digital data compression

Question 1

what is text?

Answer 1

encoded using ASCII or Unicode to assign binary codes to characters

Question 2

what is images?

Answer 2

encoded by assigning codes to the colour of each pixel

Question 3

what is sound?

Answer 3

encoded by sampling analogue waves and assigning binary values to each sample

Question 4

what are some types of compression

Answer 4

Lossless – file size reduced with no data lost
◎ Size reduction is limited
◎ File can be fully recovered on decompression Lossy – file size reduced with some data loss
◎ More reduction of file size
◎ Recovered file may be of reduced quality

Question 5

what is huffman coding

Answer 5

• The number of times data occurs is checked
• The data is sorted in a binary tree so that:
• The data with the highest frequency has the
  shorter codes – top of the tree
• The data with the lowest frequency has longer
  codes – bottom of the tree

Question 6

what is a huffman tree?

Answer 6

• Binary tree: root at the top, grows downwards
• Every point is a node, every line is a branch
• Every node can have a maximum of two branches