#include<stdio.h>

void A(int a)
{
    printf("I am in function A and here's a: %dn", a);
}

// callback function
void B(void (*ptr)(int b) )
{
//    int b = 5;
    int b;
    printf("I am in function B and b = %dn", b);
    (*ptr) (b); // callback to A
}

int main()
{
    int c = 6;
    void (*ptr)(int c) = &A;

    // calling function B and passing
    // address of the function A as argument
    B(ptr);

   return 0;
}