insert fisrst in liked list

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

struct Node {
    int data;
    struct Node* next;
};

// Program to create a simple linked
// list with 3 nodes
int main()
{
    struct Node* head = NULL;
    struct Node* newnode = NULL;
    struct Node* second = NULL;
    struct Node* third = NULL;
    struct Node* temp = NULL;

    // allocate 3 nodes in the heap
    head = (struct Node*)malloc(sizeof(struct Node));
    newnode = (struct Node*)malloc(sizeof(struct Node));
    second = (struct Node*)malloc(sizeof(struct Node));
    third = (struct Node*)malloc(sizeof(struct Node));

    /* Three blocks have been allocated dynamically.
    We have pointers to these three blocks as first,
    second and third
    head         second      third
        |            |           |
        |            |           |
    +---+-----+  +----+----+     +----+----+
    | # | # |    | # | # |   | # | # |
    +---+-----+  +----+----+     +----+----+

# represents any random value.
Data is random because we haven’t assigned
anything yet */

    head->data = 1; // assign data in first node
    head->next = second; // Link first node with
    // the second node

    /* data has been assigned to the data part of the first
    block (block pointed by the head). And next
    pointer of first block points to second.
    So they both are linked.

    head         second      third
        |            |           |
        |            |           |
    +---+---+    +----+----+     +-----+----+
    | 1 | o----->| # | # |   | # | # |
    +---+---+    +----+----+     +-----+----+
*/

    // assign data to second node
    second->data = 2;

    // Link second node with the third node
    second->next = third;

    /* data has been assigned to the data part of the second
    block (block pointed by second). And next
    pointer of the second block points to the third
    block. So all three blocks are linked.

    head         second      third
        |            |           |
        |            |           |
    +---+---+    +---+---+   +----+----+
    | 1 | o----->| 2 | o-----> | # | # |
    +---+---+    +---+---+   +----+----+     */

    third->data = 3; // assign data to third node
    third->next = NULL;

    /* data has been assigned to data part of third
    block (block pointed by third). And next pointer
    of the third block is made NULL to indicate
    that the linked list is terminated here.

    We have the linked list ready.

        head
            |
            |
        +---+---+    +---+---+   +----+------+
        | 1 | o----->| 2 | o-----> | 3 | NULL |
        +---+---+    +---+---+   +----+------+


    Note that only head is sufficient to represent
    the whole list. We can traverse the complete
    list by following next pointers. */
    newnode->data = 100; // assign data in first node
    newnode->next = head;

    temp=newnode;
    while (temp != 0)
    {
        printf("[%d]   [%d]",newnode,temp->data);

        temp = temp->next;
    }
    printf("[null]");
    return 0;
}