Fundamentals of Data Representation

Question 1

Why is a relative error more important than an absolute error?

Answer 1

The effect of an error depends on its size relative to the number that is represented

Question 2

What is a character code?

Answer 2

A character code uses a unique number to represent each character

Question 3

Advantages of using MIDI (3 marks)

Answer 3

1. no loss of data about musical notes
2. easy to modify
3. more compact representation

Question 4

Why do vector graphics use less memory than bitmap graphics (3 marks)

Answer 4

1. vector graphics don’t store the colour of each pixel
2. vector graphics store properties of the objects that an image is composed of
3. only takes a small amount of memory to store properties of an object

Question 5

Steps of an ADC: 3 marks

Answer 5

analogue signal is sampled at regular intervals
amplitude of each wave/sample is measured
each sample measurement is coded in binary

Question 6

Advantages and disadvantages of vector graphics compared to bitmap graphics: (6 marks)

Answer 6

• image can be scaled without a loss in quality
• vector graphics typically use less storage
• best to use vector graphics when representing logos
• vector graphics can’t represent images not composed of regular/geometric shapes
• can’t easily represent images with areas of changing colours
  -best to use bitmap graphics when representing photographs

Question 7

how is a digital image captured by a camera and compressed using RLE? 6 marks

Answer 7

-light enters through lens
-each sensor produces an electrical current
- signal represents a pixel
-ADC converts measurements of light intensity into binary
-image is analysed to identify runs
-count and a colour of pixels is stored