File Handling
Reading & Writing

OPEN · READ · WRITE · CLOSE · endOfFile()

CSZoneAQA GCSE Computer Science 8525

File Operations — AQA 8525

The Four File Commands

Command	Purpose	AQA Pseudocode
OPEN	Opens a file for reading or writing	OPEN 'data.txt'
READ	Reads a line from an open file	READ 'data.txt', line
WRITE	Writes a value to a file	WRITE 'data.txt', 'Hello'
CLOSE	Closes the file when done	CLOSE 'data.txt'

Always CLOSE files:Not closing a file can cause data loss or corruption.

Reading from a File

OPEN 'scores.txt'
WHILE NOT endOfFile('scores.txt')
READ 'scores.txt', line
OUTPUT line
ENDWHILE
CLOSE 'scores.txt'

endOfFile('filename') returns True when there are no more lines left to read. Use it with WHILE NOT to process every line.

Writing to a File

WRITE (creates/overwrites)

OPEN 'results.txt'
WRITE 'results.txt', 'Ali: 85'
WRITE 'results.txt', 'Beth: 72'
CLOSE 'results.txt'

WRITING IN A LOOP

names ← ['Ali','Beth','Carlos']
OPEN 'out.txt'
FOR i ← 0 TO 2
WRITE 'out.txt', names[i]
ENDFOR
CLOSE 'out.txt'

Exam Practice

AQA-style question

Write pseudocode to open a file called 'names.txt' and read all lines from it, outputting each one. Then close the file.

4 marks

OPEN 'names.txt'
WHILE NOT endOfFile('names.txt')
READ 'names.txt', name
OUTPUT name
ENDWHILE
CLOSE 'names.txt'

Key Takeaways

File operations: OPEN → READ/WRITE → CLOSE

endOfFile('file') — returns True when no more data to read

WHILE NOT endOfFile() — standard pattern to read all lines

Always CLOSE the file — prevents data loss