PURPOSE: To improve the efficiency of a dictionary, and also, to improve the data compressibility.
CONSTITUTION: A data compressing means 11 encodes a character-string of input data by designating it by a number of that of the longest coincidence from in the character strings registered in a dictionary, and registers a partial character-string which is each different partial character-string beginning with each character in encoded character string data, and obtained by lengthening the character-string subjected to longest coincidence in those which are already registered in the dictionary by one character, in the dictionary by giving newly a number thereto. A data restoring means 15 decodes the data by retrieving the dictionary by the number based on compressed data to be restored, and registers a partial character string which is each different partial character string beginning with each character in decoded character-string data, and obtained by lengthening the character string subjected to longest coincidence in those which are registered in the dictionary already by one character, in the dictionary by giving newly a number thereto.
OKADA YOSHIYUKI
NAKANO YASUHIKO
CHIBA HIROTAKA
