8.4 File Handling — Cambridge IGCSE CS 0478

Why File Handling?

Variables and arrays store data temporarily in RAM — when a program ends, that data is lost. File handling allows data to be saved permanently to secondary storage (e.g., a hard drive) so it can be retrieved later by the same or another program.

File Operations in Cambridge Pseudocode

Operation	Keyword	Purpose
Open for reading	`OPENFILE "name" FOR READ`	Open an existing file to read from it
Open for writing	`OPENFILE "name" FOR WRITE`	Open/create file to write data (overwrites)
Open for append	`OPENFILE "name" FOR APPEND`	Open existing file to add data at the end
Read a line	`READFILE "name", variable`	Read the next line from the file into variable
Write a line	`WRITEFILE "name", data`	Write data to the file
Close a file	`CLOSEFILE "name"`	Close file when done (important!)
End of file check	`EOF("name")`	Returns TRUE when no more data to read

Writing to a File

OPENFILE "scores.txt" FOR WRITE
WRITEFILE "scores.txt", "Alice,95"
WRITEFILE "scores.txt", "Bob,82"
WRITEFILE "scores.txt", "Carol,78"
CLOSEFILE "scores.txt"

Reading from a File

OPENFILE "scores.txt" FOR READ
READFILE "scores.txt", line
OUTPUT line             // Outputs: Alice,95
CLOSEFILE "scores.txt"

Reading All Lines (until EOF)

OPENFILE "scores.txt" FOR READ
WHILE NOT EOF("scores.txt") DO
    READFILE "scores.txt", line
    OUTPUT line
ENDWHILE
CLOSEFILE "scores.txt"

Appending to a File

OPENFILE "scores.txt" FOR APPEND
WRITEFILE "scores.txt", "David,91"
CLOSEFILE "scores.txt"
// David's score is added at the end; previous data preserved

Writing vs Appending

Mode	Effect on existing data	Use case
FOR WRITE	Overwrites — all old data lost	Creating new file or replacing all data
FOR APPEND	Preserves old data, adds new data at end	Adding new records without deleting old ones

Exam tip: Always show OPENFILE and CLOSEFILE in your answers — marks are awarded for these. Use WHILE NOT EOF() DO to read all records in a file. In exams, the file name is given as a string in quotes. Remember: FOR WRITE overwrites; FOR APPEND adds to end.

⚠️ Common Mistakes

Forgetting CLOSEFILE — always close the file when done
Using FOR READ when you want to write, or FOR WRITE when reading
Using FOR WRITE when you only want to add records — use FOR APPEND to preserve existing data
Forgetting NOT in WHILE NOT EOF() — without NOT, the loop runs while the file IS at end (immediately exits)

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Worksheet — File Handling

4 questions · 11 marks

Q1Write pseudocode to open a file "names.txt" for writing, write three names to it, then close it. [3]

✅ Mark scheme

OPENFILE "names.txt" FOR WRITE [1]; WRITEFILE "names.txt", "Alice"; WRITEFILE "names.txt", "Bob"; WRITEFILE "names.txt", "Carol" [1]; CLOSEFILE "names.txt" [1]

Q2Write pseudocode to read and output all lines from "data.txt" until the end of the file is reached. [4]

✅ Mark scheme

OPENFILE "data.txt" FOR READ [1]; WHILE NOT EOF("data.txt") DO [1]; READFILE "data.txt", line [1]; OUTPUT line [1]; ENDWHILE; CLOSEFILE "data.txt"

Q3Explain the difference between opening a file FOR WRITE and FOR APPEND. [2]

✅ Mark scheme

FOR WRITE creates/overwrites the file — all existing data is lost [1]; FOR APPEND adds new data to the end of the file while preserving all existing records [1]

Q4Why is it important to close a file after use? [2]

✅ Mark scheme

Any two: Closing ensures all data is actually saved/flushed to disk [1]; Releases the file so other programs can access it [1]; Prevents data corruption [1]; Frees system resources [1]

Quiz — File Handling

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Why File Handling?

File Operations in Cambridge Pseudocode

Writing to a File

Reading from a File

Reading All Lines (until EOF)

Appending to a File

Writing vs Appending

Worksheet — File Handling

Mini Test — File Handling