information rep and multimedia

Question 1

analogue data

Answer 1

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

Question 2

ASCII

Answer 2

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

Question 3

bandwidth

Answer 3

rate of data transfer

Question 4

Binary coded decimal (BCD)

Answer 4

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

Question 5

bitmap images

Answer 5

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

Question 6

colour depth/bit depth

Answer 6

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

Question 7

compression

Answer 7

the reduction of file size

Question 8

digital data

Answer 8

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

Question 9

drawing list

Answer 9

set of commands defining the vector

Question 10

drawing objects

Answer 10

a mathematically defined construct of shapes

Question 11

Extended ASCII

Answer 11

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

Question 12

features of vector graphics

Answer 12

• 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

Question 13

features or graphic editing software

Answer 13

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

Question 14

file header

Answer 14

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

Question 15

formula for bit rate

Answer 15

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

Question 16

formula for size calculation

Answer 16

width pixels x height pixels x colour depth

Question 17

hexadecimal base and applications

Answer 17

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

Question 18

high resolution images -> increase in file size

Answer 18

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

Question 19

how images are encoded into digital format

Answer 19

• 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

Question 20

how sampling is used to record the sound clip

Answer 20

• 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

Question 21

image resolution

Answer 21

• 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

Question 22

lossless compression

Answer 22

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

Question 23

lossless is used when

Answer 23

accuracy of data is important

Question 24

lossy file compression

Answer 24

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

Question 25

lossy is used when

Answer 25

- 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

Question 26

media access control (MAC) address

Answer 26

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

Question 27

metadata

Answer 27

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

Question 28

modifying image resolution

Answer 28

- 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

Question 29

pixel

Answer 29

smallest picture element

Question 30

pixel density

Answer 30

number of pixels per square inch

Question 31

property

Answer 31

data about the shapes

Question 32

quantization error

Answer 32

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

Question 33

reasons why files need to be compressed

Answer 33

- 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

Question 34

run length encoding (RLE)

Answer 34

- 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

Question 35

sampling

Answer 35

taking measurements of sound at regular time intervals

Question 36

sampling rate

Answer 36

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

Question 37

sampling resolution

Answer 37

number of bits used to store each sample

Question 38

screen resolution

Answer 38

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

Question 39

true colour

Answer 39

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

Question 40

Unicode

Answer 40

- 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

Question 41

vector graphics

Answer 41

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

Question 42

perceptual coding

Answer 42

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