Method of managing storage medium

Claim 1

A computer data management system for a write-once type storage medium, which includes a plurality of sectors, for recording data including at least file data and file management information, wherein the recording of the data on the write-once type storage medium, including the at least file data and file management information, is performed by recording new file data on the write-once type storage, by updating a current file management information stored on a rewritable type memory, wherein said updated current file management information comprises a pointer to at least one address of the recorded new file data, and by recording a difference-information on the write-once type storage medium, wherein the difference-information comprises information which corresponds to the difference between the current file management information and the updated current file management information, said system comprising: a) difference-information recording means for recording difference-information on at least a number of sectors of said plurality of sectors of said write-once type storage medium; b) difference-information gathering means for reading said number of sectors of said plurality of sectors of said storage medium and extracting said difference information recorded in at least some of said number of sectors, upon each recording of a new item of said file data on said write-once type storage medium, and for gathering and recording in one sector of said plurality of sectors of said write-once type recording medium said difference-information so extracted from said number of sectors of said plurality of sectors, wherein a record size of a sum of said difference information so extracted is smaller than a size of said one sector of said plurality of sectors; and c) converter/loader means for reconstructing said current file management information stored on said rewritable type memory by reading and storing in said rewritable type memory all of said difference information included in said one sector of said plurality of sectors and included in any ones of said number of sectors including said difference information that were recorded by said difference information recording means but were not gathered or recorded by said difference-information gathering means, at least at a time when said computer system is powered on or a time when said write-once type storage medium is to be ejected and exchanged for another write-once-type storage medium.