Explain sequential file organization. Differentiate between sequential file and index sequential file. Explain the advantages of indexed sequential file over sequential file with suitable examples.

Sequential File Organization:

Sequential file organization is a basic file organization technique in which records are stored in a file in the order in which they are created or entered. Each record occupies a fixed amount of space, and records are accessed sequentially, one after the other.

Characteristics of Sequential File Organization:

• Records are stored in contiguous memory locations.
• Each record has a unique key field that is used to identify the record.
• Records are accessed sequentially, one after the other.
• Insertion and deletion of records are inefficient as it requires shifting of records to maintain the sequential order.

Index Sequential File Organization:

Index sequential file organization is a variation of sequential file organization that uses an index to improve the efficiency of data access. The index contains a list of key values and their corresponding record locations in the file.

Characteristics of Index Sequential File Organization:

• Records are stored in contiguous memory locations.
• Each record has a unique key field that is used to identify the record.
• An index is maintained that contains a list of key values and their corresponding record locations in the file.
• Records can be accessed sequentially or directly using the index.
• Insertion and deletion of records are more efficient than in sequential file organization, as the index can be used to locate the record's location in the file.

Advantages of Indexed Sequential File Organization over Sequential File Organization:

• Faster data access: Index sequential files allow direct access to records using the index, which is much faster than sequential access.
• More efficient insertion and deletion: Insertion and deletion of records are more efficient in index sequential files because the index can be used to locate the record's location in the file.
• Better space utilization: Index sequential files can make better use of disk space by storing records in contiguous memory locations.
• More flexibility: Index sequential files offer more flexibility in terms of data access and organization.

Examples of Sequential and Index Sequential File Organization:

• Sequential file organization: A company's customer database, where customer records are stored in the order in which they were created.
• Index sequential file organization: A library's book catalog, where book records are stored in the order of their accession numbers and an index is maintained to allow direct access to books by title or author.