Give reasons to compress data

Describe how compression affects file size

Identify disadvantages of compressing files

Explain difference between lossless and lossy compression

Describe advantages of lossless and lossy compression

Making a file's storage size smaller

Making a file unreadable

Making a second coopy of a file

Making a machine code version of a source file

Files

Folders

Programs

Data

size

smaller

type

executable

size

larger

contents

unreadable

To reduce storage requirements

To reduce network transmission time

To reduce execution time

To reduce translation time

lossless

lossy

lossable

lossmore

.jpg

.png

.bmp

.gif

.jpg

.png

.bmp

No data is removed

Original data can be reconstructed

Achieves higher level of compression

Can be applied to all types of data

Data is encoded rather than removed

Original data can be reconstructed

Achieves higher level of compression

Data loss usually not noticeable to human perception

Parts of the original data is removed forever

Original data can not be reconstructed (decompressed)

Achieves lower level of compression

Data loss usually vnoticeable to human perception

Parts of the original data is removed forever

Original data can not be reconstructed (decompressed)

Achieves lower levels of compression

Data loss usually very noticeable to human perception

size

algorithm

type

method

format

ratio

Describe how compression affects file size

Give reasons for reducing file sizes

Explain difference between lossless and lossy compression

Explain advantages/disadvantages of both

Identify problems with compression