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AS Level CS 9618 Paper 1 > information rep and multimedia > Flashcards

information rep and multimedia Flashcards

1
Q

analogue data

A
  • data obtained by measurement of physical property
  • any value from a contiuous range of values
  • continuous electrical signals
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2
Q

ASCII

A
  • only english alphabets can be represented
  • each character encoding takes up 7 bits, 128 possible characters
  • smaller storage space
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3
Q

bandwidth

A

rate of data transfer

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4
Q

Binary coded decimal (BCD)

A

practical applications:
- a string of digits on any electronic device displaying numbers (calculators)
- accurately measuring decimal fractions
- electronically coding denary numbers

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5
Q

bitmap images

A

images stored as an array of individual pixels. a bitmap image is created by combining pixels.

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6
Q

colour depth/bit depth

A

number of bits allocated to represent each pixel’s colour -> colour depth depends on bit depth

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7
Q

compression

A

the reduction of file size

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8
Q

digital data

A
  • data that has been stored as binary value (0s and 1s)
  • discrete electrical signals
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9
Q

drawing list

A

set of commands defining the vector

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10
Q

drawing objects

A

a mathematically defined construct of shapes

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11
Q

Extended ASCII

A
  • includes most European languages’ alphabets
  • extended to 8 bits, 256 possible characters
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12
Q

features of vector graphics

A
  • stores a set of instructions about how to draw the shape
  • individual elements of vector graphics can be grouped
  • each geometric shape needs to be changed to alter the design
  • does not require a large file size
  • not very realistic as the number of shapes are limited
  • file formats: .svg, .cgm, .odg
  • can be resized without pixelation
    storing commands, not individual pixels
  • can be transferred and downloaded quicker
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13
Q

features or graphic editing software

A

Ready Crabs Bring Revenge
- re-size: increase/decrease the size of the image
- crop: remove certain parts of the image
- blur: reduce the focus
- red-eye reduction: reduces red light reflected from human eye

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14
Q

file header

A

contains info regarding the image such as image size, number of pixels, types of compression, colour depth, file location

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15
Q

formula for bit rate

A

bit rate = sampling rate x sampling resolution
file size = bit rate x length of sound

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16
Q

formula for size calculation

A

width pixels x height pixels x colour depth

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17
Q

hexadecimal base and applications

A

base 16
- defining colours in HTML
- defining media access control (MAC) addresses
- assembly language and machine code
- debugging via memory dumps

18
Q

high resolution images -> increase in file size

A

impacts:
- the number of images that can be stored on the hard drive
- the time to download images from the internet
- the time it takes to transfer images from device to device

19
Q

how images are encoded into digital format

A
  • images are stored as bitmap images
  • each image is made up of pixels
  • each pixel is of a single colour
  • each colour has a unique binary number
  • sequence of binary numbers is stored in each image
20
Q

how sampling is used to record the sound clip

A
  • amplitude of sound wave is determined
  • at set time interval
  • to get an approximation of the sound wave
  • encoded as a sequence of binary numbers
  • increased sampling rate will improve the accuracy of the recording
21
Q

image resolution

A
  • measured in pixels per inch, value determines the amount of detail an image has
  • high image resolution means that there are more pixels per inch, resulting in more pixel info and creating high quality images
22
Q

lossless compression

A
  • data is not lost
  • file can be decompressed as the original
23
Q

lossless is used when

A

accuracy of data is important

24
Q

lossy file compression

A

data is lost and the decompressed file is not the same as the original

25
Q

lossy is used when

A
  • accuracy of data is unimportant
  • smaller file size is needed
  • for sound files (.mp3), .jpeg images
  • sound files compression utilizes perceptual coding to remove certain parts (frequencies) of sound that are less audible to human hearing
26
Q

media access control (MAC) address

A

every device on a network has a MAC address which identifies it uniquely. data packets sent to switches will have a MAC address identifying the source of the data

27
Q

metadata

A

data/information about data
e.g: file name, file format, colour depth

28
Q

modifying image resolution

A
  • pixels can be removed to fit the screen
  • instead of modifying, simply zoom in to enlarge it to full-screen size; causes image to become pixelated as the pixel density is reduced and can cause image quality to become deteriorated
29
Q

pixel

A

smallest picture element

30
Q

pixel density

A

number of pixels per square inch

31
Q

property

A

data about the shapes

32
Q

quantization error

A

the difference between the analogue signal and the closest digital value at each sampling instant

33
Q

reasons why files need to be compressed

A
  • data files can be very large
  • it would take a long time to transfer the non compressed file / compressed files will download faster
  • a higher bandwidth would need to transmit the uncompressed file
34
Q

run length encoding (RLE)

A
  • looks for runs of consecutive pixels of the same colour
  • then reduces file size of a sequence of elements with adjacent and identical elements
  • stores the colour value once and the number of times it occurs
  • lossless
35
Q

sampling

A

taking measurements of sound at regular time intervals

36
Q

sampling rate

A

number of samples taken per second
higher sampling rate -> higher accuracy

37
Q

sampling resolution

A

number of bits used to store each sample

38
Q

screen resolution

A

number of pixels which can be viewed horizontally and vertically on the screen
- if screen res < image res, the whole image cannot be shown on the screen or the original image will be a lower quality

39
Q

true colour

A

requires 3 bytes per pixel which gives more than one million colours

40
Q

Unicode

A
  • superset for ASCII + extended ASCII - recognised by various global languages
  • greater range of characters, as it uses 2 or 4 bytes per character
  • 2 or 4 times more storage space per char
41
Q

vector graphics

A

images made up of drawing objects, the properties of each object determine its shape and appearance

42
Q

perceptual coding

A

used to remove certain parts (frequencies) of sound that are less audible to human hearing

AS Level CS 9618 Paper 1 (9 decks)

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