Data Representation

Question 1

What do computers use to show the flow of electricity?

Answer 1

binary digits, 1 and 0

Question 2

As a binary digit, what does 1 mean?

Answer 2

electricity is flowing

Question 3

As a binary digit, what does 0 mean?

Answer 3

electricity is not flowing

Question 4

What is a bit and its unit?

Answer 4

‘b’, a single binary digit = 1 or 0

Question 5

What is a nibble?

Answer 5

4 bits

Question 6

What is a byte and its unit?

Answer 6

‘B’, 8 bits

Question 7

What is a Kilobyte and its unit?

Answer 7

‘kB’, 1000 bytes

Question 8

What is a Megabyte and its unit?

Answer 8

‘MB’, 1000 kilobytes

Question 9

What is a Gigabyte and its unit?

Answer 9

‘GB’, 1000 megabytes

Question 10

What is a Terabyte and its unit?

Answer 10

‘TB’, 1000 gigabytes

Question 11

What is a Petabyte and its unit?

Answer 11

‘PB’, 1000 terabytes

Question 12

How many values can a nibble take?

Answer 12

2^4 = 16 values

Question 13

How many values can a byte take?

Answer 13

2^16 = 256 values

Question 14

What shift do you do to multiply a binary number?

Answer 14

LEFT shift = every place shifted left means the number is doubled

Question 15

What shift do you do to divide a binary number?

Answer 15

RIGHT shift = every place shifted to the right means the number is halved

Question 16

How are images stored?

Answer 16

as pixels - bitmap images - the colour of each pixel is represented by binary code so the number of colours available relates to the number of bits the code has

Question 17

Black and White=

Answer 17

1 bit image, 1 bit for each pixel (eg: 0 = white and 1 = black)

Question 18

To make greater range of shades…

Answer 18

increase the number of bits for each pixel

Question 19

How do you calculate file size?

Answer 19

file size (in bits) = width x height x colour depth ( or = image resolution x colour depth)

Question 20

What does image resolution mean?

Answer 20

the number of pixels in the image so the higher the image resolution, the higher the quality and the number of pixels

Question 21

What does colour depth mean?

Answer 21

the number of bits used for each pixel

Question 22

Using the colour depth, how do you calculate the number of colours that can be made?

Answer 22

total number of colours = 2^n (where n = number of bits per pixel = (bpp)

Question 23

What is metadata and why is it needed?

Answer 23

devices need metadata to display the images, its the information stored in the image file that helps the computer recreate the image

Question 24

What does metadata normally include?

Answer 24

the images file format, height, width, colour depth and resolution

Question 25

What is meant by an analogue signal?

Answer 25

sound is recorded by a microphone as an analogue signal which are pieces of continually changing data

Question 26

What are analogue signals converted into and why?

Answer 26

digital data so that computers can read and store sound files

Question 27

What are the sound converters called?

Answer 27

analogue to digital converters

Question 28

Whats the process of converting analogue to digital called?

Answer 28

sampling

Question 29

What fa actors affect the size and quality of sound files?

Answer 29

sample rate and bit depth

Question 30

What is sample rate?

Answer 30

sampling frequency, how many samples you take in a second (Hz or kHz)

Question 31

What is a common sample rate?

Answer 31

44,100 samples per second, 44.1 kHz

Question 32

What is bit depth?

Answer 32

number of bits available for each sample

Question 33

How do you calculate the size of a sound file?

Answer 33

file size (in bits) = sample rate (Hz) x bit depth x duration (seconds)

Question 34

What would increasing the sample rate do?

Answer 34

better quality sample sound and more closely match the original recording because the analogue recording is sampled more often

Question 35

What would increasing the bit depth do?

Answer 35

the digital file will pick up quieter sounds so the sampled sound will be closer to the quality of the original recording

Question 36

What is data compression?

Answer 36

making files smaller while trying to keep them as true to the original

Question 37

What are the uses of data compression?

Answer 37

less storage space, web pages can load quicker in web browsers, streaming and downloading files from the internet is quicker because they take up less bandwidth, email services usually have size restrictions so compressing means you can still send it

Question 38

What are the two types of data compression?

Answer 38

lossy and lossless

Question 39

How does lossy compression work?

Answer 39

permanently removes data from the file - limits the number of bits the file needs so reduces its size

Question 40

How does lossless compression work?

Answer 40

temporarily removes data from the file to store it and restores it to its original stake when its opened

Question 41

Pros of lossy compression?

Answer 41

greatly reduces file size, lossy files take up less bandwidth, commonly used so software can read it, quicker to download and stream

Question 42

Cons of lossy compression?

Answer 42

permanently loses data, can't be used on text or software files because they need to retain all information, worse quality however it is barely noticeable

Question 43

Examples of lossy file types:

Answer 43

MP3 (audio), AAC (audio), JPEG (image)

Question 44

Pros of lossless compression?

Answer 44

no reduction in quality, can be decompressed, can be used on text and software files

Question 45

Cons of lossless compression?

Answer 45

only a slight reduction in file size

Question 46

Examples of lossless file types:

Answer 46

FLAC (audio), TIFF (image), PNG (image)