recursion"what is the output of the program"

Question

#include <stdio.h>
void fun(int);
typedef int (*pf) (int ,int );
int proc(pf, int ,int);

int main()
{
    int a = 3;
    fun(a);
    return 0;
    
}

void fun(int n)
{
    if (n>0)
    {
    fun(--n);
    printf("%d,", n);
    fun(--n);
}
}

Comments

typedef int (*pf) (int ,int );
int proc(pf, int ,int);

what is the use of this function declarations?? 

---

check this, it may help https://gateoverflow.in/232891/test-series

---

0,1,2,0