In this example, passing a pointer to structure to a function is not working, whereas declaring it globally would work fine. Why?

Question

I am learning pointers and structures in C.

In this process I am stuck with a problem, consider the following code :

#include <stdio.h>
#include <stdlib.h>

struct data{
    int i;
};

void test(struct data *, int);

int main(){

    struct data *head = NULL;

    test(head, 100);
    printf("head->i :%d\n",head->i); // Should print 100, but it's NOT.
    return 0;
}


void test(struct data *head, int i){
    struct data *new = (struct data *)malloc(sizeof(struct data));
    new->i = 10;
    head = new;
}

But instead of printing 100, the programming is throwing a Segmentation Fault.

When I modify the code as follows :

#include <stdio.h>
#include <stdlib.h>

struct data{
    int i;
};

struct data *head = NULL;

void test(int );

int main(){

    test(100);
    printf("head->i :%d\n",head->i); // It prints 100 WITH EASE!
    return 0;
}


void test(int i){
    struct data *new = (struct data *)malloc(sizeof(struct data));
    new->i = 10;
    head = new;
}

All I did in the above code was declare the head pointer globally.

How does that make any difference?

Can someone please explain me Why?