FILE CONTROL SYSTEM

PURPOSE:To attain a control system for used/unused region which is suited to an unrewritable file medium, etc. by dividing a file into plural regions and putting identification marks corresponding to each partial region on the file medium. CONSTITUTION:The values of EOP1 and EOP2 (end address of partition) are stored in identification marks (usage marks) UM1 and UM2 showing the addresses of used partial regions respectively. An index part is written every time the data is registered to the data set (m). The end address of partition is written to the corresponding UM on a label region at a time point when a partition of the index part is fully used. The retrieval is performed to the used/unused regions of the data set by referring to the UM of the label region as well as the index part of the data set.