1.2.4 - Representing

Question 1

What is a Character Set?

Answer 1

A defined list of characters recognised by the computer, with each character represented by a unique binary number

Question 2

What are the well known character sets? What’re the number of characters that can be represented?

Answer 2

ASCII - 7 bit set - 128
Extended ASCII - 8 bit set - 256
UNICODE - 24 bit set - >16mil

Question 3

How are images stored?

Answer 3

In Binary, as either
Bitmaps :
- Constructed from coloured squares called pixels
- Each pixel of a bitmap is stored in binary
Vectors :
- Stores the maths to draw coloured shape

Question 4

What are the number of bits required for a pixel?

Answer 4

Number required depends on the number of colours
- 1 bit has two values, so 1 bit can store two colours - black or white
- 2 bits have four values, so 2 bits can store four colours
- The number of bits for each pixel is the colour depth

Question 5

What is Metadata?

Answer 5

• Additional data stored with the image to define the width, height, colour depth/palette

Question 6

What is the effect on image size/quality when you change the colour depth/resolution?

Answer 6

• The greater the colour depth/res, the larger the file size
• The smaller the res, the lower the image quality
  (pixels are larger in low res, less needed to fill the space)

Question 7

How is sound sampled and stored in digital form?

Answer 7

• Analog sounds are converted to binary
• Sample rate - takes measures of sound waves at regular intervals
  eg. CD sampled at 44100Hz = 44100 samples taken per second
• Bit depth - affects the amount of info stored w each sample & helps the sound get as close to the original as possible

Question 8

How is the playback quality of a sound file affected by
a) Sample Rate
b) Bit Depth

Answer 8

a) More samples, more accurate sound
b) Larger depth, higher quality sound

Question 9

How is the size of a sound file affected by
a) Sample Rate
b) Duration
c) Bit Depth

Answer 9

a) The higher, the larger the file
b) Longer, larger file
c) The higher, the larger the file