Compression, Encryption and Hashing

Question 1

Define compression

Answer 1

A process used to reduce the storage space required by a file

Question 2

State 2 advantages of compression

Answer 2

• Can store more files with the same amount of storage space
• Allows quicker transfer of files over a network or the Internet
• Compressed files are quicker to download over the Internet
• Compressed files are quicker to search for

Question 3

State 2 purposes of compression

Answer 3

• Reducing the size of files
• Reducing download time
• Reducing storage requirements
• To make the best use of bandwidth

Question 4

Define lossy compression

Answer 4

A compression algorithm that removes non-essential date from a files leading to a noticeable decrease in the accuracy data

The data lost is unrecoverable

Question 5

Define lossless compressions

Answer 5

A compression algorithm that retains all the data in a file by only stating the instructions needed to reconstruct the original file

No data is lost

Question 6

State an advantage and disadvantage of lossless compression

Answer 6

Advs
- Can restore file in its original quality when uncompressed

• Ideal for vector- style images
• Ideal for text documents and executable programs

Disadvs
- typically less effective at reducing the file size

Question 7

Give two examples of lossless compression files

Answer 7

ZIP
PNG
GIF

Question 8

Why is lossless compression better suited for text documents and executable files?

Answer 8

For these files data must not be lost during compression because the file must be restored in its entirety, therefore lossless compression is more suitable

Question 9

Give two examples of lossy compression

Answer 9

JPEG
MP3
MPEG

Question 10

State an advantage and disadvantage of lossy compression

Answer 10

adv
- significantly reduces file size
- suitable for images, audio and videos

Disadvs
- Some data is lost when the file is compressed