Indexed Sequential Organization [Data Structures]

This is a filing method used on direct access storage devices in which records are arranged in logical sequence by a key. Indexes to these keys permit direct access to individual records. In this file organization, the records of the file are stored one after another in the order they are added to the file. Indexed files can have random or sequential access modes. There is a range of keys (k1 to kn) that belong to a block. From key -> Block no. -> (sector no, Track no). The records need not to be sorted.