| 摘要 |
PURPOSE:To read out retrieval information from a document information file, even if the retrieval information is broken down, and to recover easily the retrieval information, by storing the retrieval information in advance not only in a retrieval information file but in the document information file. CONSTITUTION:In case retrieval information which is stored in a magnetic disk 10 is broken down, all the information is read from the head of an optical disk 8. Next, whenever a preamble is detected, retrieval information stored immediately after the preamble is reproduced, given to a buffer circuit 11 and stored in the magnetic disk 10. Also, on the optical disk 8, in case change retrieval information has existed immediately after the retrieval information, this change retrieval information is stored in the buffer circuit 11. A controlling circuit 14 replaces the retrieval information in which a registration number contained in the change retrieval information has coincided with a registration number in the retrieval information stored previously, in the magnetic disk, with the change retrieval information of the buffer circuit 11 and recovers it.
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