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🧩 Week 4 – Dynamic Memory & Structures

This week focuses on using pointers for dynamic memory allocation, creating and using structures, and combining both ideas to build a small in-memory database.
All programs should compile cleanly without warnings using the provided Makefile.

🧠 Task 1 – Create Dynamic Arrays with malloc

Implement

Write a C program that:

  • Asks the user for the number of elements.
  • Dynamically allocates memory for an integer array using malloc.
  • Reads integers from user input and stores them in the array.
  • Calculates and prints the sum and average of the entered numbers.
  • Frees all allocated memory before the program exits.

The file should be named:
src/week4_1_dynamic_array.c

Rules

  • Always check if malloc returned a valid pointer.
  • Use sizeof(int) when allocating memory.
  • Avoid memory leaks: every successful malloc should have a corresponding free.
  • Use clear, formatted output with printf.

Example

Enter number of elements: 5
Enter 5 integers: 10 20 30 40 50
Sum = 150
Average = 30.00

🎓 Task 2 – Define and Use a struct (Student Record)

Implement

Write a C program that defines and uses a structure called Student.
Each student has:

  • char name[50]
  • int id
  • float grade

The program should:

  • Declare at least two Student variables.
  • Assign values to their fields (either manually or through user input).
  • Print the information of each student in a formatted way.

The file should be named:
src/week4_2_struct_student.c

Rules

  • Use struct keyword for the definition.
  • Access fields using the dot (.) operator.
  • You may use strcpy() to assign a string to the name field.
  • Keep output readable and labeled.

Example

Student 1: Alice Johnson, ID: 1001, Grade: 9.1
Student 2: Bob Smith, ID: 1002, Grade: 8.7

🗂️ Task 3 – Build an In-Memory Database (Array of Structs)

Implement

Create a C program that:

  • Defines a struct Student (same as in Task 2).
  • Dynamically allocates memory for an array of Student records using malloc.
  • Prompts the user for the number of students.
  • Reads each student’s name, ID, and grade from the user.
  • Prints all student records in a formatted table.
  • Frees all allocated memory before exit.

The file should be named:
src/week4_3_struct_database.c

Rules

  • Reuse your struct Student definition from Task 2.
  • Use malloc(n * sizeof(struct Student)) for allocation.
  • Remember to use scanf("%s", student[i].name) for names (no spaces) or fgets() for full names.
  • Free the allocated memory before program termination.
  • Consider sorting or computing averages as optional bonus.

Example

Enter number of students: 3
Enter data for student 1: Alice 1001 9.1
Enter data for student 2: Bob 1002 8.7
Enter data for student 3: Carol 1003 9.5

ID     Name        Grade
1001   Alice       9.1
1002   Bob         8.7
1003   Carol       9.5

💾 Submission Instructions

Students can submit their work in either of two ways or BOTH:

Option A – Submit Repository URL

  1. Ensure your GitHub repository is up to date: 
    git add .
git commit -m "Week 4 completed"
git push
  2. Submit the URL to your GitHub repository in Moodle.
    Example: 
    https://github.com/yourusername/RTU_Programming_Languages_C_Lab_Fall_2025

Option B – Submit Source Files

  1. Download your source files from the Codespaces src/ folder:
    • week4_1_dynamic_array.c
    • week4_2_struct_student.c
    • week4_3_struct_database.c
  2. Upload these .c files directly to Moodle.

Again, I prefer option A, but you can do option B if you are having trouble with your git repository.

📚 Web Resources on Dynamic Memory & Structs in C

Note: Some of these are not formal, but should provide a reasonable overview.

Dynamic Memory Allocation

Structures (struct)

✅ Reminder:

  • Your code must compile without warnings using the provided Makefile.
  • Comment your code clearly — explain why each important step is done.
  • Always free dynamically allocated memory.
  • Programs that crash or leak memory will lose points.