4.5.6 Representing Images, Sound and Other Data

Question 1

Which type of signal is shown by a straight line?

Answer 1

Digital Signal

Question 2

What two things are true of a cipher that is computationally secure?

Answer 2

1. Cipher can be cracked
2. But it cannot be cracked in a reasonable amount of time, given current computational power.

Question 3

What device can be used to convert between Digital and Analogue Sound?

Answer 3

Digital to Analogue Converter (DAC)

Question 4

What device can be used to convert between Analogue and Digital Sound?

Answer 4

Analogue to Digital Converter (ADC)

Question 5

Most Common use for ADC?

Answer 5

To convert sound from Analogue signal to Digital Signal

Question 6

What name is given to the process of reading analogue sound at a fixed interval.

Answer 6

Sampling

Question 7

What is the unit for sampling rate?

Answer 7

Hertz (Hz)

Question 8

State two disadvantages of MIDI

Answer 8

1. Cannot represent speech
2. Sometimes results in less realistic sound than sampled recordings

Question 9

What type of compression is Run Length Encoding

Answer 9

Lossless Compression

Question 10

How much storage in bytes is required to store a 10x10 image with colour depth of 8.

Answer 10

10 x 10 = 100
100 x 8 = 800 bits
800 ÷ 8 = 100 bytes

Question 11

Which type of data is continuous?

Answer 11

Analogue data

Question 12

Give two examples of Metadata for an image

Answer 12

1. Width
2. Height
3. Colour Depth
4. Date Created

Question 13

Which two criteria must be met if a cipher is to use Vernam Cipher?

Answer 13

1. Random
2. At least as long as the plaintext

Question 14

Which type of image can be scaled without a loss in quality?

Answer 14

Vector Graphics

Question 15

Which type of Caesar Cipher is most easily cracked?

Answer 15

Shift Ciphers

Question 16

Which rule states that the sampling rate must be at least twice the length of the signal?

Answer 16

The Nyquist Theorem

Question 17

What does MIDI stand for?

Answer 17

Musical Instrument Digital Interface

Question 18

Two types of compression?

Answer 18

Lossy Compression - Loses less important pieces of data
Lossless Compression - Loses no data

Question 19

How does MIDI store sound?

Answer 19

Using a Series of event messages

Question 20

What type of image is used for storing photographs?

Answer 20

bitmapped graphics

Question 21

With which type of data compression does the image quality stay the same?

Answer 21

Lossless compression

Question 22

Which type of cipher encrypts data by replacing characters?

Answer 22

Caesar Ciphers