DDA line Algo

// implement DDA algorithm
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<graphics.h>
int sign(float x)
{
	int signa;
	if(x>=0.0)
	signa=1;
	else
	signa=-1;
	return signa;
}
void main()
{
	//step 1
	int gd=DETECT,gm;
		float x1,y1,x2,y2,dx,dy,length;
		int i=1;
	float dx1,dy1,x,y;
		int sign(float x);

	initgraph(&gd,&gm,"c:/tc1/tc/tc/bgi");
	printf("enter point 1 \n");
	scanf("%f",&x1);
	scanf("%f",&y1);
	printf("coordinates are %f %f \n",x1,y1);
	printf("enter point 2 \n");
	scanf("%f",&x2);
	scanf("%f",&y2);
	printf("coordinates are %f %f \n",x2,y2);
	//step 2
	if(x2>x1)
	dx=x2-x1;
	else
	dx=x1-x2;
	if(y2>y1)
	dy=y2-y1;
	else
	dy=y1-y2;
	//step3
	if(dx>=dy)
	length=dx;
	else
	length=dy;
	//step 4
	dx1=(x2-x1)/length;
	dy1=(y2-y1)/length;
	//step5
	x=x1+0.5*sign(dx1);
	y=y1+0.5*sign(dy1);



	//step 6
	while(i<=length)
	{

		putpixel((int)x,(int)y,RED);
		x=x+dx1;
		y=y+dy1;
		i=i+1;
	}

	getche();

       closegraph();
	clrscr();


}