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FILE SYSTEM• resides on secondary storage (disks) Provide efficient and convenient access to disk by allowing data to be : WRITECREATE OPEN CLOSE DELETE READ
STRUCTURE OF A FILE PHYSICAL FILE SYSTEM LOGICAL FILE SYSTEM FILE ORGANIZATION MODULE BASIC FILE SYSTEM I/0 CONTROL DEVICES
TYPES OF PHYSICAL FILE SYSTEM PILE DIRECT FILE SEQUENCIAL FILE INDEXED FILE
THE PILE• Datas are collected in the order they arrive.• Records may have different fields.• Record access is by exhaustible search.• Purpose is to accumulate the mass of data and save it. • Least complicated form of file organization
SEQUENCIAL FILE SYSTEM • Records are stored and retrieved serially one after the other. • The files are searched from its begging until the requested record is found.• If the record not matched on search then record not found is sent to the user.• File name and length are attributes of the file.
INDEXED FILE SYSTEM• Exhaustive index contain one entry for every record in the main file• Partial index contain entries to record where the field of interest exists• Records are accessed only through their indexes• Variable length record can be employed.