linked list insertion operation and display - c

Question

I am trying to implement a singly linked list and performing insertion operations.The program compiles and runs but whenever i try to display its elements.It doesn't show the elements.I am not able to find out the error.
#include <stdio.h>
#include <stdlib.h>
struct n
{
int data;
struct n *next;
};
typedef struct n node;
node *insert_at_front(node *start,int info)
{
node *temp,*p;
temp=(node *)malloc(sizeof(node));
temp->data=info;
temp->next=start;
start=temp;
return start;
}
node *insert_at_end(node *start,int info)
{
node *temp,*p;
temp=(node *)malloc(sizeof(node));
if(start==NULL)
{
printf("Empty\n");
return start;
}
else
{
for(p=start; p->next!=NULL; p=p->next)
{
if(p->next==NULL)
{
temp->data=info;
temp->next=p->next;
p->next=temp;
}
}
}
return start;
}
node *insert_after(node *start,int info,int dat)
{
node *temp,*p;
temp=(node *)malloc(sizeof(node));
for(p=start; p->next!=NULL; p=p->next)
{
if(p->data==dat)
{
temp->data=info;
temp->next=p->next;
p->next=temp;
}
}
return start;
}
void display(node *start)
{
node *temp;
if(start==NULL)
{
printf("List is Empty\n");
return ;
}
temp=start;
while(temp!=NULL)
{
printf("%d-->",temp->data);
temp=temp->next;
}
printf("\n\n");
}
int main()
{
int value;
node *start=NULL;
int choice,data1;
while(1)
{
printf("\n1.insert_at_start\n2.insert at end.\n3.insert_after");
printf("\n4.display\n");
printf("enter choice\n");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("Enter value\n");
scanf("%d",&value);
insert_at_front(start,value);
break;
case 2:
printf("Enter value\n");
scanf("%d",&value);
insert_at_end(start,value);
break;
case 3:
printf("Enter value\n");
printf("Enter value after which you want to insert\n");
scanf("%d%d",&value,&data1);
insert_after(start,value,data1);
break;
case 4:
display(start);
break;
default:
break;
}
}
return 0;
}

Answer 1

One problem with your code is that you're not using the return values from the different insert procedures. This means that if you start with an empty list (NULL) there is no way that main can get a non-empty list back.
At least you need to update start, for example:
start = insert_at_front(start,value);