A semiconductor disk wherein a flash memory into which data is rewritten in block unit is employed as a storage medium, said semiconductor disk comprises a data memory in which file data are stored, a substitutive memory which substitutes for blocks of errors in the data memory, an error memory in which...http://www.google.com/patents/US5644539?utm_source=gb-gplus-sharePatent US5644539 - Storage device employing a flash memory
