DATA CORRECTING SYSTEM ON UNREWRITABLE MEDIUM

PURPOSE:To control rewritably by adding a correcting block to an unwritten area and recording a writing position. CONSTITUTION:An input/output request program 2 successively requests an input output control means 4 to input the data record in a data file 1. The means 4 obtains a block position to be inputted from the file 1 while it inputs a block position data from an index file 3 to an index buffer 6. In accordance with this, the data are inputted to a data buffer 5 and a data record requested from the inside of the block is delivered to a program 2. At the time of the necessity, the inputted data record is corrected, delivered to the means 4 and requested to be replaced to an original record. The means 4 replaces the original record in the buffer 5 to the record after the correction, outputs newly the block to the unwritten area in the file 1, changes the position data of the corresponding block in the buffer 6 to he new data and outputs them to the index file 3. Thus, by recording the writing position, the re-writing can be executed.