Draw a line using line DDA algorithm

#define ROUND(x) ( (int) (x+0.5) )

#include<stdio.h>

#include<conio.h>

#include<graphics.h>

void lineDDA(int, int, int, int);

void main()

{

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

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

      cleardevice();

      printf("Enter the values for Starting point (X1,Y1) : ");

      scanf("%d %d",&x1,&y1);

      printf("Enter the values for Ending   point (X2,Y2) : ");

      scanf("%d %d",&x2,&y2);

      clrscr();   cleardevice();

      lineDDA(x1,y1,x2,y2);

      getch();

      closegraph();

}

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

{

      int dx = x2-x1, dy = y2-y1, step, i;

      float xIncr, yIncr, x=x1, y=y1;

      int midx = getmaxx()/2, midy = getmaxy()/2;

            /* Co-ordinate Axis */

      line(midx,0,midx,2*midy);

      line(0,midy,2*midx,midy);

      outtextxy(midx+20,midy+20,"(0,0)");

      outtextxy(midx+310,midy+20,"X");

      outtextxy(midx+20,midy-230,"Y");

            /* Start & End Points */

      printf("Start = (%d,%d)",x1,y1);

      printf("\nEnd   = (%d,%d)",x2,y2);

      putpixel(midx+x1,midy-y1,15);

      putpixel(midx+x2,midy-y2,15);

      outtextxy(midx+x1+20,midy-y1,"Start");

      outtextxy(midx+x2+20,midy-y2,"End");

      getch();

      if (abs(dx) > abs(dy))

            step = abs(dx);

      else

            step = abs(dy);

      xIncr = dx / (float) step;

      yIncr = dy / (float) step;

      putpixel(midx+ROUND(x),midy-ROUND(y),4);

      for(i=0 ; i<step ; i++)

      {

            delay(50);

            x += xIncr;

            y += yIncr;

            putpixel(midx+ROUND(x),midy-ROUND(y),4);

      }

}