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)

1️⃣ Why Function Pointers Are Needed?

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

2️⃣ Basic Syntax ⭐ (Most Important)

Example

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

3️⃣ Simple Function Pointer Example (Beginner)

📌 fp(5,3) is same as add(5,3)

4️⃣ Function Pointer with `typedef` (Clean Code ⭐)

✔ Highly used in real projects
✔ Makes code readable

5️⃣ Passing Function Pointer as Argument (Callback)

🔥 This is callback mechanism

6️⃣ 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

7️⃣ Function Pointer with `void *` (Advanced)

✔ Generic programming
✔ Library-level code

8️⃣ 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

9️⃣ 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