Learn about data compression

1. Computer Science
CIE-Syllabus 2210
Lesson 20
Principles of data
compression
Tutor: Suraj Motee

2. Learning Outcomes
• Differentiate between lossless and lossy compression.

3. What is compression?
• Compression is the process of encoding information using
fewer bits so that the compressed file size is smaller.

4. What is compression?
Original
A bits
Compression Process Compressed
B bits
B < A

5. Types of compression
Lossless Lossy

6. True or False
• Compression produces a larger file size.
• Compression works by reducing the number of bits.
• Compression does not produce a second file but modify the
original one.
FALSE
TRUE
FALSE

7. LOSSLESS COMPRESSION
Original
100 MB
Compressed
50 MB
Restored
100 MB
LOSSLESS COMPRESSION can reduce file size without losing quality.

8. LOSSY COMPRESSION
Original
100 MB
Compressed
50 MB
Restored
80 MB
LOSSY COMPRESSION removes unnecessary information and redundant data so as to reduce the size of
the file.

9. LOSSLESS OR LOSSY
• Compressed file cannot be restored to the same original file.
• Quality is affected.
• Compression technique that produce a second file that can
be restored back to original file size.
LOSSY
LOSSY
LOSSLESS