C Academy · Lesson

Declaring Function Pointers

Pointers to functions.

Functions Have Addresses

Just like data, every function lives at an address in memory. A function pointer stores that address so you can call the function indirectly.

#include <stdio.h>

void greet(void) { printf("hello\n"); }

int main(void) {
    void (*fp)(void) = greet;
    fp();
    return 0;
}

The declaration int (*fp)(int) means: fp is a pointer to a function taking an int and returning an int.

The parentheses around *fp are required.

#include <stdio.h>

int square(int x) { return x * x; }

int main(void) {
    int (*fp)(int) = square;
    printf("%d\n", fp(5));
    return 0;
}