Linked list operations

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

struct node
{
    int data;
    struct node *next;
} *start=NULL;

void add_start();
void add_end();
void delete_start();
void delete_end();
void print();

int main()
{
    int choice;
    //system("cls");
    system("cls");
    while(1)
    {

        printf("\nEnter choice");
            printf("\n1) Print linked list\n2)Add element at start\n3)Add element at end\n4)Clear linked list\n5)Delete element at start\n6)Delete element at end\n7)Exit the program\n");
            scanf("%d",&choice);

        switch(choice)
        {
            case 1: system("cls");
                print();
                break;

            case 2: system("cls");
                add_start();
                break;
            case 3: system("cls");
                add_end();
                break;
            case 4: start=NULL;
                system("cls");
                printf("\nCleared linked list. (Memory didn't get freed. Wait for update :P)\n");
                break;
            case 5: system("cls");
                delete_start();
                break;
            case 6: system("cls");
                delete_end();
                break;
            case 7: exit(0);
                break;
            default: printf("\nInvalid");
        }

    }
return 0;
}

void add_start()
{

    struct node *new;
    new=(struct node *) (malloc(sizeof(struct node)));

    printf("\nEnter data to add at start:");
        scanf("%d",&(new->data));

    new->next=NULL;
    if(start==NULL)
    {
        start=new;

        return;
    }
    new->next=start;

    start=new;
}

void print()
{
    if(start==NULL)
    {
        printf("\nNo data in Linked List\n");
        return;
    }

        struct node *p;
        p=start;
        printf("\nLinked list: \n");
        while(p!=NULL)
        {
            printf("\n%d",p->data);
            p=p->next;
        }



}

void add_end()
{

        struct node *new;
        new=(struct node *) (malloc(sizeof(struct node)));

    new->next=NULL;
        printf("\nEnter data to add at end:");
        scanf("%d",&(new->data));

    struct node *p;
    p=start;

    if(start==NULL)
    {
        start=new;
        return;
    }

    while(p->next!=NULL)
    {
        p=p->next;
    }

    p->next=new;
}

void delete_start()
 {
    struct node *p;

    if(start==NULL)
     {
         printf("\nLink list is empty\n");
        return;
     }
     else
     {
        p=start;
        start=start->next;
        free(p);
        return;
     }
 }

void delete_end()
 {
     struct node *p,*n;

     if(start==NULL)
     {
         printf("\nLink List Is Empty\n");
         return;
     }
     else
     {
        p=start;

       if(p->next!=NULL)
       {
         while(p->next->next!=NULL)
         p=p->next;

         n=p->next;
         p->next=NULL;

         free(n);

         return;
       }
       else
       {
          start=NULL;
          free(p);
          return;
       }

     }
}