Patent ID: 6917570

Claim:
A medium controller storing a plurality of media therein, having a medium transfer unit to take a medium in and out of a storage place to read or write information on the medium and to transfer the medium to a place where reading and writing information is possible, and managing information about media in storage, comprising: slots for storing media; sensors, each mounted in each of the slots, for detecting whether or not there is a medium in said slot; a sensor manager for holding a log of status of said sensors in a period when media are likely to be taken in or out manually and deciding changes in the status of said sensors; and a medium information reader for reading medium information, which identifies a medium, from the medium, wherein when it is decided from a decision result by said sensor manager that the medium has been replaced, medium information is read by said medium information reader to thereby update medium storage information, or when it is decided that the medium has not been replaced, said medium storage information is not updated.