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Computer science > 1.2 - Data Representation > Flashcards

1.2 - Data Representation Flashcards

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1
Q

What is a ‘Bit’

A

A single binary digit, a Zero or a One

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2
Q

What is a ‘Nibble’

A

4 bits

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3
Q

What is a ‘Byte’

A

8 bits

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4
Q

What is a ‘Kilobyte’

A

1,000 bytes or 8,000 bits

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5
Q

What is a ‘Megabyte’

A

1,000,000 bytes

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6
Q

What is a ‘Gigabyte’

A

1,000,000,000 bytes

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7
Q

What is a ‘Terabyte’

A

1,000,000,000,000 bytes

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8
Q

What is a ‘Petabyte’

A

1,000,000,000,000,000 bytes

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9
Q

Why is everything in a computer system stored in binary

A

easier to process
cheaper to manufacture electronic components with just two states
more reliable

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10
Q

What can you represent when you combine a series of bits

A

Any kind of data:

  • texts
  • images
  • sounds
  • commands
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11
Q

How do you calculate the size of a text file

A

Bits per character X Number of characters

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12
Q

How do you calculate the size of a sound file

A

Sample rate X duration (s) X Bit depth

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13
Q

How do you calculate the size of an image file

A

Colour depth X Image height (Px) X Image width (Px)

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14
Q

What kind of system is binary

A

Base 2, this means only ones and zeros are used. 1 2 4 8 16 32 64 128

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15
Q

Addition - What are the four rules for adding binary numbers

A
  • 0 + 0 = 0
  • 0 + 1 = 1
  • 1 + 1 = 0 (carry a 1)
  • 1 + 1 + 1 = 1 (carry a 1)
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16
Q

What is it called when you reach the end and still have to carry a 1

A

an overflow error, it is when the one we have to carry has gone beyond the capacity of the current storage line.

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17
Q

What is the highest number that can be stored in 8-bit binary

A

255

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18
Q

What numbers can be represented in hexadecimal

A

0-15

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19
Q

What are hexadecimal numbers used for?

A

Representing colours, memory addresses, and Mac Addresses

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20
Q

Why are hexadecimal numbers useful

A

can represent large binary numbers in a smaller number of digits

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21
Q

How do you convert denary to hexadecimal

A
  • convert denary to binary
  • group binary timeline into two sets of nibbles
  • add each of the nibbles where there are 1’s
22
Q

What is numbers 10-15 in hexadecimal

A 
10-A
11-B
12-C
13-D
14-E
15-F
23
Q

What is a binary shift

A

When you move the binary values to the left or right

24
Q

What is the effect of a one bit left binary shift

A

Multiplication of 2

25
Q

What is the effect of a one bit right binary shift

A

Division of 2

26
Q

What happens at a two bit shift

A

Multiplication of division of 4

27
Q

text - What is a character set?

A

a defined list of characters recognised by the computer. Each character is represented by a single number

28
Q

text - How is each character represented

A

by a unique binary number

29
Q

tex - What is ASCII

A

A 7-bit character set
2^7 characters 128
8th bit is a check digit

30
Q

text - What is Extended ASCII

A

An 8-bit character set

2^8 = 256

31
Q

text - What is Unicode

A

A 24-bit character set
2^24 ≈ 16 million
includes every character from every written language

32
Q

images - What two different ways can images be stored

A

Bitmaps or Vectors

33
Q

images - What are bitmaps constructed of

A

Pixels

34
Q

images - What decides the number of bits required for each pixel

A

How many colours are needed

35
Q

images - how is the number of colours calculated

A

2^n. where n is the number of bits for each pixel

36
Q

images - What is the Colour Depth

A

The number of bits used to store each pixel

37
Q

images - What is metadata and what does it include

A

Additional data about the file: file type, date created, author
Additional data about the image data: height and width, resolution, colour depth

38
Q

images - What effect does colour depth have on the quality and size of an image file

A

higher the colour depth, the more colours can be stored, so higher quality. because when you increase the colour depth you are increasing the number of bits used to store each pixel, you are increasing the file size

39
Q

images - What is the resolution of an image?

A

The number of pixels in an image

40
Q

images - How does resolution effect the quality and file size of an image

A

higher resolution means more pixels so more detailed image. also it increases the file size

41
Q

images - What colour depth are most photos stored in?

A

24-bit

42
Q

sound - What is the sample rate

A

How often per second you record the amplitude of a sound wave. How many samples are taken per second

43
Q

sound - what is the bit depth

A

number of bits in each sample. the higher the more accurate the sample

44
Q

sound - what is the bit rate

A

number of bits stored for each second of audio

45
Q

sound - how does the sample rate effect the quality and size of audio

A

Increases quality as you are recording the amplitude more often so it will be a smoother playback.
increases file size as more samples are taken per second

46
Q

sound - how does the bit depth effect the quality and size of audio

A

Increases quality as more bits are used to store each sample.
increases file size as more bits are used to store each sample

47
Q

compression - What does compression do

A

reduces the number of bits in a file, so making the size of the file smaller

48
Q

compression - Why is compression useful

A

makes files smaller
more data can be stored on a storage device
makes data transfer faster

49
Q

compression - lossy compression?

A

Where some data cannot be recovered. greatly reduces file size. reduces quality of file.

50
Q

compression - lossless compression?

A

none of the data is lost, its encoded differently. can be turned back to original format. doesn’t reduce file size as much as lossy. can be used on all types of data

51
Q

compression - What is lossy compression most suitable for?

A

images, sound, video

52
Q

compression - What is lossless compression most suitable for?

A

documents and executable files

Computer science (2 decks)

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