2.4b File handling — Edexcel 4CP0

Why File Handling?

Data stored in variables is lost when a program ends — it only exists in RAM. To persist data between runs, programs must read from and write to files stored on secondary storage (e.g. hard drive, SSD).

File Operations

Edexcel 4CP0 requires knowledge of four file operations:

Operation	Purpose	Pseudocode keyword
Open	Opens a file for reading or writing	OPEN
Read	Reads data from an open file into a variable	RECEIVE … FROM FILE
Write	Writes data to an open file (overwrites existing content)	SEND … TO FILE
Close	Closes the file once operations are complete	CLOSE

Reading from a File

OPEN "scores.txt"
RECEIVE score FROM FILE
SEND "Score read: " & score TO DISPLAY
CLOSE "scores.txt"

Writing to a File

OPEN "scores.txt"
SET score TO 85
SEND score TO FILE
CLOSE "scores.txt"

Appending to a File

Appending adds new data to the end of an existing file without deleting what is already there. This is different from writing, which overwrites the file contents.

# Append a new score without losing old data
OPEN "scores.txt" APPEND
SET newScore TO 92
SEND newScore TO FILE
CLOSE "scores.txt"

Reading an Entire File

OPEN "names.txt"
WHILE NOT end of file DO
    RECEIVE name FROM FILE
    SEND name TO DISPLAY
END WHILE
CLOSE "names.txt"

File Handling Summary

Mode	Effect on existing data	Use when…
Write	Overwrites — old data is lost	You want to create a fresh file or replace content
Append	Adds to the end — old data preserved	You want to add new records without losing existing ones
Read	Does not change the file	You only need to retrieve data

📝 Exam Tip: Always CLOSE a file after using it. Failing to close can result in data not being saved correctly. Many exam questions ask you to identify what is missing — it's often the CLOSE statement.

⚠️ Common Mistakes

Forgetting to close the file — data may not be written to secondary storage
Confusing write and append — writing overwrites all existing data
Trying to read a file that hasn't been opened first — always OPEN before RECEIVE