| 摘要 |
PROBLEM TO BE SOLVED: To disable the use of a disk by inhibiting the read-in of data of the copied disk. SOLUTION: By using a CD-ROM drive 4 mounted with a 2nd pickup 3 reading in an identification code recorded on the label surface 12 of the disk 1, the existence of the identification code recorded on the label surface 12 of the disk 1 is discriminated. By this procedure, the discrimination is made whether the disk 1 is the master or copied one, then the use of the disk 1 is disabled by prohibiting the read-in of the data of the copied disk 1.
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