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computing > unit 3 - data representation > Flashcards

unit 3 - data representation Flashcards

1
Q

what is binary?

A

a base 2 system of numbers using only 1 and 0

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2
Q

what is 1 bit?

A

a 0 or 1

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3
Q

what is 1 byte?

A

8 bits

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4
Q

what is a kilobyte?

A

1000 bytes

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5
Q

what is a megabyte in kB?

A

1000 kB

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6
Q

what is a gigabyte in mB?

A

1000 mB

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7
Q

what is a terabyte in GB?

A

1000 GB

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8
Q

what is a petabyte in TB?

A

1000 TB

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9
Q

what are the uses of binary?

A

it is used to store numbers and do binary arithmetic with

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10
Q

what does a binary shift to the right represent?

A

dividing by 2 - moves all the bits one place to the left

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11
Q

what does a binary shift to the left represent?

A

multiplying by 2 - moves all the bits one place to the right

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12
Q

what is an overflow error?

A

when the result of a binary arithmetic calculation is too long for a computer to process

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13
Q

what are the possible states of binary?

A

256, 128, 64, 32, 16, 8, 4, 2, 1

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14
Q

what is the most significant bit?

A

the bit with the largest value - furthest to the left

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15
Q

what is the least significant bit?

A

the bit with the smallest value - furthest to the right

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16
Q

how to convert binary (0001 1100) to decimal

A

example:

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

16 + 8 + 4 = 28

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17
Q

what is the largest number that can be held in 8 bits?

A

numbers between 0 (0000 0000) and 255 (1111 1111)
2^8 - 1 = 255

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18
Q

what is hexadecimal?

A

a base 16 number system, 0-9 A-F

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19
Q

how many values can be held in hex?

A

256 values - from 0 - 255

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20
Q

what are the advantages of using hexadecimal?

A
  • simpler to remember
  • quicker to type
  • fewer digits so less error prone
  • easier to convert between hex and decimal
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21
Q

hexadecimal (2A) to decimal conversion

A

2 (comes in groups of 16s) + A (10 in hex)
(2 x 16) + 10 = 42 in decimal

multiply left hand digit by 16 and then add the units

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22
Q

decimal (18) to hex conversion

A
  • divide the decimal by 16 to get the number of 16s (left had digit) -> 18/16 = 1 r 2
  • the remainder is the units -> 2
  • the hex value for decimal 18 is 12
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23
Q

binary (1110 0101) to hex conversion

A
  • divide the binary into two niblle of 4 bits
    1110 0101
  • convert each nibble into a decimal and then into its hex value and rejoin
    1110 = 14 = E + 0101 = 5 = 5 in hex
  • so 1110 0101 = E5 in hex
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24
Q

hex (3B) to binary conversion

A
  • split the two hex characters and convert to binary
    3 = 0011 B = 1011
  • so 3B = 0011 1011
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25
Q

what are the rules of binary addition?

A
  • 0 + 0 = 0
  • 0 + 1 = 1
  • 1 + 0 = 1
  • 1 + 1 = 0 carry the 1
  • 1 + 1 + 1 = 1 carry 1
  • 1 + 1 + 1 + 1 = 1 carry the 1 over two columns
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26
Q

what is ASCII?

A

a code for representing english characters with numbers with each character being represented with a binary number
it includes: numbers 0-9, upper and lowercase A-Z, punctuation symbols and the space character

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27
Q

how many characters can be held in 7-bit ASCII?

A

128

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28
Q

what is a character set?

A

a set of letters, symbols and digits that can be represented by a computer

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29
Q

what are two examples of character sets?

A

ASCII and unicode

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30
Q

what can a computer’s memory and storage only hold?

A

can only hold binary 1s and 0s

31
Q

how many characters can be encoded in extended ASCII?

A

256 different characters because it is 8 bit

32
Q

what is unicode?

A

it represents other characters from different languages so it has been developed to use 16 bits - 65, 536 combinations

33
Q

what is a pixel?

A

a picture element - the smallest identifiable area of an image.

34
Q

what is the function of a pixel?

A

each pixel is given a single colour and is given a binary value, which represents the colour.
a pixel’s colour can be changed by changing this value

35
Q

what is a bitmap?

A

an image composed of pixels with a fixed resolution

36
Q

what is the colour depth?

A

the number of bits per pixel

37
Q

what does an increase in colour depth mean?

A

it means that more bits are used to represent each pixel so the overall size will increase

38
Q

what is the equation to calculate file size in bytes?

A

(image width x image height x colour depth) / 8

39
Q

what is the equation to calculate file size in bits?

A

image width x image height x colour depth

40
Q

what is the image resolution?

A

the concentration of pixels within a specific area- defined by image width and height in pixels

41
Q

what does a higher amount of pixels in a given area mean for the image?

A

higher imagine resolution so the quality of the image will be better

42
Q

what does the size of the image depend on?

A

the number of pixels

43
Q

what does having more pixels per inch mean for the image?

A

the image is sharper but the file size is higher

44
Q

what are some bitmap image file formats?

A

GIF, JPG, PNG

45
Q

how can we find colour depth?

A

pixel = n bits
combinations = 2^n

46
Q

what are the colour values of individuals expressed as and why?

A

in software they are represented as decimal RGB values and in hexdecimal - this is because it is easier for people to read, write, remember and reduce errors if copied

47
Q

what do the RGB values range between?

A

0-255

48
Q

what is image metadata?

A

information other than the image data that is stored with a file, including:
- colour depth in bits per pixel
- resolution (height and width in pixels)
- date created
- author

sometimes this the reason why file sizes don’t always add up

49
Q

what is the difference between digital and analogue

A
  • sound waves are measured in analogue which are continuously changed
  • but it must be stored in a digital format, which is discrete
50
Q

what is sampling?

A

soundwaves being measured at regular intervals converting the waveform into a numerical representation - that is how sound is digitised

51
Q

what does a analogue to digital converter do? and why?

A

takes signals and converts them into a digital representation because sound must be converted into a digital form to be stored and processed by a computer

52
Q

what is a sample?

A

a measure of amplitude at a point in time

53
Q

what is sample resolution?

A

the number of bits used to store each sample

54
Q

what do more bits per sample mean for the sound quality and the file size?

A
  • enables the height of the wave to be more accurately measured
  • but also increases file size
55
Q

what is the sample rate?

A

number of samples taken per second
the greater the frequency, the greater the ccuracy and file size

56
Q

what is sample rate measured in?

A

hertz
1Hz = 1 sample per second

57
Q

what is the equation for calculating the file size of a sound file?

A

sample resolution x sample rate x number of seconds

  • divide by 8 to get the answer in bytes
58
Q

what are the common sample rate and resolution for a CD audio?

A

sample rate: 44.1 kHz or 44100 Hz
sample res: 16 bits

59
Q

what is the sample resolution?

A

the number of bits used to record each measurement

60
Q

what is the human hearing rate?

A

20Hz - 20,000Hz

61
Q

what is lossy compression?

A
  • removes unnecessary sounds that we can’t easily hear or that least affect the perceived playback quality
  • it is compressed by removing some detail from the original
62
Q

what are the advantages of lossy?

A
  • you can save lots of storage because lossy can easily compress 10MB into 1MB
  • useful for storing, downloading and streaming
63
Q

what are the disadvantages of lossy

A
  • permanently loses data that can’t be returned and may result in digital artifacts
  • can’t be used on text or software files
  • lose quality on images and audio
64
Q

what is lossless compression?

A

date compression technique in which the files can be reduced by compression but doesn’t not lose any information

65
Q

how does lossless compression work?

A

the algorithm finds groups of repeating data and records the data once along with the number of repetitions

66
Q

what are the benefits of compression?

A
  • smaller files, fewer packets, faster transmission, hence less traffic
  • reduces download times
  • reduces space taken up on a disk/server
  • reduces amount of bits required to store data
67
Q

examples of lossy compression:

A

JPEG, MP3, MP4

68
Q

examples of lossless compression:

A

PNG, ZIP, GIF

69
Q

what is huffman encoding?

A

a form of lossless compression based on certain characters appearing more often than others. it uses the repeated patterns in the original pattern and encodes each pattern in a dictionary

70
Q

what is (RLE) run length encoding?

A

an algorithm to compress data that uses frequency/word pairs to reduced the amount of data stored

71
Q

what is compression?

A

algorithms which reduce file sizes, often used with sound, image and video files

72
Q

what are the two types of compression?

A

lossy and lossless

73
Q

what are digital artifacts?

A

small mistakes that appear on images and videos as a result of lossy compression

computing (10 decks)

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