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Computer Science > Data Representation > Flashcards

Data Representation Flashcards

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1
Q

What do computers use to show the flow of electricity?

A

binary digits, 1 and 0

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2
Q

As a binary digit, what does 1 mean?

A

electricity is flowing

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3
Q

As a binary digit, what does 0 mean?

A

electricity is not flowing

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4
Q

What is a bit and its unit?

A

‘b’, a single binary digit = 1 or 0

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5
Q

What is a nibble?

A

4 bits

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6
Q

What is a byte and its unit?

A

‘B’, 8 bits

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7
Q

What is a Kilobyte and its unit?

A

‘kB’, 1000 bytes

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8
Q

What is a Megabyte and its unit?

A

‘MB’, 1000 kilobytes

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9
Q

What is a Gigabyte and its unit?

A

‘GB’, 1000 megabytes

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10
Q

What is a Terabyte and its unit?

A

‘TB’, 1000 gigabytes

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11
Q

What is a Petabyte and its unit?

A

‘PB’, 1000 terabytes

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12
Q

How many values can a nibble take?

A

2^4 = 16 values

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13
Q

How many values can a byte take?

A

2^16 = 256 values

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14
Q

What shift do you do to multiply a binary number?

A

LEFT shift = every place shifted left means the number is doubled

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15
Q

What shift do you do to divide a binary number?

A

RIGHT shift = every place shifted to the right means the number is halved

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16
Q

How are images stored?

A

as pixels - bitmap images - the colour of each pixel is represented by binary code so the number of colours available relates to the number of bits the code has

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17
Q

Black and White=

A

1 bit image, 1 bit for each pixel (eg: 0 = white and 1 = black)

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18
Q

To make greater range of shades…

A

increase the number of bits for each pixel

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19
Q

How do you calculate file size?

A

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

20
Q

What does image resolution mean?

A

the number of pixels in the image so the higher the image resolution, the higher the quality and the number of pixels

21
Q

What does colour depth mean?

A

the number of bits used for each pixel

22
Q

Using the colour depth, how do you calculate the number of colours that can be made?

A

total number of colours = 2^n (where n = number of bits per pixel = (bpp)

23
Q

What is metadata and why is it needed?

A

devices need metadata to display the images, its the information stored in the image file that helps the computer recreate the image

24
Q

What does metadata normally include?

A

the images file format, height, width, colour depth and resolution

25
Q

What is meant by an analogue signal?

A

sound is recorded by a microphone as an analogue signal which are pieces of continually changing data

26
Q

What are analogue signals converted into and why?

A

digital data so that computers can read and store sound files

27
Q

What are the sound converters called?

A

analogue to digital converters

28
Q

Whats the process of converting analogue to digital called?

A

sampling

29
Q

What fa actors affect the size and quality of sound files?

A

sample rate and bit depth

30
Q

What is sample rate?

A

sampling frequency, how many samples you take in a second (Hz or kHz)

31
Q

What is a common sample rate?

A

44,100 samples per second, 44.1 kHz

32
Q

What is bit depth?

A

number of bits available for each sample

33
Q

How do you calculate the size of a sound file?

A

file size (in bits) = sample rate (Hz) x bit depth x duration (seconds)

34
Q

What would increasing the sample rate do?

A

better quality sample sound and more closely match the original recording because the analogue recording is sampled more often

35
Q

What would increasing the bit depth do?

A

the digital file will pick up quieter sounds so the sampled sound will be closer to the quality of the original recording

36
Q

What is data compression?

A

making files smaller while trying to keep them as true to the original

37
Q

What are the uses of data compression?

A

less storage space, web pages can load quicker in web browsers, streaming and downloading files from the internet is quicker because they take up less bandwidth, email services usually have size restrictions so compressing means you can still send it

38
Q

What are the two types of data compression?

A

lossy and lossless

39
Q

How does lossy compression work?

A

permanently removes data from the file - limits the number of bits the file needs so reduces its size

40
Q

How does lossless compression work?

A

temporarily removes data from the file to store it and restores it to its original stake when its opened

41
Q

Pros of lossy compression?

A

greatly reduces file size, lossy files take up less bandwidth, commonly used so software can read it, quicker to download and stream

42
Q

Cons of lossy compression?

A

permanently loses data, can’t be used on text or software files because they need to retain all information, worse quality however it is barely noticeable

43
Q

Examples of lossy file types:

A

MP3 (audio), AAC (audio), JPEG (image)

44
Q

Pros of lossless compression?

A

no reduction in quality, can be decompressed, can be used on text and software files

45
Q

Cons of lossless compression?

A

only a slight reduction in file size

46
Q

Examples of lossless file types:

A

FLAC (audio), TIFF (image), PNG (image)

Computer Science (4 decks)

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