This unit dealt along with the methods of physically storing data in the files. The terms fields, records & files were described. The organization types were introduced.
The several file organization techniques were discussed. Sequential File Organization finds employ in application areas where batch processing is more common. Sequential files are simple to employ and can be stored on cheap media. They are appropriate for applications that need direct access to only specific records of the collection. They do not provide sufficient support for interactive applications.
In Direct file organization, there exists a predictable relationship among the key used and to identify a specific record on secondary storage. A direct file has to be stored on a direct access device. Direct files are utilized extensively in application areas where interactive processing is utilized.
An Indexed Sequential file supports both sequential access through key value & direct access to a specific record, given its key value. It is implemented by developing an index on top of a sequential data file that resides on a direct access storage device.