how to pass pointer function as argument in c code example

Example 1: c function pointer in argument

void f(void (*a)()) {
    a();
}

void test() {
    printf("hello world\n");
}

int main() {
     f(&test);
     return 0;
}

Example 2: how to use a pointer as a parameter in c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
void add(int* a, int* b, int* c)
{
    *c = *a + *b;
}
int main()
{
	int a, b, c;
	a = 3;
	b = 5;
	add(&a, &b, &c);
	printf("%d", c);
}