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🧠 Week 5 – Files & Modular Programming

This week we explore file input/output (I/O) and modular program design in C.
You will learn to read and write files, store structured data, and create a simple management system that persists between runs.

🧾 Task 1: Read and Write Data from Files

Implement

Create a C program week5_task1_file_io.c that:

  1. Opens a text file for writing (e.g., "data.txt").
  2. Writes a few lines of text into it using fprintf().
  3. Closes the file properly.
  4. Opens the same file again for reading.
  5. Reads its contents line by line using fgets() and prints them to the console.

Use the provided stub file:

week5_task1_file_io.c

Rules

  • Always check that the file pointer returned by fopen() is not NULL.
  • Use clear messages to indicate whether you are writing or reading.
  • Close every opened file using fclose().
  • Avoid hardcoding long text — optionally read input from the user.
  • Ensure your program compiles without warnings using -Wall.

Example

$ ./week5_task1_file_io
Writing lines to data.txt...
Reading contents:
Hello, file I/O in C!
This is another line.

🧾 Task 2: Save and Load Structured Records

Implement

Create a C program week5_task2_struct_save_load.c that:

  1. Defines a struct Student containing a name, age, and GPA.
  2. Saves one student record to a text file using a helper function save_student().
  3. Loads that record from the file using another function load_student().
  4. Prints the loaded record to confirm that it matches the original.

Use the provided stub file:

week5_task2_struct_save_load.c

Rules

  • Implement both save_student() and load_student() with proper file checking.
  • Save the data in a simple text format: name age gpa.
  • Use fprintf() and fscanf() for writing and reading.
  • Avoid using global variables.
  • Handle cases when the file cannot be opened.

Example

$ ./week5_task2_struct_save_load
Saving student to file...
Loading student from file...
Loaded student: Alice, 21, GPA 3.75

🧾 Task 3: Mini-Project – Student Management System with File Persistence

Implement

Create a C program week5_task3_student_management_system.c that:

  1. Allows listing, adding, and saving students.
  2. Uses an array of struct Student to store data in memory.
  3. Loads existing data from a file at startup.
  4. Saves all students back to the file before exiting.
  5. Displays a simple text-based menu with options (list/add/save-exit).

Use the provided stub file:

week5_task3_student_management_system.c

Rules

  • Implement all functions marked TODO in the stub:
    • load_students()
    • save_students()
    • add_student()
    • list_students()
  • Use text file storage (students.txt) and one line per record.
  • Ensure program handles empty files gracefully.
  • Maintain clean and readable code with comments.
  • Compile without warnings using the provided Makefile.

Example

=== Student Management System ===
1. List students
2. Add student
3. Save and Exit
Select an option: 2
Enter name: Alice
Enter ID: 101
Enter GPA: 3.8
Student added successfully!

=== Student Management System ===
1. List students
2. Add student
3. Save and Exit
Select an option: 3
Data saved. Goodbye!

💾 Bonus Task 4: Binary File Version (Advanced)

Implement

Extend Task 2 to save and load struct Student records in binary format using fwrite() and fread().

Create a new file:

week5_task4_struct_binary_io.c

Your program should:

  1. Define the same struct Student as in Task 2.
  2. Save the struct directly in binary format.
  3. Load the struct back and print its contents.
  4. Compare file sizes between text and binary versions.

Rules

  • Use modes "wb" (write binary) and "rb" (read binary).
  • Use fwrite(&student, sizeof(Student), 1, fp);
  • Use fread(&student, sizeof(Student), 1, fp);
  • Print confirmation messages during save and load.
  • Check file pointer validity before any file operations.

Example

$ ./week5_task4_struct_binary_io
Saving student in binary format...
Loading student from binary file...
Loaded student: Alice, 21, GPA 3.75
Binary file size: 60 bytes

🛠️ Makefile

You can compile all tasks with:

make

Run individual programs with:

make run1
make run2
make run3

Clean all executables:

make clean

📚 Authoritative Resources

File I/O in C

Structs and Modular Programming

Binary Files

✅ Learning Outcomes

After completing Week 5, you will be able to:

  • Read and write data to text and binary files in C.
  • Persist and reload structured records using struct.
  • Implement a small modular project with file persistence.
  • Understand how to separate code into multiple functions and files.
  • Compare text and binary file storage formats.

🧩 Submission Instructions

Students can submit their completed Week 5 work in one or BOTH of the following ways:

Option A – Submit GitHub Repository URL

If you have been working in GitHub Codespaces or using your forked course repository:

  1. Ensure all your Week 5 source files are committed and pushed to your repository.
  2. Include the following files in your repository under the src/ folder (or equivalent):
    • week5_task1_file_io.c
    • week5_task2_struct_save_load.c
    • week5_task3_student_management_system.c
    • (optional) week5_task4_struct_binary_io.c
  3. Provide a URL link to your GitHub repository in the Moodle submission field.
  4. Make sure your repository is public or accessible to the instructor.

Option B – Upload Source Files Directly to Moodle

If you prefer, you may submit the actual source code files directly:

  1. Upload your .c files for all tasks as separate attachments.
  2. Each file must include:
    • A comment at the top with your Name, Surname, and Student ID.
    • Optional: a link to your GitHub repository.
    • Compilation instructions if special flags are required.
  3. Check that each program compiles without errors or warnings using: 
    make lab5