Writing to a File — File Handling | IGCSE Computer Science

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 3% of your exam marks.

stable

Rare

Stable3%

OPENFILE, READFILE, WRITEFILE, CLOSEFILE pseudocode operations appear occasionally.

Writing uses the WRITEFILE keyword once the file has been opened FOR WRITE.

Writing a new file (WRITE mode)

Used when starting fresh, or when overwriting an existing file:

OPENFILE "report.txt" FOR WRITE
WRITEFILE "report.txt", "Sales Report 2024"
WRITEFILE "report.txt", "Total: £125,000"
WRITEFILE "report.txt", "Customers: 1,432"
CLOSEFILE "report.txt"

After this runs, report.txt contains exactly those three lines. Any previous content is gone, because opening in WRITE mode overwrites the file.

Adding to existing data

To add new lines without losing the existing ones, open the file FOR APPEND. New data is written after the existing content, leaving what is already in the file untouched.

OPENFILE "log.txt" FOR APPEND
WRITEFILE "log.txt", NewLine
CLOSEFILE "log.txt"

Exam tip

Writing to a file in pseudocode

What comes up: write pseudocode to open a file, store a value to it, and close it (a 3-mark question).

Write (three marks): (1) Open the file in WRITE mode — OPENFILE "filename.txt" FOR WRITE. (2) Write the variable to the file — WRITEFILE "filename.txt", VariableName. (3) Close the file — CLOSEFILE "filename.txt". Each of these three lines is a separate mark point.

Watch out: CLOSEFILE is its own credited mark — the mark scheme awards it independently, so dropping it loses a mark even though the data appears written. Also, opening in WRITE mode silently destroys any existing file contents; if the question needs the existing data kept, read it in first and write it back out along with the new data.