| 摘要 |
PURPOSE:To decrease the reduction of compressibility generated due to the change of a shift group by allowing original codes having high appearance probability in an original code string of the shift group to belong to all of the plural shift groups. CONSTITUTION:In the correspondence of the original codes, shift codes and discrimination codes, spaces belong to both shift groups, a shift code F and a shift code O. At the convertion of an original code belonging to plural shift groups into a compression code, one original code corresponds to plural compression codes. At the sequential conversion of each original code, the original code is once translated into plural compression codes corresponding to plural shift groups. Since a shift group of which a compression code completed at its conversion immediately before belongs is stored until the convertion of the succeeding original code, the compression code is selected from the immediately preceding shift group. At the conversion into the original code, said selecction is unnecessary.
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