Data Representation

Question 1

Why is Hexadecimal use? Give examples

Answer 1

• Hexadecimal is useful for representing large quantities of binary data as it only uses a few characters to represent lots of binary data.
• For example colour codes or in IP addresses.

Question 2

What is Hexadecimal known as?

Answer 2

Base 16

Question 3

What is a character set?

Answer 3

• A character set is a defined list of characters recognized by the computer.
• Each character is represented by a unique binary number.

Question 4

Give examples of characters sets?

Answer 4

• ASCII - a 7 but character set with 27 characters = 128
• Extended ASCII - an 8 bit character set with 28 characters = 256
• UNICODE - A 24 bit character set with 224 characters > 16 million

Question 5

Explain UNICODE

Answer 5

• UNICODE - A 24 bit character set with 224 characters > 16 million
• Unicode uses the same codes as ASCII up to 127.
  This means data encoded with Unicode will appear the same when using ASCII, assuming only the first 127 codes have been used.

Question 6

What is an analogue signal?

Answer 6

Analogue Signal: Natural sound waves, occurring in a continuous wave form, e.g.: human voice.

Question 7

What is a digital signal?

Answer 7

Digital signal: Discrete digital format for representing natural sound waves, e.g.: CDs and DVDs.

Question 8

What are Analogue-Digital Converters?

Answer 8

• An Analogue-Digital Converter is used to convert analogue sound into a digital format and vice versa.
• An example of an ADC is a Microphone
• An example of a DAC is a speaker

Question 9

What is Sampling Rate?

Answer 9

• Sampling rate: How often (frequency) you record the amplitude of a sound wave
• The more often you record a sample the smoother the playback will sound.

Question 10

What is Sample Resolution?

Answer 10

• Sample resolution: Represents how many different gradations of amplitude can be represented in a digital wave form.

Question 11

What is Nyquist Theorem?

Answer 11

• In 1928 Harry Nyquist worked out that if you wanted to produce an accurate recording you needed to use a sampling rate which is at least double that of the highest frequency in the original signal
• This theory was proven by Claude Shannon in 1949.

Question 12

What are the samples for the human ear and in audio CDs?

Answer 12

• In the human ear the sample is between 20Hz-20000Hz
• In Audio CDs, the sample is 44100 Hz

Question 13

What is MIDI?

Answer 13

• A MIDI is a technical standard.
• It describes
  
  1. A protocol
  2. Digital Interface
  3. Standard set of connectors
• This standard allows for a wide range of electronic musical instruments, computers etc, to communicate with each other.

Question 14

How does MIDI perform its function?

Answer 14

• It does this by using a MIDI controller to send and receive event messages to each device. The messages specify details such as:
  
  1. Duration of note
  2. Pitch
  3. Volume change
  4. Vibrato
  5. Temp synchronisation etc.

Question 15

What is MIDI essentially?

Answer 15

• MIDI is essentially a list of instructions on how to synthesis a sound. The sounds being pre-recorded digital samples of real instruments.
  The result is that a MIDI file uses far less disk space than a traditional digital recording (up to a 1000 times less.)

Question 16

What is the calculation for finding sound sample sizes?

Answer 16

• Size of Sample = (Number of samples per second) * (Number of bits per sample) * (Length of sample in seconds)

Question 17

What are Bitmaps?

Answer 17

Bitmaps use single discrete individual pixels of colour to make up an image

Question 18

What are Vectors?

Answer 18

Vectors use lists of information’s and mathematical equations to recreate an image based on the data.

Question 19

What is Colour Depth?

Answer 19

Colour Depth is the number of bits needed to store each pixel.
The greater the number of colours, the more bits required to store them.

Question 20

How do Vectors work?

Answer 20

• The properties of each geometric object/shape in the vector graphic image are stored as a list.
• The information on the object, e.g.: fill colour, length etc, are stored in a drawing list.

Question 21

What is an SVG?

Answer 21

• Scalable Vector graphics (SVG) is an XML - based image file format developed by the World Wide Web Consortium (WSC)
• All modern browsers have some support for rendering vector images in SVG format in browsers.

Question 22

What is the calculation for finding the storage requirements for bitmaps?

Answer 22

• Storage requirements = size in pixels * colour depth
• Divide by 8 to find the requirements in bytes

Question 23

What are the Pros of Vector Graphics?

Answer 23

Vector Graphics Pros:
* The file size is kept relatively small, regardless of how much
you scale the image.
* Will always scale without loss of quality.
* Can manipulate individual objects easily
* Great format for logos or images with simple shapes and
colours.

Question 24

What are the Cons of Vector Graphics?

Answer 24

Vector Graphics Cons:
* Cannot easily replicate an image with continuous areas of changing colour.
Individual pixels cannot be changed.

Question 25

What are the Pros of Bitmapped Graphics?

Answer 25

Bitmapped Graphics Pros:
* Great format for storing full colour images taken on a phone or
digital camera.
* Can manipulate individual pixels easily.
* Images/Photos can easily be altered, retouched etc.

Question 26

What are the Cons of Bitmapped Graphics?

Answer 26

Bitmapped Graphics Cons:
* Generally takes up more memory and file storage.
* Images don’t scale very well, they become pixelated the larger
they get.