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Computer Science IGCSE > Topic 1. Data Representation > Flashcards

Topic 1. Data Representation Flashcards

Flashcards on Binary, Text, Sound and Images

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1
Q

What are the advantages of hexadecimal?

A

Easier for humans to read and remember than binary

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2
Q

What is hexadecimal used for?

A

Colour values in photo editing software and Web design
MAC Addresses

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3
Q

What are the rules in binary addition

A

0 + 0 = 0
1 + 0 or 0 + 1 = 1
1 + 1 = 0 carry a 1
1 + 1 + 1 = 1 carry a 1

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4
Q

When does an overflow occur?

A

When the result of adding two binary numbers is greater than the numbers of bits allowed

For example if you added 193+139 on a 8 bit register it would be an overflow

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5
Q

What is the effect of a left logical binary shift?

A

It will multiply a binary number by 2

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6
Q

What is the effect of a right logical binary shift?

A

It would divide the binary number by 2

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7
Q

How would you convert -21 to binary?

A

Work out the positive binary equivalent of -21, 0001 0101
Flip all the bits 1110 1010
Add one 1
Convert: 1110 1011

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8
Q

How would you convert the negative two’s complement binary number 1110 1110 to denary?

A

Flip the bits 0001 0001
Add one 1
Convert: -0001 0010 =-18

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9
Q

What is a character set?

A

A set which consists of all the letters, numbers, and characters that can be recognised by a computer system

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10
Q

How many bits and characters are in the ASCII Character Set?

A

7 bits, 128 characters

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11
Q

How many bits and characters are in the Extended ASCII Character Set?

A

8 bits, 256 characters

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12
Q

How many bits and characters are in the Unicode Character Set?

A

16 bits, 65,356 characters
(enough to represent most of the characters in international languages like Russian, Chinese & Arabic + emojis)

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13
Q

What is the sample resolution?

A

The number of bits per sample

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14
Q

What is the sample rate?

A

The number of samples taken in a second

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15
Q

How do you calculate sound file size

A

Length of sample in seconds × Sample Rate × Sample Resolution

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16
Q

What affects the quality of the recorded sound and the file size of the recording

A

How often the height is recorded (the sample rate or frequency)
The accuracy to which the height is recorded (the bit depth or sample resolution)
The duration of the recording

17
Q

What is the sample rate measured in?

A

Hertz, Hz

18
Q

What increases the file size?

A

More samples and longer duration

19
Q

What is the colour depth?

A

The number of bits used to represent each colour

20
Q

What is the colour depth if there were 2 colours in the pixel image

A

1 bit per pixel

21
Q

What is the colour depth if there were 4 colours in the pixel image?

A

2 bits per pixel

22
Q

What is the colour depth if there were 8 colours in the pixel image?

A

3 bits per pixel

23
Q

What is the colour depth if there were 16 colour in the pixel image?

A

4 bits per pixel

24
Q

What is the relationship between the colour depth and the quality of an image?

A

As the colour depth increases, so does the quality of the image

25
Q

How do you calculate the file size of an image?

A

width in pixels × height in pixels × colour depth
(Dividing by 8 will give the size in bytes)

26
Q

How does the density of the pixels affect the image?

A

It affects the sharpness of an image
More pixels per inch will smooth the edges and improve the overall quality
This increases the size of the image file, making it possible to enlarge the image without a visible loss to quality

27
Q

What is compression used for?

A

Reduces the size of a file on a disk and of large files sent by email where there are maximum attachment limits

28
Q

What are the formats of lossy compression?

A

JPG, MP3, WMV, MPG

29
Q

What are the formats of lossless compression?

A

TIF, PDF, GIF, PNG, ZIP

30
Q

What are the advantages of lossy compression?

A

Smallest file sizes
Least transmission time
Reduces Internet traffic & collisions

31
Q

What are the disadvantages of lossy compression?

A

Detail is permanently lost by reducing the colour depth, resolution or sample rate

32
Q

What are some uses of lossy compression?

A

Music streaming
Online images & videos
Image libraries on devices
In the cloud

33
Q

What are the advantages of lossless compression?

A

Original quality is preserved so no information or data is lost

34
Q

What are the disadvantages of lossless compression?

A

Less significant reduction in file size

35
Q

What are some uses of lossless compression?

A

Text documents
Electronic books
High resolution print documents

Computer Science IGCSE (5 decks)

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