data representation

Question 1

What does analogue mean?

Answer 1

continuously changing

Question 2

Why can’t computers store analogue sound?

Answer 2

Because analog sound has infinite data so it’s impossible to store it all.

Question 3

What is the name of the device that takes real world analogue signals and converts them to a digital representation?

Answer 3

Analogue-to-digital converter (ADC)

Question 4

How does a computer convert analogue sound waves to digital sound data?

Answer 4

1) analogue sound is received by a microphone
2) This is converted to an electrical analogue signal
3) The signal amplitude (height of wave) is measured at regular intervals this is called sampling.
4) The values are rounded to a level this is called quantisation
5) The values are stored as a series of binary values

Question 5

What is a sample a measure of?

Answer 5

A sample is a measure of amplitude at a point in time.

Question 6

What are the two things that determine digital sound data’s accuracy?

Answer 6

sample resolution and sample rate.

Question 7

What is sample resolution?

Answer 7

The sample resolution is the number of bits used to store each sample.

Question 8

What is sample rate?

Answer 8

The sample rate is the frequency at which you record the amplitude of the sound i.e the number of samples per second.

Question 9

What is sample rate usually measured in?

Answer 9

Hertz

Question 10

What is the formula to calculate a sound file size?

Answer 10

file size = sample rate x sample resolution x number of seconds

Question 11

What is the sample rate and sample resolution of a cd?

Answer 11

sample rate:44.1kHz

sample resolution: 16 bits

Question 12

What is a vector graphic?

Answer 12

An image made up of lines and shapes with specific properties such as: line style, line colour, fill colour, start point and end point.

Question 13

How does a computer store a photograph taken by a digital camera.

Answer 13

The computer breaks down the image into its smallest elements (pixels).

Question 14

What does pixel stand for?

Answer 14

Picture element

Question 15

What is the size of an image expressed as

Answer 15

Width in pixels by height in pixels e.g 600 pixels x 400 pixels

Question 16

What is the use of pixels in images called?

Answer 16

Bitmap

Question 17

How many possible colours are there in 8 bits per pixel ?

Answer 17

256

Question 18

What is colour depth?

Answer 18

The number of bits per pixel. i.e the number of colours a pixel can be.

Question 19

Why is increasing the colour depth good ?

Answer 19

It makes the image more faithful to how it actually looks

Question 20

What is resolution?

Answer 20

It is how dense the pixels in the image are. i.e How detailed the image looks.

Question 21

What is pixel density measured in?

Answer 21

pixels per inch (PPI)

Question 22

What normally happens when you try to enlarge an image of the internet?

Answer 22

The image goes blurry because the software tries to make up for the pixels that don’t exist

Question 23

What is the normal pixel density of an image off the internet?

Answer 23

72PPI

Question 24

What does file size of an image depend on?

Answer 24

colour depth and the number of pixels in the image.

Question 25

What is the formula for calculating the file size of an image?

Answer 25

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

Question 26

How many bits are used to represent 1 ascii symbol

Answer 26

7 bits i.e A = 0100001

Question 27

what is the advantage of unicode over ascii

Answer 27

unicode represents more characters

Question 28

How many bits in a byte

Answer 28

8

Question 29

what is the order of bits?

Answer 29

kb(1000 bytes), Mb(1000 kb) ,Gb(1000 Mb) , Tb(1000gb)

Question 30

Compress aaabbdddtttyy using run length encoding

Answer 30

3a2b3d3t2y

Question 31

What type of compression is Run length encoding

Answer 31

Lossless

Question 32

How many Binary digits does one hexadecimal digit equal? e

Answer 32

4 bits (e.g F = 1111)