File Handling

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Notes

What is File Handling?

**File handling** uses programming techniques to work with information stored in **text files**.
Common operations: **open**, **read**, **write**, and **close** files.
Files provide **permanent storage** for data beyond program execution.

Opening Files

Use `OPENFILE "filename" FOR READ` (pseudocode) or `open("filename", "r")` (Python) to **open for reading**.
Use `OPENFILE "filename" FOR WRITE` or `open("filename", "w")` to **open for writing** – creates new file or **overwrites** existing.
Use `OPENFILE "filename" FOR APPEND` or `open("filename", "a")` to **open for appending** – adds data to end of existing file.
Always **close** files after use with `CLOSEFILE` or `file.close()`.

Reading from Files

`READFILE "file", variable` (pseudocode) or `file.readline()` (Python) reads **one line** as a string.
Use a **loop** with an **end-of-file flag** to read all records.
`TRIM()` (pseudocode) or `.strip()` (Python) removes extra spaces/newlines from read data.
Check for empty string to detect end of file.

Writing to Files

`WRITEFILE "file", data` (pseudocode) or `file.write(data)` (Python) writes a string to the file.
Add `NEWLINE` (pseudocode) or `"\n"` (Python) to separate records/lines.
**Overwrite mode** (`"w"`) deletes existing content; **append mode** (`"a"`) preserves it.

Pseudocode Example (Reading)

Open file for read, set `endOfFile ← FALSE`.
Loop: read name, department, salary, age; trim each.
If name is empty, set `endOfFile ← TRUE`; else output details.
Close file after loop.

Python Example (Reading)

`file = open("employees.txt", "r")` then loop using `readline().strip()`.
Check `if name == "":` to set `endOfFile = True`.
Print fields and close file with `file.close()`.

Pseudocode Example (Writing/Appending)

Open file for append: `OPENFILE "employees.txt" FOR APPEND`.
Write each field on its own line, adding `NEWLINE` after each.
Close file when done.

Python Example (Writing/Appending)

`file = open("employees.txt", "a")` then `file.write("Polly\n")` etc.
Close file with `file.close()`.

Examiner Tips & Common Mistakes

Use correct mode letter: `"r"` for read, `"w"` for write (overwrites), `"a"` for append.
**Always close files** to avoid data loss or corruption.
Backup text files before testing – one mistake can lose contents.

Worked Example (CIE Style)

Input title and year from user.
Open `books.txt` for write (or append if preserving existing data).
Write title and year to file, then close.
Marks: input (1), open (1), write (1), close (1).

File handling operations as a sequence: Open → Read/Write → Close.

Practice questions

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1.What does the 'r' mode in file handling allow you to do?
Easy
- ARead from a file only
- BWrite to a new file
- CAppend to an existing file
- DRead and write to a file
2.Which file mode would you use to add data to the end of an existing file without overwriting it?
Easy
- A'w'
- B'a'
- C'r'
- D'x'
3.What is the purpose of the CLOSEFILE command in pseudocode?
Easy
- ATo delete the file from the disk
- BTo release the file from the program's control
- CTo clear all data in the file
- DTo open the file for reading
4.A program uses the pseudocode statement: OPENFILE "data.txt" FOR WRITE. What happens if "data.txt" already exists?
Medium
- AThe program appends data to the end of the file
- BThe program overwrites the existing contents of the file
- CThe program raises an error and stops
- DThe program reads the existing contents first
5.In the following pseudocode, what is the purpose of the variable endOfFile?
Medium
- ATo count the number of lines read
- BTo signal when there is no more data to read
- CTo store the last line of the file
- DTo indicate the size of the file
6.A text file contains employee records with each record spread over four lines: name, department, salary, age. Which pseudocode correctly reads one record?
Medium
- AREADFILE "employees.txt", name READFILE "employees.txt", department READFILE "employees.txt", salary READFILE "employees.txt", age
- BREADFILE "employees.txt", name, department, salary, age
- COPENFILE "employees.txt" FOR READ READFILE "employees.txt", name, department, salary, age
- DREADFILE "employees.txt", record SPLIT record INTO name, department, salary, age
7.Consider the pseudocode: OPENFILE "data.txt" FOR READ WHILE NOT EOF READFILE "data.txt", line IF line = "" THEN BREAK ENDIF OUTPUT line ENDWHILE CLOSEFILE "data.txt" What is the purpose of the IF statement checking for an empty line?
Hard
- ATo skip blank lines in the file
- BTo detect the end of the file
- CTo count the number of lines
- DTo remove empty lines from the output
8.Which Python statement correctly opens a file named 'students.txt' for appending?
Medium
- Afile = open('students.txt', 'a')
- Bfile = open('students.txt', 'w')
- Cfile = open('students.txt', 'r')
- Dfile = open('students.txt', 'append')

More questions

9.A text file 'scores.txt' contains numbers, one per line. Which pseudocode correctly calculates the total of all numbers?
Hard
- Atotal ← 0 OPENFILE "scores.txt" FOR READ READFILE "scores.txt", num WHILE num ≠ "" total ← total + num READFILE "scores.txt", num ENDWHILE CLOSEFILE "scores.txt"
- Btotal ← 0 OPENFILE "scores.txt" FOR READ READFILE "scores.txt", num WHILE num ≠ "" total ← total + CONVERT(num) READFILE "scores.txt", num ENDWHILE CLOSEFILE "scores.txt"
- Ctotal ← 0 OPENFILE "scores.txt" FOR READ WHILE NOT EOF READFILE "scores.txt", num total ← total + num ENDWHILE CLOSEFILE "scores.txt"
- Dtotal ← 0 OPENFILE "scores.txt" FOR READ READFILE "scores.txt", num total ← total + CONVERT(num) CLOSEFILE "scores.txt"
10.What does the TRIM function do in the pseudocode example?
Medium
- ARemoves the first character of a string
- BRemoves extra spaces and newline characters from the beginning and end of a string
- CConverts a string to uppercase
- DExtracts a portion of a string
11.Which file mode would you use to create a new file or overwrite an existing one?
Easy
- A'r'
- B'a'
- C'w'
- D'rw'
12.In the pseudocode for writing to a file, why is NEWLINE written after each field?
Hard
- ATo separate records so they can be read back correctly
- BTo make the file appear visually neat
- CTo increase file size
- DTo ensure the file is closed properly
13.A program reads data from a file named 'data.txt' using the following pseudocode: OPENFILE "data.txt" FOR READ WHILE NOT EOF READFILE "data.txt", line OUTPUT line ENDWHILE CLOSEFILE "data.txt" The file 'data.txt' contains the numbers 5, 10, and 15 each on a separate line. How many lines will be output?
Medium
- A3
- B2
- C4
- D1
14.A text file 'grades.txt' stores student grades in the format: name, grade, name, grade, ... each on separate lines. The following pseudocode is used to read the file and calculate the average grade: OPENFILE "grades.txt" FOR READ total = 0 count = 0 WHILE NOT EOF READFILE "grades.txt", name READFILE "grades.txt", grade total = total + grade count = count + 1 ENDWHILE CLOSEFILE "grades.txt" average = total / count What is the output if the file contains: Anna 85 Ben 92 ?
Hard
- A88.5
- B85
- C92
- DError: cannot divide by zero
15.Which Python statement correctly opens a file named 'data.txt' for reading?
Easy
- Afile = open("data.txt", "r")
- Bfile = open("data.txt", "w")
- Cfile = open("data.txt", "a")
- Dfile = open("data.txt", "read")
16.A program uses the following pseudocode to write to a file: OPENFILE "output.txt" FOR WRITE WRITEFILE "output.txt", "Hello" WRITEFILE "output.txt", NEWLINE WRITEFILE "output.txt", "World" CLOSEFILE "output.txt" What will the file contain after execution?
Medium
- AHello World
- BHelloWorld
- CHello World
- DHello World
17.A text file 'scores.txt' contains the following numbers, one per line: 10 20 30 40 Which pseudocode correctly calculates the sum of all numbers?
Hard
- Atotal = 0 OPENFILE "scores.txt" FOR READ WHILE NOT EOF READFILE "scores.txt", num total = total + num ENDWHILE CLOSEFILE "scores.txt"
- Btotal = 0 OPENFILE "scores.txt" FOR READ FOR i = 1 TO 4 READFILE "scores.txt", num total = total + num ENDFOR CLOSEFILE "scores.txt"
- Ctotal = 0 OPENFILE "scores.txt" FOR READ REPEAT READFILE "scores.txt", num total = total + num UNTIL EOF CLOSEFILE "scores.txt"
- Dtotal = 0 OPENFILE "scores.txt" FOR READ WHILE NOT EOF READFILE "scores.txt", num total = total + 1 ENDWHILE CLOSEFILE "scores.txt"
18.What is the purpose of the TRIM function in the pseudocode example for reading employee data?
Medium
- ATo remove extra spaces and newline characters from the read data
- BTo convert the data to uppercase
- CTo check if the data is empty
- DTo split the data into separate fields
19.Which file mode should be used to add data to the end of an existing file without deleting its current contents?
Easy
- AAPPEND
- BWRITE
- CREAD
- DUPDATE
20.Consider the following pseudocode: OPENFILE "data.txt" FOR READ WHILE NOT EOF READFILE "data.txt", line IF line = "" THEN BREAK ENDIF OUTPUT line ENDWHILE CLOSEFILE "data.txt" What will be output if the file contains: apple banana ?
Medium
- Aapple
- Bapple banana
- Capple banana
- Dapple banana
21.A file 'data.txt' contains the following records, each on a separate line: ID:101 Name:Alice Score:85 ID:102 Name:Bob Score:92 Which pseudocode correctly reads all records and outputs the name of each student?
Hard
- AOPENFILE "data.txt" FOR READ WHILE NOT EOF READFILE "data.txt", id READFILE "data.txt", name READFILE "data.txt", score OUTPUT name ENDWHILE CLOSEFILE "data.txt"
- BOPENFILE "data.txt" FOR READ WHILE NOT EOF READFILE "data.txt", line IF line CONTAINS "Name:" THEN OUTPUT line ENDIF ENDWHILE CLOSEFILE "data.txt"
- COPENFILE "data.txt" FOR READ FOR i = 1 TO 2 READFILE "data.txt", id READFILE "data.txt", name READFILE "data.txt", score OUTPUT name ENDFOR CLOSEFILE "data.txt"
- DOPENFILE "data.txt" FOR READ WHILE NOT EOF READFILE "data.txt", id READFILE "data.txt", name READFILE "data.txt", score IF id CONTAINS "ID" THEN OUTPUT name ENDIF ENDWHILE CLOSEFILE "data.txt"
22.What does the CLOSEFILE command do?
Easy
- AIt closes the file and releases system resources
- BIt deletes the file from the disk
- CIt saves the file to a new location
- DIt clears the contents of the file
23.A program opens a file with OPENFILE "data.txt" FOR WRITE. What happens if the file already exists?
Medium
- AThe existing contents are overwritten
- BThe new data is appended to the end
- CAn error occurs and the file is not opened
- DThe file is renamed and a new file is created
24.A text file 'log.txt' contains timestamps and events. Each line has a timestamp followed by a space and an event. Which pseudocode correctly counts the number of events that contain the word 'ERROR'?
Hard
- Acount = 0 OPENFILE "log.txt" FOR READ WHILE NOT EOF READFILE "log.txt", line IF line CONTAINS "ERROR" THEN count = count + 1 ENDIF ENDWHILE CLOSEFILE "log.txt"
- Bcount = 0 OPENFILE "log.txt" FOR READ WHILE NOT EOF READFILE "log.txt", line IF line = "ERROR" THEN count = count + 1 ENDIF ENDWHILE CLOSEFILE "log.txt"
- Ccount = 0 OPENFILE "log.txt" FOR READ WHILE NOT EOF READFILE "log.txt", timestamp READFILE "log.txt", event IF event = "ERROR" THEN count = count + 1 ENDIF ENDWHILE CLOSEFILE "log.txt"
- Dcount = 0 OPENFILE "log.txt" FOR READ WHILE NOT EOF READFILE "log.txt", line IF line INCLUDES "ERROR" THEN count = count + 1 ENDIF ENDWHILE CLOSEFILE "log.txt"
25.A school uses a text file to store student names and marks, one record per line in the format 'Name,Mark'. Which pseudocode correctly reads the file and outputs the name and mark for each student?
Medium
- AOPENFILE "students.txt" FOR READ WHILE NOT EOF READFILE "students.txt", line name ← line[1] mark ← line[2] OUTPUT name, mark ENDWHILE CLOSEFILE "students.txt"
- BOPENFILE "students.txt" FOR READ WHILE NOT EOF READFILE "students.txt", name READFILE "students.txt", mark OUTPUT name, mark ENDWHILE CLOSEFILE "students.txt"
- COPENFILE "students.txt" FOR READ WHILE NOT EOF READFILE "students.txt", line name ← TRIM(line) mark ← TRIM(line) OUTPUT name, mark ENDWHILE CLOSEFILE "students.txt"
- DOPENFILE "students.txt" FOR READ WHILE NOT EOF READFILE "students.txt", line name ← SUBSTRING(line, 1, COMMA_POS-1) mark ← SUBSTRING(line, COMMA_POS+1) OUTPUT name, mark ENDWHILE CLOSEFILE "students.txt"
26.A file 'log.txt' contains multiple lines of text. The following pseudocode is intended to count the number of lines that contain the word 'ERROR'. Which line of pseudocode is missing? OPENFILE "log.txt" FOR READ count ← 0 WHILE NOT EOF READFILE "log.txt", line line ← TRIM(line) IF line CONTAINS "ERROR" THEN count ← count + 1 ENDIF ENDWHILE CLOSEFILE "log.txt" OUTPUT count
Medium
- AA statement to initialise count to 0 is missing before the loop.
- BA statement to close the file is missing after the loop.
- CA statement to set endOfFile flag is missing inside the loop when line is empty.
- DNo line is missing; the pseudocode is correct.
27.A programmer writes the following Python code to read from a file: file = open("data.txt", "r") for line in file: print(line.strip()) file.close() What is the main advantage of using a 'for line in file' loop over a 'while not endOfFile' loop with readline()?
Hard
- AThe for loop automatically handles closing the file.
- BThe for loop is faster because it reads the entire file at once.
- CThe for loop automatically stops at the end of the file without needing an explicit check.
- DThe for loop can only be used with text files, not binary files.
28.What is the purpose of the TRIM function in the pseudocode for reading employee data from a text file?
Easy
- ATo remove any leading and trailing spaces or newline characters from the string.
- BTo cut the string to a specified length.
- CTo convert the string to uppercase.
- DTo check if the string is empty.
29.A text file 'marks.txt' contains student marks, one per line. The following pseudocode reads the file and outputs the average mark. Which line contains an error? 1 OPENFILE "marks.txt" FOR READ 2 total ← 0 3 count ← 0 4 WHILE NOT EOF 5 READFILE "marks.txt", mark 6 total ← total + mark 7 count ← count + 1 8 ENDWHILE 9 CLOSEFILE "marks.txt" 10 average ← total / count 11 OUTPUT average
Medium
- ALine 2: total should be initialised to 0.0
- BLine 6: mark is a string, so it cannot be added to total without conversion.
- CLine 10: average should be calculated inside the loop.
- DLine 11: OUTPUT should be PRINT.
30.A program needs to add new records to the end of an existing file without deleting any existing data. Which file mode should be used?
Medium
- AREAD
- BWRITE
- CAPPEND
- DUPDATE
31.A text file 'records.txt' stores data in the format: each record occupies 3 lines (ID, Name, Score). The following pseudocode is intended to read all records and output the name of the student with the highest score. Which line contains a logical error? 1 OPENFILE "records.txt" FOR READ 2 maxScore ← -1 3 maxName ← "" 4 WHILE NOT EOF 5 READFILE "records.txt", id 6 READFILE "records.txt", name 7 READFILE "records.txt", score 8 IF score > maxScore THEN 9 maxScore ← score 10 maxName ← name 11 ENDIF 12 ENDWHILE 13 CLOSEFILE "records.txt" 14 OUTPUT maxName
Hard
- ALine 2: maxScore should be initialised to 0.
- BLine 8: score is a string, so comparison may not work as expected.
- CLine 5: id is not used, so it should be omitted.
- DLine 14: OUTPUT should be PRINT.
32.In the pseudocode for writing employee data to a file, why is NEWLINE written after each field?
Medium
- ATo separate fields within a record so that each field appears on a new line.
- BTo mark the end of the file.
- CTo add blank lines for readability.
- DTo prevent the file from being overwritten.
33.A program uses the following pseudocode to read a file 'data.txt' that contains numbers, one per line. It is supposed to output the sum of all numbers. However, it outputs 0. What is the most likely cause? OPENFILE "data.txt" FOR READ sum ← 0 WHILE NOT EOF READFILE "data.txt", num sum ← sum + num ENDWHILE CLOSEFILE "data.txt" OUTPUT sum
Hard
- AThe variable sum should be initialised to 0.0 instead of 0.
- BThe file 'data.txt' does not exist, so the OPENFILE fails silently.
- CThe variable num is a string, so the addition concatenates strings instead of adding numbers.
- DThe WHILE loop never executes because EOF is true at the start.
34.What does the command OPENFILE do in pseudocode?
Easy
- AIt creates a connection to a file so that it can be read from or written to.
- BIt displays the contents of a file on the screen.
- CIt deletes the file from the storage device.
- DIt checks whether a file exists without opening it.
35.Which pseudocode command is used to close a file after processing?
Easy
- ACLOSEFILE
- BEND
- CSTOP
- DEXIT
36.In pseudocode, what is the purpose of the TRIM function when reading data from a file?
Medium
- AIt removes extra spaces and newline characters from the beginning and end of a string.
- BIt cuts the string to a specified length.
- CIt converts the string to uppercase.
- DIt checks if the string is empty.
37.A text file 'students.txt' stores each student's name and age on separate lines, repeating for all students. Which pseudocode correctly reads all records and outputs the names?
Hard
- AOPENFILE "students.txt" FOR READ endOfFile ← FALSE WHILE NOT endOfFile DO READFILE "students.txt", name name ← TRIM(name) READFILE "students.txt", age age ← TRIM(age) IF name = "" THEN endOfFile ← TRUE ELSE OUTPUT name ENDIF ENDWHILE CLOSEFILE "students.txt"
- BOPENFILE "students.txt" FOR READ WHILE NOT EOF READFILE "students.txt", line OUTPUT line ENDWHILE CLOSEFILE "students.txt"
- COPENFILE "students.txt" FOR READ REPEAT READFILE "students.txt", name OUTPUT name READFILE "students.txt", age UNTIL EOF CLOSEFILE "students.txt"
- DOPENFILE "students.txt" FOR READ FOR i ← 1 TO 10 READFILE "students.txt", name OUTPUT name ENDFOR CLOSEFILE "students.txt"
38.Consider the following pseudocode: OPENFILE "data.txt" FOR WRITE WRITEFILE "data.txt", "Hello" WRITEFILE "data.txt", NEWLINE WRITEFILE "data.txt", "World" CLOSEFILE "data.txt" What will be the contents of 'data.txt'?
Medium
- AHello World
- BHelloWorld
- CHello World
39.In Python, which mode string should be used to open a file for reading?
Easy
- A"r"
- B"w"
- C"a"
- D"rw"
40.What happens if you open a file in write mode ("w") in Python and the file already exists?
Easy
- AThe existing contents are erased and the file is overwritten.
- BNew data is appended to the end of the file.
- CAn error occurs and the file is not opened.
- DThe file is opened but no operations are allowed.

Slides

What is File Handling?

File handling is the use of programming techniques to work with information stored in text files.
Common operations: opening, reading, writing, and closing files.
Files allow data to be stored permanently, unlike variables which lose data when the program ends.

Opening and Closing Files

Open a file with OPENFILE in pseudocode or open() in Python.
Modes: FOR READ ("r"), FOR WRITE ("w"), FOR APPEND ("a").
Always close a file with CLOSEFILE or file.close() to save changes and free resources.

Which mode should you use to add data to the end of an existing file without deleting its current contents?

FOR READ
FOR WRITE
FOR APPEND
FOR UPDATE

Reading from a File

Use READFILE in pseudocode or file.readline() in Python to read one line at a time.
Each read returns a string; use TRIM() or .strip() to remove extra spaces/newlines.
A common pattern: read until end-of-file, checking for an empty string.

To read a line from a file in Python, use the method ____.

Writing to a File

Use WRITEFILE in pseudocode or file.write() in Python to write data.
In write mode ("w"), a new file is created; if it exists, it is overwritten.
In append mode ("a"), data is added to the end of the file.
Add newline characters (NEWLINE or "\n") to separate records.

What happens if you open an existing file with FOR WRITE ("w")?

The file is opened and new data is appended to the end.
The file is opened and its existing contents are deleted.
An error occurs because the file already exists.
The file is opened in read-only mode.

Pseudocode Example: Reading Data

A text file stores employee records: each record spans 4 lines (name, department, salary, age).
Open the file, then loop reading lines until end-of-file (empty name).
Trim each line, output the fields, and close the file.

Which of these are true about reading from a file?

READFILE reads one line at a time.
TRIM() removes leading and trailing spaces/newlines.
You must know the number of lines in advance to read a file.
An empty string indicates the end of the file.

Pseudocode Example: Writing Data

To add a new employee record, open the file in append mode.
Write each field on its own line, adding NEWLINE after each.
Close the file to save changes.

In pseudocode, to write a line of text to a file you use the command ____.

Python Example: Reading Data

Open file with open("employees.txt", "r").
Use a while loop: read lines with .readline().strip().
Check for empty string to detect end-of-file.
Print the fields and close the file with .close().

In Python, what does the .strip() method do when reading a line from a file?

Removes all spaces from the string.
Removes leading and trailing whitespace (including newline).
Converts the string to lowercase.
Splits the string into a list.

Python Example: Writing Data

Open file with open("employees.txt", "a") to append.
Use .write() to write each field, adding "\n" for newline.
Close the file with .close().

In Python, to open a file for appending you use the mode string ____.

Examiner Tips and Tricks

Use the correct mode: "r" for read, "w" for write, "a" for append.
Writing with "w" overwrites the entire file – be careful!
Always back up important text files before testing your code.

Which of the following is a risk of using FOR WRITE ("w") mode?

The file may not exist.
The file contents may be accidentally deleted.
The file cannot be read afterwards.
The file size increases.

Worked Example: Storing Book Details

Task: Input title and year, store them in an existing file books.txt.
Steps: Input title, input year, open file for write, write title, write year, close file.
Mark scheme: 1 mark for inputs, 1 for opening file, 1 for writing, 1 for closing.

In the worked example, after writing the title and year, you must ____ the file.

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