File Handling: Reading from and Writing to Text Files

This lesson covers file handling as required by OCR J277 Section 2.3. File handling allows programs to read data from files and write data to files, so that information persists even after the program has finished running. OCR uses specific pseudocode syntax for file operations that you must know for the exam.

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Why Use File Handling?

When a program ends, all data stored in variables is lost. File handling allows programs to:

• Save data permanently (e.g. high scores, user settings, logs)
• Read data that was previously saved
• Process large amounts of data stored in files
• Share data between different programs

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OCR File Handling Pseudocode

OCR uses specific functions for file handling:

Function	Purpose
openRead(filename)	Opens a file for reading
openWrite(filename)	Opens a file for writing (creates new or overwrites)
readLine()	Reads the next line from the file
writeLine(data)	Writes a line of data to the file
close()	Closes the file
endOfFile()	Returns true if the end of the file has been reached

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Reading from a File

OCR Pseudocode:

myFile = openRead("students.txt")

while NOT myFile.endOfFile()
    line = myFile.readLine()
    print(line)
endwhile

myFile.close()

Python:

# Method 1: Using with statement (recommended)
with open("students.txt", "r") as my_file:
    for line in my_file:
        print(line.strip())  # strip() removes the newline character

# Method 2: Reading all lines into a list
with open("students.txt", "r") as my_file:
    lines = my_file.readlines()
    for line in lines:
        print(line.strip())

Reading Line by Line

myFile = openRead("data.txt")
firstLine = myFile.readLine()
secondLine = myFile.readLine()
print(firstLine)
print(secondLine)
myFile.close()

with open("data.txt", "r") as my_file:
    first_line = my_file.readline().strip()
    second_line = my_file.readline().strip()
    print(first_line)
    print(second_line)

OCR Exam Tip: Always remember to close() the file after reading or writing in OCR pseudocode. In Python, using the with statement automatically closes the file, which is considered best practice. In the exam, if writing pseudocode, you MUST include close().

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Writing to a File

OCR Pseudocode:

myFile = openWrite("output.txt")
myFile.writeLine("Hello, World!")
myFile.writeLine("This is line 2")
myFile.writeLine("This is line 3")
myFile.close()

Python:

with open("output.txt", "w") as my_file:
    my_file.write("Hello, World!\n")
    my_file.write("This is line 2\n")
    my_file.write("This is line 3\n")

Important: openWrite Overwrites!

When you use openWrite(), if the file already exists, its contents are completely replaced. This is important to remember — you could accidentally lose data.

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Practical Example: Saving and Loading High Scores

Saving Scores

OCR Pseudocode:

names = ["Alice", "Bob", "Charlie"]
scores = [150, 120, 180]

myFile = openWrite("highscores.txt")
for i = 0 to 2
    myFile.writeLine(names[i] + "," + str(scores[i]))
next i
myFile.close()
print("Scores saved!")

Python:

names = ["Alice", "Bob", "Charlie"]
scores = [150, 120, 180]

with open("highscores.txt", "w") as my_file:
    for i in range(3):
        my_file.write(f"{names[i]},{scores[i]}\n")
print("Scores saved!")

Loading Scores

OCR Pseudocode:

myFile = openRead("highscores.txt")
while NOT myFile.endOfFile()
    line = myFile.readLine()
    parts = line.split(",")
    name = parts[0]
    score = int(parts[1])
    print(name + ": " + str(score))
endwhile
myFile.close()

Python:

with open("highscores.txt", "r") as my_file:
    for line in my_file:
        parts = line.strip().split(",")
        name = parts[0]
        score = int(parts[1])
        print(f"{name}: {score}")

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Worked Example: User Registration

OCR Pseudocode:

procedure registerUser()
    username = input("Choose a username: ")
    password = input("Choose a password: ")

    myFile = openWrite("users.txt")
    myFile.writeLine(username + "," + password)
    myFile.close()
    print("Registration successful!")
endprocedure

function checkLogin(enteredUser, enteredPass)
    myFile = openRead("users.txt")
    while NOT myFile.endOfFile()
        line = myFile.readLine()
        parts = line.split(",")
        if parts[0] == enteredUser AND parts[1] == enteredPass then
            myFile.close()
            return true
        endif
    endwhile
    myFile.close()
    return false
endfunction

Python:

def register_user():
    username = input("Choose a username: ")
    password = input("Choose a password: ")

    with open("users.txt", "a") as my_file:  # 'a' = append mode
        my_file.write(f"{username},{password}\n")
    print("Registration successful!")

def check_login(entered_user, entered_pass):
    with open("users.txt", "r") as my_file:
        for line in my_file:
            parts = line.strip().split(",")
            if parts[0] == entered_user and parts[1] == entered_pass:
                return True
    return False

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File Handling Summary Table

Operation	OCR Pseudocode	Python
Open for reading	openRead("file.txt")	open("file.txt", "r")
Open for writing	openWrite("file.txt")	open("file.txt", "w")
Read a line	file.readLine()	file.readline()
Write a line	file.writeLine(data)	file.write(data + "\n")
Check end of file	file.endOfFile()	Handled by for line in file
Close file	file.close()	file.close() or use with

The full lifecycle of a file from open through process to close can be summarised as:

flowchart TD
    A([Start]) --> B[openRead or openWrite filename]
    B --> C{Reading or Writing?}
    C -->|Reading| D[Loop while NOT endOfFile]
    D --> E[line = readLine]
    E --> F[Process line: cast, split, compare]
    F --> D
    C -->|Writing| G[writeLine data]
    G --> H{More data?}
    H -->|Yes| G
    H -->|No| I[close file]
    D -->|endOfFile true| I
    I --> J([End])

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Summary

• File handling allows data to persist between program executions.
• Use openRead() to read and openWrite() to write.
• Always close() files after use.
• readLine() reads one line; writeLine() writes one line.
• endOfFile() checks if you have reached the end of the file.

OCR Exam Tip: File handling questions on Paper 2 typically ask you to read data from a file and process it (e.g. count records, find a specific entry, calculate a total). Practise the OCR pseudocode syntax — openRead, readLine, endOfFile, and close are the key functions you must know.

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Worked Example: Processing a Log File

A school network stores login events in the text file login_log.txt. Each line contains a username followed by the number of minutes the user was logged in, separated by a comma (for example: "alice,45"). Write a program that reads this file and outputs the total minutes for a specific user.

OCR reference language pseudocode:

targetUser = input("Enter username to search: ")
totalMinutes = 0
found = false

myFile = openRead("login_log.txt")
while NOT myFile.endOfFile()
    line = myFile.readLine()
    parts = line.split(",")
    username = parts[0]
    minutes = int(parts[1])
    if username == targetUser then
        totalMinutes = totalMinutes + minutes
        found = true
    endif
endwhile
myFile.close()