Pointers to Functions in C

So far, you have learned pointers to variables and pointers to arrays.

In this lesson, we take one more powerful step: pointers to functions.

This concept allows a function to be treated like data.

Do not rush. Read slowly. This lesson is simpler than it looks.

Why Do We Need Function Pointers?

Normally, we call functions directly:

add(10, 20);

But sometimes we want to:

• Decide which function to call at runtime
• Pass a function as an argument
• Create flexible and reusable code

This is where function pointers are used.

Function Name Is a Pointer

Just like arrays, a function name represents the address of the function.

That means we can store a function’s address in a pointer.

Basic Syntax of Function Pointer

General format:

return_type (*pointer_name)(parameter_types);

Yes, the syntax looks strange — but the logic is simple.

Simple Example

#include <stdio.h>

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

int main() {
    int (*ptr)(int, int);
    ptr = add;

    printf("%d", ptr(5, 3));
    return 0;
}

Explanation:

• add is the function
• ptr stores its address
• ptr(5,3) calls the function

Calling Function Using Pointer

These two calls are equivalent:

add(5, 3);
ptr(5, 3);

The compiler treats both the same.

Real-World Example

Imagine a remote control:

• Buttons do not perform work
• They point to actions

Function pointers work the same way. They point to different functions dynamically.

Using Function Pointers with Multiple Functions

#include <stdio.h>

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

int main() {
    int (*operation)(int, int);

    operation = add;
    printf("Add: %d\n", operation(10, 5));

    operation = subtract;
    printf("Subtract: %d\n", operation(10, 5));

    return 0;
}

Same pointer, different behavior.

Where Are Function Pointers Used?

• Callbacks
• Event handling
• Sorting algorithms
• Menu-driven programs
• Operating systems

Common Mistakes

• Wrong function signature
• Missing parentheses in pointer declaration
• Confusing function call and pointer call

Mini Practice

• Create two functions (multiply, divide)
• Use a function pointer to call both
• Print results

Quick Quiz

Q1. What does a function pointer store?

Address of a function.

Q2. Why are parentheses important in function pointers?

They ensure correct binding of pointer to function signature.

Q3. Can a function pointer point to different functions?

Yes, as long as signatures match.

Q4. Where are function pointers commonly used?

Callbacks, menus, event systems, sorting.

Q5. Are function pointers advanced or basic?

They are fundamental for advanced C programming.