Add element in Linked List

struct node
{
    int data;
    struct node *link;
} *head;

void add_beginning (int num) {
    struct node *temp;
    temp = (struct node *)malloc(sizeof(struct node));
    temp ->data = num;
    temp ->link = NULL;

    if (head == NULL) {
        head = temp;
   }
   else {
       temp ->link = head;
       head = temp;
   }
}

void add_end (int num) {
    struct node *temp;
    temp = (struct node *)malloc(sizeof(struct node));
    temp ->data = num;
    temp ->link = NULL;

    if (head == NULL){
          head = temp;
    }
    else {
         right = (struct node *)head;
         while(right ->link != NULL)
              right = right ->link;
         right ->link = temp;
    }
}         

Void add_middle (int c, int num){
    struct node *temp;
    temp = (struct node *)malloc(sizeof(struct node));
    temp ->data = num;
    temp ->link = NULL;
   
     if (head == NULL){
          head = temp;
    }
    else {
        struct node *right, *right1;
        right = head;
         right1 = head;
         for (int i = 0; i <c; i++)
             right = right ->link;
           
       right1 = right ->next;
       right ->next = temp;
       temp ->next = right1;
     } 
 }