Show understanding of why files are needed

10.3 Files – Why Files Are Needed

In computer systems, a file is a named collection of related data stored on secondary storage. Files provide a mechanism for preserving information beyond the lifetime of a program’s execution and for organising data in a way that can be accessed by multiple programs or users.

Key Reasons for Using Files

• Persistence: Data remains available after the program terminates, unlike variables that exist only in RAM.
• Large Data \cdot olumes: Files can hold far more data than can be kept in main memory at one time.
• Data Sharing: Multiple programs or users can read from and write to the same file, enabling collaboration.
• Organization and Structure: Files can be grouped into directories, allowing logical categorisation of related information.
• Backup and Recovery: Files can be copied, archived, or restored, protecting against data loss.
• Interoperability: Standard file formats allow data exchange between different hardware, operating systems, and applications.

Comparison: Variables vs. Files

Illustrative Example

Consider a student‑record system that must retain information about each pupil for several years. The program can:

1. Read a file students.txt at start‑up to load existing records into memory.
2. Allow the user to add, modify, or delete records during the session.
3. Write the updated data back to students.txt before exiting, ensuring the changes are saved for future sessions.

This workflow demonstrates persistence, data sharing (multiple users can open the same file), and the ability to handle a data set that may exceed the available RAM.

Mathematical Perspective

If a program processes \$n\$ data items, each of size \$s\$ bytes, the total memory required is \$M = n \times s\$. When \$M\$ exceeds the available RAM \$R\$, the program must use external storage:

\$\$

\text{If } n \times s > R \;\Longrightarrow\; \text{store data in a file.}

\$\$

Summary

• Files provide permanent storage, enabling data to outlive program execution.
• They support handling of large data sets, data sharing, and systematic organization.
• Understanding why files are needed underpins later topics such as file I/O operations, file formats, and data security.