File formats
and compression

File formats

Here are the main file formats you need to know:

Standard	Definition	Uses
JPG or JPEG	Joint Photographic Experts Group	Stores images with lossy compression.
GIF	Graphic Interchange Format	Stores bitmapped images using lossless compression.
PDF	Portable Document Format	Shows documents the same way with any software that opens them.
MP3	Moving Picture Experts Group Audio Layer III	Digital audio using lossy compression.
MPEG	Moving Picture Experts Group	Represents videos using lossy compression.

Compression

Compression is used to reduce the size of files. This is done to save storage space on portable devices and to reduce transmission and download times on networks like the internet. The disadvantage of compression is that they need to be decompressed which slows operation times.

There are 2 main types of compression:

• Lossy compression: Reduces file size and quality by removing data that won’t be noticed. For example, in images unnoticed colours and details are removed. In music, unnoticed sounds are removed. This reduces the quality. When the data is uncompressed it is not exactly the same as the original but the difference is so small that it cannot normally be noticed.
• Lossless compression: Original file keeps the same quality but the size is reduced by noticing patterns and compressing them. E.g. include compressed text files.