C Tutor... C Tutorial....: Implementation of Circular linked List.

#include"stdio.h"
#include"conio.h"
#include"stdlib.h"
#include"alloc.h"
#define null 0
               struct node
               {
               int info;
               struct node *link;
               }*start;
               void main()
               {
               int ch,n,m,position,i;
               last=null;
               while(1)
               {
               printf("1.create
               2.addat
               3.addbt
               4.del
               5.disp
               6.exit
);

               printf("er ur ch");
               scanf("%d",&ch);
               switch(ch)
               {
               case 1:
               printf("er no of itc");
               scanf("%d",&n);
               for(i=0;iinfo=data;
                tmp->link=null;
                if(last==null)
                {
                last=tmp;
                tmp->link=last;
                }
                else
                {
                tmp->link=last->link;
                last->link=tmp;
                last=tmp;
                }}
               
               
                addat(int data)
                {
               
                struct node *q,*tmp;
                tmp=(struct node *)malloc(sizeof(struct node));
                tmp->info=data;
                tmp->link=last->link;
                last->link=tmp;
                }
                addbt(int data,int pos)
                {
                struct node *tmp,*q;
                int i;
                q=last->link;;
                for(i=0;ilink;
                if(q==last->link)
                {
                printf("there r lessthan %d elements",pos);
                return;
                }
                }
                tmp=(struct node *)malloc(sizeof(struct node));
                tmp->link=q->link;
                tmp->info=data;
                q->link=tmp;
                if(q==last)
                last=tmp;
                }
                del(int data)
                {
                struct node *tmp,*q;
                if(last->link==last&&last->info==data)
                {
                tmp=last;
                last=null;
                free(tmp);
                return;
                }
                q=last->link;
               
                if(q->info==data)
                {
                tmp=q;
                last->link=q->link;
                free(tmp);
                return;
                }
                while(q->link!=last)
                {
               
                if(q->link->info==data)
                {
                tmp=q->link;
                q->link=tmp->link;
                free(tmp);
               
                printf("element %d is deleted",data);
                }
                if(q->link->info=data)
                {
                tmp=q->link;
                q->link=last->link;
                free(tmp);
                last=q;
                return;}
                printf("element%d is not found",data);
                }
                disp()
                {
                struct node *q;
                if(last==null)
                {
                printf("list isdempty");
                return;
                }q=last->link;
                while(q!=last)
                {
                printf("%d",q->info);
                q=q->link;
                }
                printf("%d",last->info);
                }