Ernest N Freeman

US Patent:

46726799, Jun 9, 1987

Filed:

Aug 16, 1983

Appl. No.:

6/523739

Inventors:

Ernest A. Freeman - Oakland CA

Assignee:

Wang Laboratories, Inc. - Lowell MA

International Classification:

G06K 972

US Classification:

382 40

Abstract:

A generalized method and apparatus for compression and decompression of textual information. Compression is performed by reading in succession each character and an associated context of a text, selecting for each character and associated context a corresponding code character, and providing the resulting code characters as the compressed form of the text. Decompression is a symmetric, inverse operation wherein the contexts associated with the code characters are read from a known decompressed portion of text. The context of a character is a group of text characters associated with a text character and containing a fixed number of characters. Text and code characters and contexts are related through a table containing a relative alphabet for the contexts of the language of the text. Each relative alphabet contains the text characters occurring in association with a corresponding context, and text characters within a given relative alphabet are identified by code characters assigned from set of code characters shared by the relative alphabets.