com·pres·sion   (kəm-prěsh'ən)    n.   The act or process of compressing. The state of being compressed. The process by which the working substance in a heat engine, such as the vapor mixture in the cylinder of an internal-combustion engine, is compressed. The engine cycle during which this process occurs. The process by which the working substance in a heat engine, such as the vapor mixture in the cylinder of an internal-combustion engine, is compressed. The engine cycle during which this process occurs. Computer Science The process by which data is compressed into a form that minimizes the space required to store or transmit it. com·pres'sion·al adj.

Compression

Com*pres"sion\, n. [L. compressio: cf. F. compression.] The act of compressing, or state of being compressed. "Compression of thought." --Johnson.

compression

See data compression.

Main Entry: com·pres·sion
Pronunciation: k&m-'presh-&n
Function: noun
: the act, process, or result of compressing especially wheninvolving a compressing force on a bodily part <compression of an artery by forceps> <compression of the brain by the bones of a depressed fracture>

compression com·pres·sion (kəm-prěsh'ən)
n.

1. See condensation.
2. The state of being compressed.

compression   (kəm-prěsh'ən)  Pronunciation Key  A force that tends to shorten or squeeze something, decreasing its volume. The degree to which a substance has decreased in size (in volume, length, or some other dimension) after being or while being subject to stress. See also strain. The re-encoding of data (usually the binary data used by computers) into a form that uses fewer bits of information than the original data. Compression is often used to speed the transmission of data such as text or visual images, or to minimize the memory resources needed to store such data.

compression
1. (Or "compaction") The coding 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, run-length encoding 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 compress though GNU's superior gzip has largely replaced it. Other compression utilties include pack, zip and PKZIP.
When compressing several similar files, it is usually better to join the files together into an archive of some kind (using tar for example) and then compress them, rather than to join together individually compressed files. This is because some common compression algorithms 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.
See also TIFF, JPEG, MPEG, Lempel-Ziv Welch, "lossy", "lossless".
Compression FAQ.
Web Content Compression FAQ.
Usenet newsgroups: comp.compression, comp.compression.research.
2. Reducing the dynamic range of an audio signal, making quiet sounds louder and loud sounds quieter. Thus, when discussing digital audio, the preferred term for reducing the total amount of data is "compaction". Some advocate this term in all contexts.
(2004-04-26)