data compression

In computing, techniques for reducing the amount of storage needed for a given amount of data. They include word tokenization (in which frequently used words are stored as shorter codes), variable bit lengths (in which common characters are represented by fewer bits than less common ones), and run-length encoding (in which a repeated value is stored once along with a count).

In lossless compression the original file is retrieved unchanged after decompression. Some types of data (sound and pictures) can be stored by lossy compression where some detail is lost during compression, but the loss is not noticeable. Lossy compression allows a greater level of compression. The most popular compression program is PKZIP, widely available as shareware.

Compressed files take up less storage space and can be transmitted across the Internet much faster. Most modems include facilities for compressing data while in transmission. New standards of compression have been developed for audio and video, such as DVI (digital video interactive) and MPEG.