C Function Pointer

C Function Pointer

A function pointer in C language stores the address of a function and allows you to call a function indirectly.

Function pointers are the foundation of:

Callback functions
Dynamic behavior
Embedded systems
Operating systems
Standard library functions (like qsort)

Why Function Pointers Are Needed?

Dynamic function calling
Code flexibility & reusability
Callbacks implementation
Table-driven programming

Basic Syntax (Most Important)

Example

fp can point to any function returning int and taking two int arguments.

Simple Function Pointer Example (Beginner)

fp(5,3) is same as add(5,3)

Function Pointer with `typedef` (Clean Code)

Highly used in real projects
Makes code readable

Passing Function Pointer as Argument (Callback)

This is callback mechanism

Array of Function Pointers (Interview Favorite)

#include <stdio.h>

int add(int a, int b) { return a + b; }
int sub(int a, int b) { return a - b; }
int mul(int a, int b) { return a * b; }

int main() {
int (*ops[])(int, int) = {add, sub, mul};

printf("%d\n", ops[0](10, 5)); // add
printf("%d\n", ops[1](10, 5)); // sub
printf("%d\n", ops[2](10, 5)); // mul

return 0;
}

#include <stdio.h>

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

int sub(int a, int b) { return a - b; }

int mul(int a, int b) { return a * b; }

int main() {

int (*ops[])(int, int) = {add, sub, mul};

printf("%d\n", ops[0](10, 5)); // add

printf("%d\n", ops[1](10, 5)); // sub

printf("%d\n", ops[2](10, 5)); // mul

return 0;

}

Used in menu-driven programs
Used in compilers & OS

Function Pointer with `void *` (Advanced)

Generic programming
Library-level code

Function Pointer vs Normal Pointer

Feature	Data Pointer	Function Pointer
Points to	Variable	Function
Syntax	`int *p`	`int (*fp)()`
Used for	Data access	Code execution

Common Mistakes

Wrong parentheses

Correct

Passing function call instead of pointer

Real-Life Use Cases

Callbacks & event handling
qsort() comparison
Device drivers
Embedded interrupts
Plugin systems

Interview Questions (Must Prepare)

What is function pointer?
Why parentheses are required?
Difference between function pointer & normal pointer
Array of function pointers example
How callbacks are implemented?

Summary

Function pointers store function addresses
Essential for callbacks
Used in system-level programming
Very important for placements & interviews

C Function Pointer