in hexadecimal form

A

True

134
Q

When a computer malfunctions, error code numbers are usually given in ___________ form

A

hexadecimal

135
Q

True/False: Hexadecimal is used to represent numerical values in assembly language

A

True

136
Q

True colour uses __ bits to code every available colour variation

A

24

137
Q

Each colour variation is represented by three 8 bit numbers that can be simplified to…

A

3 2-digit hexadecimal ones

138
Q

It is far easier/harder to remember and enter the six digits of a hexadecimal number than the 24 digits of a binary number

A

easier

139
Q

Check digits are used to…

A

ensure that a sequence of numbers has been entered correctly

140
Q

Transcription errors

A

Errors made when entering data

141
Q

Check digits are used to flag up what type of errors?

A

Transcription errors

142
Q

Give an example of a code that uses check digits

A

Any from product codes/barcodes and ISBNs on books

143
Q

The value of the check digit is usually calculated from…

A

the other data being sent

144
Q

Computers represent text characters, numbers and symbols in binary as…

A

strings of 1s and 0s

145
Q

What does ASCII stand for?

A

American Standard Code for Information Interchange

146
Q

Text and characters are represented by…

A

ASCII code

147
Q

ASCII is a _-bit code

A

7

148
Q

There are ___ code sequences representing english characters and control actions such as space and shift

A

128

149
Q

Give an example of a control action

A

Any from space, shift, etc

150
Q

The _________ ___ is the list of binary codes that can be recognised by the computer hardware and software

A

character set

151
Q

ASCII codes are grouped according to…

A

function

152
Q

What is included in the ASCII code group 0-32?

A

Control codes such as shift and space

153
Q

What is included in the ASCII code group 65-90?

A

Upper case characters such as A, Z

154
Q

Extended ASCII code uses _ bits

A

8

155
Q

The fact that extended ASCII uses 8 bits means there are ___ code sequences

A

256

156
Q

What does extended ASCII include that ASCII doesn’t?

A

Mathematical characters such as pie and symbols for graphics

157
Q

Extended ASCII code has/has not been standardised in the same way as the 7-bit code has

A

has not

158
Q

In terms of extended ASCII code, different manufacturers use different codes for different __________

A

characters

159
Q

Extended ASCII data can/cannot be transferred across platforms accurately

A

cannot

160
Q

There are/are not enough codes to represent different languages in extended ASCII

A

are not

161
Q

Unicode has become the universal ________

A

standard

162
Q

Unicode is used by…

A

the major hardware and software manufacturers

163
Q

Unicode can represent text in…

A

all known human languages

164
Q

Unicode can use up to 32 bits to represent over…

A

1 million characters

165
Q

True/False: The fist 128 characters of Unicode correspond to 7-bit ASCII

A

True

166
Q

In pseudocode, programming languages have functions to return the ASCII code for characters in ______

A

denary

167
Q

In a computer all images are represented as…

A

strings of 1s and 0s

168
Q

pixel

A

Small points of colour that a digital image is composed of

169
Q

What is pixel short for?

A

pixel element

170
Q

Each pixel has its own individual ______

A

colour

171
Q

The greater the number of pixels in a picture, the greater…

A

the detail in the picture

172
Q

The size of an image is given as the number of…

A

pixels in its width and height

173
Q

When a small image is enlarged to cover a large area it is…

A

less sharp

174
Q

Why are small images less sharp when they are enlarged?

A

There are fewer pixels per unit area

175
Q

What will happen to a small image when it is enlarged?

A

It will become blurred

176
Q

If an image has fewer pixels per unit of area, it has a lower __________

A

resolution

177
Q

What does the resolution of an image describe?

A

The number of pixels per unit area

178
Q

Colour depth

A

The number of bits used to encode the colour of each pixel

179
Q

In terms of colour depth - the more bits used to encode the colour, the greater the number of…

A

actual colours that can be represented in the image

180
Q

What does the colour depth mean in terms of the quality of an image?

A

The higher the colour depth, the more detailed an image will be

181
Q

Modern cameras and smartphones produce images with a colour depth of __-bits

A

24

182
Q

The size of an image file in bits depends on… (give 2)

A

Image size and colour depth

183
Q

How do we calculate the file size in bits of an image file?

A

Width x height x colour depth

184
Q

The better the image quality, the ______ the file size

A

larger

185
Q

When can large file sizes be a problem?

A

If they are being transferred electronically or storage space is limited

186
Q

Metadata

A

extra information about the image stored within the file

187
Q

Give 3 things that may be included in metadata

A

Any 3 from make and model number of the camera, dimensions of the image, file size, speed and apeture settings, GPS data showing the location where an image was taken, etc

188
Q

Why should you take care when uploading images to social networking sites if GPS metadata is included in the file?

A

Strangers will be able to see your location

189
Q

Sound can be represented in digital form as streams of…

A

1s and 0s

190
Q

Sound is caused by…

A

vibrations travelling through a medium such as air, water or a metal

191
Q

What do sound recordings convert?

A

Changes in air pressure into voltage changes

192
Q

Sound recordings convert the changes in air pressure into volate changes. These are ________ recordings

A

analogue

193
Q

Samples of the sound wave are taken at…

A

regular fixed intervals

194
Q

Sampling frequency

A

When samples of the sound wave are taken at regular fixed intervals

195
Q

A high sampling frequency gives a…

A

more accurate reproduction of the analogue wave form

196
Q

Transistors are either __ or ___ and cannot continuously reproduce analogue changes

A

on or off

197
Q

Digital recordings use _________ of the sound at regular fixed intervals and then play them back one after the other

A

snapshots

198
Q

Samples

A

Snapshots of a sound at regular fixed intervals

199
Q

A _______ _____ _________ is like an animated film that consists of many still images with tiny differences between them

A

digital sound recording

200
Q

How is a digital sound recording like an animated film that consists of many still images with tiny differences between them?

A

When they are played back quickly it creates the illusion of movement

201
Q

bit depth/sample size

A

Describes the number of bits used to encode each sample

202
Q

A high bit depth allows more/less data to be stored and allows the dynamic range of the sound to be more/less accurately represented

A

more, more

203
Q

True/False: In terms of bit depth, using 8 bits allows 255 graduations of volume

A

False, it allows 256

204
Q

How does the fact that CDs are recorded in stereo and so have two channels impact the file size?

A

It will be doubled

205
Q

Dynamic range

A

The range of volume in sound

206
Q

What does the quality of digital audio depend on?

A

Sampling frequency and bit depth

207
Q

The higher the sample frequency and bit depth, the larger/smaller the size of the audio file

A

larger

208
Q

Bit rate

A

The amount of data processed every second

209
Q

What is the equation for bit rate?

A

bit rate = sample frequency x bit depth

210
Q

What is the equation for file size (bits)?

A

file size (bits) = sampling frequency x bit depth x recording length (seconds) or = bit rate x recording length (seconds)

211
Q

How can the sizes of large files be reduced?

A

Using compression algorithms

212
Q

What do compression algorithms do?

A

Repackage data or remove some of it

213
Q

What does lossless compression do?

A

Reduces file sizes without deleting any data

214
Q

True/False: With lossless compression, nothing is lost

A

True

215
Q

How is data compressed with lossless compression?

A

Looks for redundancy where the same data is stored any times and groups this data into one reference

216
Q

When is lossless compression commonly used?

A

Text files and graphic files with a low colour depth

217
Q

Give an example of a less successful use of lossless compression

A

Audio files, 24-bit colour files

218
Q

Compressed text files use lossless/lossy compression

A

lossless

219
Q

GIF and PNG image files use lossless/lossy compression

A

lossless

220
Q

FLAC and ALAC audio files use lossless/lossy compression

A

lossless

221
Q

Why are FLAC and ALAC audio files becoming more popular on downloading websites for people who prioritise sound quality over small file size?

A

They can reduce the size of an uncompressed file by about 50%

222
Q

What does FLAC stand for?

A

Free Lossless Audio Codec

223
Q

What does ALAC stand for?

A

Apple Lossless Audio Codec

224
Q

What does lossy compression do?

A

Reduces file size by deleting some data

225
Q

When using lossy compression, the original can never/can be reconstituted - it has been irreversibly changed

A

can never

226
Q

How is data compressed in image files with lossy compression?

A

Algorithms analyse the image and find areas where there are only slight differences - these are given the same value and the file can be rewitten using fewer bits

227
Q

In lossy compression with image files, __________ analyse the image and find areas where there are only slight differences

A

algorithms

228
Q

In lossy compression with image files, what happens once an algorithm has analysed the image and found areas where there are only slight differences?

A

These are given the same value and the file can be rewritten using fewer bits

229
Q

How is data compressed in digital sound recordings with lossy compression?

A

Very small variations in frequency, tone and volume are removed to reduce the file size as the human ear cannot detect these small differences

230
Q

In lossy compression with digital sound recordings, very small variations of what are removed?

A

Frequency, tone and volume

231
Q

In lossy compression with digital sound recordings, why are very small variations of frequency, tone and volume removed?

A

To reduce file size as the human ear cannot detect these small differences

232
Q

When is lossy compression commonly used?

A

Image files and digital sound recordings

233
Q

When is lossy compression not used?

A

Text files

234
Q

.mp3 audio files use lossless/lossy compression

A

lossy

235
Q

.jpg image files use lossless/lossy compression

A

lossy

236
Q

True/False: An MP3 file is usually about one tenth of the size of an uncompressed file, so more files can be stored on discs and SD cards

A

True

237
Q

True/False: Billions of video, audio, multimedia and image files are uploaded and downloaded each day

A

True

238
Q

Smaller file sizes make file transfer more _________

A

efficient

239
Q

Smaller file sizes reduce the requirements for…

A

storage space

240
Q

An advantage of compression is that more/less internet bandwidth is used when files are downloaded and uploaded

A

less

241
Q

An advantage of compression is that transfer speed is slower/quicker

A

quicker

242
Q

An advantage of compression is that more/less storage space is needed

A

less

243
Q

An advantage of compression is that smaller/larger files reduce congestion on the internet

A

smaller

244
Q

An advantage of compression is that ____ and _____ files can be streamed

A

audio and video

245
Q

Give 3 advantages of file compression

A

Any 3 from less internet bandwidth is used when files are downloaded/uploaded, transfer speed is quicker, less storage space needed, smaller files reduce congestion and audio and video files can be streamed

GCSE Computer Science (OCR) (15 decks)

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