| 摘要 |
PURPOSE: To effectively use a memory and to provide useful service by erasing unnecessary data when erasing time is passed and preserving useful data for a long time. CONSTITUTION: The file control information on the mail box of a minimum number is read from the mail box control area of a first RAM 3. Erasing time is read from the block parameter, the present time is read from a RTC 11 and they are compared. When the erasing time is already passed, an access counter is read from the block parameter, the number of times of access reference is read from a system parameter and they are compared. When an access counter is large, extension time is added to the read erasing time, the erasing time is updated and, at the same time, the access counter is initialized. Subsequently, when an extension counter is matched with an extension reference, image information is erased and the file control information corresponding to it is updated. As a result, useful data having many number of times of access can be preserved and data having a few number of times of access is erased after the erasing time. |
