Introduction to Programming in C

📘 Advanced Pointers in C (Pointer to Pointer, Function Pointers)

In this chapter, we explore more powerful applications of pointers: Pointer to Pointer and Function Pointers. These are essential for mastering dynamic memory, arrays of strings, callbacks, and low-level programming.

🔹 Pointer to Pointer (Double Pointer)

A pointer to pointer is a variable that stores the address of another pointer. It's especially useful when dealing with 2D arrays, dynamic memory, or passing pointers by reference.

int a = 10;
int *p = &a;
int **pp = &p;

printf("Value of a: %d\n", a);
printf("Value via *p: %d\n", *p);
printf("Value via **pp: %d\n", **pp);

📦 Use Case: Changing Pointer from Function

void updatePointer(int **pp) {
  static int x = 50;
  *pp = &x;
}

int main() {
  int *p;
  updatePointer(&p);
  printf("Updated value: %d\n", *p);  // Output: 50
}

🔧 Function Pointers

Function pointers are used to point to functions. You can invoke a function via a pointer. They are widely used in callbacks, menu-driven programs, and implementing dynamic behavior.

int add(int a, int b) {
  return a + b;
}

int main() {
  int (*fptr)(int, int);
  fptr = add;
  printf("Sum = %d\n", fptr(3, 5));  // Output: 8
}

📚 UdaanPath Example: Menu System with Function Pointers

void menu() {
  printf("1. Home\n2. Courses\n3. Exit\n");
}

void courses() {
  printf("Available courses at UdaanPath...\n");
}

int main() {
  void (*actions[2])() = {menu, courses};

  actions[0]();  // Calls menu
  actions[1]();  // Calls courses
  return 0;
}

💡 Why Use Function Pointers?

• To pass functions as arguments to other functions
• To implement callback mechanisms
• To write plugin systems or event handlers
• To build table-driven code (e.g., command handlers)

📝 Practice Exercises

1. Declare and use a pointer to pointer for an integer variable
2. Write a function that receives a pointer to pointer and modifies it
3. Create an array of function pointers for a calculator (add, sub, mul, div)
4. Simulate a menu system using function pointers

✅ Summary

• Pointer to pointer stores the address of another pointer
• Useful for dynamic memory and modifying pointers inside functions
• Function pointers allow calling functions dynamically
• Used in callbacks, event handling, and modular code execution

🚀 Coming Next

In the next chapter, we'll cover Linked Lists — dynamic data structures that are the building blocks of advanced algorithms.