Bresenham's line drawing algorithm program in c

/*
Bresenham's line drawing algorithm
Created by: Pirate
*/

#include<stdio.h>

#include<conio.h>

#include<graphics.h>

void bre_line(int x1,int y1,int x2,int y2);

void main()

{

            int x1,x2,y1,y2,gmode=DETECT,gd;

            clrscr();

            initgraph(&gmode,&gd,"c:\\tc\\bgi");

            printf("*** Bresenham Line Drawing algorithm ***");

            printf("\nEnter the starting point of line\n");

            scanf("%d %d",&x1,&y1);

            printf("\nEnter the ending point of line\n");

            scanf("%d %d",&x2,&y2);

            bre_line(x1,y1,x2,y2);

            getch();

}

void bre_line(int x1,int y1,int x2,int y2)

{

            int dx=x2-x1,dy=y2-y1;

            int p=2*dy-dx,i=dx;

            while(i>0)

            {

                        putpixel(x1,y1,7);

                        if(p<0)

                        {

                                    x1=x1+1;

                                    p=p+2*dy;

                        }

                        else

                        {

                                    x1=x1+1;

                                    y1=y1+1;

                                    p=p+2*dy-2*dx;

                        }

                        i--;

            }
}

Output