mid point line algorithm in c

#include<stdio.h>
void main()
{
    int x1,x2,y1,y2,di_x,di_y,dpnew,dpinit;
    printf("x1:");
    scanf("%d",&x1);

    printf("y1:");
    scanf("%d",&y1);

    printf("x2:");
    scanf("%d",&x2);

    printf("y2:");
    scanf("%d",&y2);
    di_x=x2-x1;
    di_y=y2-y1;
    dpinit=2*di_y-di_x;
    printf(" initial point %d %d \n",x1,y1);
    while(x1<x2)
    {

        if (dpinit>0)
        {
            x1++;
            y1++;
            printf("%d %d \n",x1,y1);
            dpnew=dpinit+2*(di_y-di_x);

        }
        else
        {
            x1++;
            printf("%d %d \n",x1,y1);
            dpnew=dpinit+2*di_y;
        }

    }


}