Files

A file is a named collection of related data stored on secondary storage (e.g., hard drive, SSD). In programming, files are used to store data persistently — data that survives when the program ends.

• Text files (.txt, .csv): store data as plain text
• Binary files: store data in binary format (images, audio, executables)

File Operations in pseudocode:

• OPEN("file.txt", "r") — open for reading
• OPEN("file.txt", "w") — open for writing (overwrites)
• OPEN("file.txt", "a") — open for appending
• READ(fileHandle, data) — read from file
• WRITE(fileHandle, data) — write to file
• CLOSE(fileHandle) — close file
• EOF(fileHandle) — check if at end of file

Databases

A database is an organised collection of structured data, typically stored in tables. A relational database uses multiple tables linked by relationships.

• Table: stores records in rows and columns
• Primary key: a unique field that identifies each record
• Foreign key: a field in one table that refers to the primary key in another table

Example — School Database

SQL Queries

SQL (Structured Query Language) is used to query and manipulate relational databases:

• SELECT name, grade FROM Students WHERE grade > 70;
• SELECT * FROM Students ORDER BY name;
• INSERT INTO Students VALUES (101, 'Aisha', 85);
• UPDATE Students SET grade = 90 WHERE studentID = 101;
• DELETE FROM Students WHERE studentID = 101;

Files vs Databases