Compression

Compression ( or compaction) is the encoding of data to save storage space or transmission time. Although data is already coded in digital form for computer processing, it can often be coded more efficiently (using fewer bits). For example, replaces strings of repeated characters (or other units of data) with a single character and a count. There are many compression algorithms and utilities. Compressed data must be decompressed before it can be used.

The standard Unix compression utilty is called though 's superior  has largely replaced it. Other compression utilties include, zip and.

When compressing several similar files, it is usually better to join the files together into an of some kind (using  for example) and then compress them, rather than to join together individually compressed files. This is because some common compression s build up tables based on the data from their current input which they have already compressed. They then use this table to compress subsequent data more efficiently.