Backword Method

/*Backwad Method. */

#include<stdio.h>
#include<conio.h>
void main()
{
int n,i,j;
float x[10],y[10],xx,yy,d[3][10],u,t;
clrscr();
printf("No of pairs of points ");
scanf("%d",&n);
for(i=0;i<n;i++)
{
printf("%dth value of x , y wanted", i+1);
scanf("%f%f", &x[i],&y[i]);
}
for(i=0;i<3&& i<n-1;i++)
for(j=0;j<n-1;j++)
if(i==0)
d[i][j]=y[j+1]-y[j];
else
d[i][j]=d[i-1][j+1]- d[i-1][j];
printf("Give value of x for whichy to be interpolated");
scanf("%f",&xx);
u=(xx-x[n-1])/(x[1]-x[0]);
yy=y[n-1];
t=1;
for(i=0;i<3&&i<n-1;i++)
{
t*=(u+i)/(i+1);
yy+=t*d[i][n-i-2];
}
printf("x=%f\t y=%f\n",xx,yy);
getch();
}