Range queries on Course + Year suggest an index on those fields.
Variable‑length records make pure direct access difficult without a pointer table.
High update frequency requires an organisation that handles inserts/deletes efficiently.
Recommended Solution
Organisation: Indexed Sequential File.
Data records stored sequentially in a main file (allows efficient bulk scans).
Primary index on StudentID for fast point lookups.
Secondary index on (Course, Year) to support range queries.
Access Method: Indexed access using the primary index for single‑record retrieval; secondary index for range queries.
Handling \cdot ariable Length: Store a fixed‑size pointer (byte offset) in the index entries; the main file can use a simple linked‑list of free spaces for deletions.
Justification
Fast \$O(\log n)\$ lookup via primary index meets the requirement for quick StudentID searches.
Secondary index enables \$O(\log n + k)\$ retrieval of \$k\$ records matching a Course/Year range.
Sequential storage of the data file keeps insert/delete overhead low compared with pure direct organisation.
Indexes occupy additional space but are justified by the performance gains for the expected query mix.
Suggested diagram: Block diagram showing the main data file, primary index (StudentID → byte offset), and secondary index (Course+Year → list of offsets).
Summary Checklist
Identify the dominant operations.
Determine record size characteristics.
Choose between sequential, indexed, direct, or hashed based on access patterns.
Consider hybrid solutions when multiple query types are required.
Validate the choice against storage limits and update frequency.