DSA: Addn of Polynomial using LL

#include<stdio..h>
#include<conio.h>
#include<malloc.h>

struct node
{
    int coef;
    int expo;
    struct node *link;
};
struct node *poly_add(struct node *,struct node *);
//struct node *poly_sub(struct node *,struct node *);

struct node *enter(struct node *);
struct node *insert(struct node *,float,int);
void display(struct node *);
void main()
{
    struct node *p1_start;
    struct node *p2_start;
    struct node *p3_start;
    struct node *p4_start;

    clrscr();
    p1_start=NULL;
    p2_start=NULL;
    p3_start=NULL;
    //p4_start=NULL;

    printf("Polynomial 1:\n");
    p1_start=enter(p1_start);
    printf("Polynomial 2:\n");
    p2_start=enter(p2_start);
    p3_start=poly_add(p1_start,p2_start);
    //p4_start=poly_sub(p1_start,p2_start);
    printf("Polynomial 1 : ");
    display(p1_start);
    printf("Polynomial 2 : ");
    display(p2_start);
    printf("Added Polynomial : ");
    display(p3_start);
    /*printf("Subtracted Polynomial : ");
    diplay(p4_start);*/
    getch();
}
struct node *enter(struct node *start)
{
    int i,n,ex,co;
    printf("How many Time You Want To Enter\n");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        printf("Co-efficient of Term %d : ",i);
        scanf("%d",&co);
        printf("Expo of Term %d : ",i);
        scanf("%d",&ex);
        start=insert(start,co,ex);
    }
    return start;
}

struct node *insert(struct node *start,float co,int ex)
{
    struct node *ptr,*t;
    t=(struct node *)malloc(sizeof(struct node));
    t->coef=co;
    t->expo=ex;

    if(start==NULL||ex>start->expo)
    {
        t->link=start;
        start=t;
    }
    else
    {
        ptr=start;
        while(ptr->link!=NULL &&ptr->link->expo>ex)
        {
            ptr=ptr->link;
        }
        t->link=ptr->link;
        ptr->link=t;
        if(ptr->link==NULL)
        {
            t->link=NULL;
        }
    }
    return start;
}
struct node *poly_add(struct node *p1,struct node *p2)
{
    struct node *p3_start,*p3,*t;
    p3_start=NULL;
    if(p1==NULL&&p2!=NULL)
        return p3_start;
    while(p1!=NULL&&p2!=NULL)
    {
        t=malloc(sizeof(struct node));
        if(p3_start==NULL)
        {
            p3_start=t;
            p3=p3_start;
        }
        else
        {
            p3->link=t;
            p3=p3->link;
        }
        if(p1->expo>p2->expo)
        {
            t->coef=p1->coef;
            t->expo=p1->expo;
            p1=p1->link;
        }
        else
        {
            if(p2->expo>p1->expo)
            {
                t->coef=p2->coef;
                t->expo=p2->expo;
                p2=p2->link;
            }
            else
            {
                if(p1->expo==p2->expo)
                {
                    t->coef=p1->coef+p2->coef;
                    t->expo=p1->expo;
                    p1=p1->link;
                    p2=p2->link;
                }
            }
        }
    }//end of while

    while(p1!=NULL)
    {
        t=malloc(sizeof(struct node));
        t->coef=p1->coef;
        t->expo=p1->expo;
        if(p3_start==NULL)
        {
            p3_start=t;
            p3=p3_start;
        }
        else
        {
            p3->link=t;
            p3=p3->link;
        }
        p1=p1->link;
    }//end of while
    while(p2!=NULL)
    {
        t=malloc(sizeof(struct node));
        t->coef=p2->coef;
        t->expo=p2->expo;
        if(p3_start==NULL)//poly 1 is empty
        {
            p3_start=t;
            p3=p3_start;
        }
        else
        {
            p3->link=t;
            p3=p3->link;
        }
        p2=p2->link;
    }//end of while
    p3->link=NULL;
    return p3_start;
}
void display(struct node *ptr)
{
    if(ptr==NULL)
    {
        printf("Empty\n");
        return ;
    }
    while(ptr!=NULL)
    {
        printf("(%dx^%d)",ptr->coef,ptr->expo);
        ptr=ptr->link;
    }
    printf("\b\b\n");/*\b\bto erase the last+sign*/
}