Compression

Created by

Evelyn Clarke

Cards (9)

Data compression is when we make file sizes smaller, while trying trying to make the compressed file as true to the original as possible.
Compressing data files has many uses:
Smaller files take up less storage space on a device
Streaming and downloading files from the Internet is quicker as they take up less bandwidth
It allows webpages to load more quickly in web browsers
Email services normally have restrictions on the size of an attachment you can send- compressing the file allows you to send the same content with a much smaller file size
Lossy compression
Works by permanently removing data from the file- this limits the number of bits the file needs and so reduces its size.
Lossless compression
Works by making the file smaller by temporarily removing data to store the file and then restores it to its original state when it's opened.
What are the two types of compression?
Lossy
Lossless
What are the advantages of lossless compression?
Data is only removed temporarily so there is no reduction in quality- the compressed file should look or sound like the original
Lossless files can be decompressed- turned back into the original
Lossless compression can be used on text and software files
What are the advantages of lossy compression?
Greatly reduced file size, meaning more files can be stored
Lossy files take up less bandwidth so can be downloaded and streamed more quickly
Commonly used- lots of software can read lossy files
What are the disadvantages of lossy compression?
Lossy compression loses data- the file can't be turned back into the original
Lossy compression can't be used on text or software files as these files need to retain all the information of the original
Lossy files are worse quality than the original (but this loss in quality is normally unnoticeable)
What are the disadvantages of lossless compression?
Only a slight reduction in file size, so lossless files still take up quite a bit of space on your device