File Modes: READ, WRITE and APPEND — 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.

A file must be opened in a mode that tells the operating system what the program intends to do with it. The mode appears after FOR in the OPENFILE statement. CIE pseudocode has three file modes: READ, WRITE and .

Mode	What it does	What happens to existing contents
`READ`	Opens the file for reading only	Untouched; the file must already exist
`WRITE`	Opens the file for writing new content	Erased: if the file already exists, its contents are overwritten
`APPEND`

READ

Used when the program needs to load data from a . The file must already exist; opening a non-existent file in READ mode causes an error.

OPENFILE "students.txt" FOR READ
READFILE "students.txt", Name
OUTPUT Name
CLOSEFILE "students.txt"

WRITE

Used when the program is creating a new file or completely replacing an existing one. If the file already exists, everything in it is wiped out before the new content is written.

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

Important: opening a file that already has data in WRITE mode destroys its existing contents before writing. To keep the existing data and add to it, use APPEND mode instead.

APPEND

Used when the program needs to add new content to the end of a file without erasing what is already there. If the file does not yet exist, it is created.

OPENFILE "log.txt" FOR APPEND
WRITEFILE "log.txt", "New entry added at the end"
CLOSEFILE "log.txt"

Choosing the right mode

Goal	Use mode
Load existing data into the program	READ
Create a fresh new file (or replace an old one entirely)	WRITE
Add a new record to the end of an existing file	APPEND