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Comp sci > Chap 1 - Data representation (no. systems, [text, sound, video, image], [data storage and file compression]) > Flashcards

Chap 1 - Data representation (no. systems, [text, sound, video, image], [data storage and file compression]) Flashcards

1
Q

name the number systems

A

-binary
-hexadecimal
-Octal
-denary

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2
Q

note: sequence for 2 powers starts form 1

A
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3
Q

what are the bases for the number systems

A

-binary - 2
-hexadecimal -16
-Octal - 8
-denary- 10

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4
Q

numbers in Hexadecimal

A

0 to F

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5
Q

numbers in octal

A

0 - 7

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6
Q

numbers in denary

A

0 - 9

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7
Q

numbers in binary

A

0 - 1

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8
Q

what does 1 mean in binary

A
  • ON, TRUE, HIGH
  • flow of electrical signals
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9
Q

what does 0 mean in binary

A
  • OFF, FALSE, LOW
  • absence of flow of electrical signals
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10
Q

sequence for binary until 2^13

A

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192

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11
Q

what are numbers in binary called

A

bit

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12
Q

what is Least significant bit (LSB)

A

bit on the extreme right

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13
Q

what is Most significant bit (MSB)

A

bit on the extreme left

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14
Q

what is assigned to each bit

A

index value

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15
Q

what does index value start and end with

A

0 until MSB in denary

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16
Q

how do you go binary to denary

A
  • use sequence
  • multiply the 1 bit by 2 to the power of its index value. and add values
    eg, 101 - 1x2^0 + 1x2^2 = 5
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17
Q

how do you go denary to binary

A

-divide number by 2 until you get 0
-track remainders and take from bottom to top
eg, 2| 12 0
2| 6 0
2| 3 1
2|1
0
9 = 1100
-bottom will be MSB

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18
Q

how do you go from binary to hexadecimal

A

-group bits into groups of 4 starting from LSB
-add 00 at MSB to complete groups
-convert each group to hexadecimal
-write the numbers starting from MSB group
eg. 0001 1010 = 1A
1 A (hexadecimal)
-MSB no. will start

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19
Q

how do you go binary to ocotal

A

-group bits into groups of 3 starting from LSB
-add 00 at MSB to complete groups
-convert each group to denary
-write the numbers starting from MSB group
eg. 001 010 = 12 - octal
1 2 (denary)
-MSB no. will start

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20
Q

how do you go from octal to binary

A

-write the binary bits for each octal digit

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21
Q

how do you go from hexadecimal to binary

A

-write the binary bits for each hex digit

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22
Q

the bits for hex 9 - F

A

hex - binary - denary
9 - 1001 |9
A - 1010 |10
B - 1011 |11
C - 1100 |12
D - 1101 |13
E - 1110 |14
F - 1111 |15

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23
Q

number systems conversion algorithms

A

Hex
|
Octal - Binary - Denary
H - B - 1 digit = 4 bits
O - B - 1 digit = 3 bits
D - B - divide by 2
B - D - sequence

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24
Q

why is binary used in computers

A

-computers are made up of logic gates
-which only have 2 states (0 or 1)

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25
Q

why is hex used over binary by users

A

-easier to read/ identify errors because it shortens binary
-takes less screen space
-less chance of making an error

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26
Q

5 uses of Hex

A

-MAC address
-IP address
-HTML colour codes
-Error code / memory dump
-ASCII

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27
Q

what does MAC address stand for

A

Media Access Control

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28
Q

what is error codes

A

locate error

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29
Q

what does Ox and Ob mean in error codes

A

Ox - hex
Ob - binary

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30
Q

What is HTML colour codes

A

Hypertext Markup Language colour codes
-represent colour on screen
-diff. values = diff. colours
-intensity of colour depends on Hex value
-primary colours: RGB - Red, Green, Blue
eg. # FF FF FF - white
# 00 00 00 - black

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31
Q

what is ASCII

A

American Standard Code for Information Interchange
-unique 7 bit values for characters on standard keyboard
-base 256, 0 - 255
Unicode
-support all languages
-up to 4 byte per character
-overlaps first 128 character with ASCII
-Extended ASCII
-1 byte (8 bits) for non-English characters

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32
Q

how do you add or subtract binary

A

two’s complement

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33
Q

rules for two’s complement

A
  • 0 + 0 = 0
  • 0 + 1 = 1
  • 1+ 0 = 1
  • 1 + 1 = 10 (move 1 to other side)
  • 1+ 1 + 1 = 11
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34
Q

note: when asked to find 2’s complement of a number, just do 2’s complement - find the other value

A
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35
Q

what does each binary value have

A

a positive and negative number

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36
Q

how to find two’s complement of a number

A

-find the first 1 from the LSB and flip the bits beyond it

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37
Q

how to convert two complement bit (negative bit) into denary

A

-find value of first 1 from MSB & make it negative
-add negative no. with the values of the other 1 bits
eg. 10100011 is a two’s complement integer
-128 + (1+2+32) = -93

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38
Q

what does you call when there is an extra number when doing two’s complement addition

A

carry
eg. 10100 + 10001 = 100101
| this 1 is overflow

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39
Q

how do you add binary

A

add the number using the two’s complement rules

40
Q

how do you subtract binary

A

-convert the subtracting number to negative by finding the first 1 from LSB and flipping the other numbers
-add the numbers
-if answer is supposed to be negative flip the binary result
-if there
eg. 0111 - 1010 (7 - 10)
(10) 1010 - (-10) 0110
0111 + 0110 = 1101 -> - 0011 (flipped)
(7 + (-10) = -3)
-make both no. same no. bits first

41
Q

why does overflow error happen

A

-when the binary value is larger than the __ bit register
-so all the bits required to represent the value cannot fit

42
Q

how to do multiplication and division

A

logical binary shifts

43
Q

which direction is multiplication and division in logical binary shift

A

multiplication - left
division - right

44
Q

what is each shift in logical binary shift worth

A

an power of 2

45
Q

how do you do logical binary shifts

A

add a 0 to MSB or LSB based on multiplication or division

46
Q

what will happen when computers don’t have enough bits to store date from logical shift

A

error message

47
Q

define a bit

A

smallest unit of data a computer can process

48
Q

define bitmap

A

image made up of 2D matrix pixels

49
Q

define pixel

A

single element of a bit-map image

50
Q

define colour depth

A

no. bit allocated for each colour

51
Q

define image resolution

A

number of pixels required for an image

52
Q

define screen resolution

A

number of pixels on a screen

53
Q

are file size and image size the same

A

yes

54
Q

what is image size/ file size

A

total bits needed for an image

55
Q

how to get file size for image

A

colour depth x image resolution

56
Q

what happens when you increase colour depth or image resolution

A

file size increases

57
Q

variables when finding file size of image

A

-colour depth
-image resolution

58
Q

define sample resolution

A

number of bits allocated for each sample

59
Q

variable when finding file size of sound

A

-sample resolution
-sample rate
-audio size

60
Q

define sample rate

A

number of samples collected per second

61
Q

define audio size

A

length of sound

62
Q

what happens when you increase sample resolution or sample rate or audio size

A

file size increases

63
Q

how to get file size for sound

A

sample rate x sample resolution x audio size

64
Q

what must sample rate be

A

consistant

65
Q

benefits of increased variables for sound

A

-larger dynamic sound
-better faithful sound quality
-less sound distortion

66
Q

drawbacks of increased variables for sound

A

-produce larger files
-longer to transmit or download file
-require greater processing power

67
Q

how to compress an image

A

-reduce colour depth
-reduce image resolution

68
Q

how to compress an audio

A

-reduce sample rate
-reduce sample resolution

69
Q

2 types of file compression

A

-lossy
-lossless

70
Q

what is lossy compression

A

-compression algorithm removes unnecessary data from the original file
-original file cannot be reconstructed once compressed

71
Q

what is lossless compression

A

-reduces file size without removing any information
-original file can be reconstructed once decompressed

72
Q

describe how lossy compression reduces file size in a video

A

-uses compression algorithm
-reduntant data is removed
-reduce: colour depth, image resolution, sample rate, sample resolution, frame rate
-use perceptual music sharpening
-data is permanently removed

73
Q

reasons to use lossy over lossless

A

-more decreases file size
-less storage space on computer
-quicker to download/ upload
-may not need to be high quality
-website will load faster for user
-less lag/ buffering when watching (video)
-use less data allowance

74
Q

what does lossy do to images

A

decreases image resolution, colour depth and crop image

75
Q

3 lossy compression algorithms

A

-JPEG
-MPEG-3
-MPEG-4

76
Q

what is done when there is perceptual music sharpening

A

-decrease sample rate
-decreases sample resolution
-remove frequency outside of human hearing
-remover softer sounds

77
Q

what is the human hearing range

A

20Hz - 20 000Hz

78
Q

what is the size reduced by perceptual music sharpening

A

90%

79
Q

how does JPEG do lossy

A

-reduce colour depth
-separate pixel colour from brightness - allows some data to be distorted

80
Q

how does MPEG-3 do lossy

A

-use perceptual music sharpening

81
Q

how does MPEG-4 do lossy

A

-extended version of MPEG-3
-reduce sound quality, image quality, frames per second

82
Q

3 lossless algorithms

A

-GIF
-PNG
-RLE

83
Q

what is RLE

A

-Run Length Encoding
-reduces size of identical and adjacent string data
-first repeated strong is encoded with no. identical data items and code of data item- respectively

84
Q

what compression does text, image, audio and video data use

A

-text: lossless
-audio: lossy
-image: lossy, lossless
-video: lossy, lossless

85
Q

how is RLE used for text data

A

eg. aaa aa - 05 97
05 - number of identical data items
97 - ASCII code for “a”
-it changed from 5 bits to 4 bits

86
Q

How is RLE used for image data

A

eg. 2 black, 1 white, 3 black (image)
-go with 1 colour and change it when the next one comes
02 00 00 00
02 - number of times
00 00 00 - code of colour

87
Q

2 memroy conversion style

A

-Binary
-Denary

88
Q

3 reasons to reduce file size

A

-shorter time to transmit file
-shorter time to download/ upload file
-less storage space

89
Q

what is a byte worth

A

8 bits

90
Q

what is half a byte called

A

nibble

91
Q

write the names for binary style memory conversion

A

-Bits
-Byte
-Kibibytes (Kib)
-Mebibytes (Mib)
-Gibibytes (Gib)
-Tebibytes (Tib)
-Pebibytes (Pib)
-Exibibytes (Eib)

92
Q

what is the conversion between bits and byte

A

2^3

93
Q

what is the conversion except bit to byte in binary memory conversion

A

2^ 10 = 1024

94
Q

if go from bottom in memory conversion:
if go from top in memory conversion

A

-multiply
-divide

95
Q

write the names for denary style memory conversion

A

-Bits
-Byte
-Kilobytes (KB)
-Megabytes (MB)
-Gigabytes (GB)
-Terabyte (TB)
-Petabyte (PB)
-Exabyte (EB)

96
Q

what is the conversion except bit to byte in denary memory conversion

A

10^3 = 1 000

Comp sci (13 decks)

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