Compression

Compression is a reduction in the number of bits needed to represent data.

Compressing data can save storage capacity, speed file transfer, and decrease costs for storage hardware and network bandwidth.

Lossless compression

Lossless compression enables the restoration of a file to its original state, without the loss of a single bit of data, when the file is uncompressed.

Lossless compression is the typical approach with executable, as well as text and spreadsheet files, where the loss of words or numbers would change the information.

 Lossy compression

Lossy compression permanently eliminates bits of data that are redundant, unimportant or imperceptible.

Lossy compression is useful with graphics, audio, video and images, where the removal of some data bits has little or no discernible effect on the representation of the content.

ADVANTAGES OF DATA COMPRESSION

• Less disk space (more data in reality)
• Faster writing and reading
• Faster file transfer
• Variable dynamic range
• Byte order independent

DISADVANTAGES OF DATA COMPRESSION 

• Added complication
• Effect of errors in transmission
• Slower for sophisticated methods (but simple methods can be faster for writing to disk.)
• "Unknown" byte / pixel relationship