3.Bresenham's Line Drawing Algorithm

#include<stdio.h>
#include<math.h>
#include<conio.h>
#include<graphics.h>

void main()
{
int x1,x2,y1,y2;
int gd=DETECT,gm;
void linebres(int,int,int,int);
printf("Enter the two end points:");
scanf("%d%d%d%d",&x1,&x2,&y1,&y2);
initgraph(&gd,&gm,"");
cleardevice();
linebres(x1,y1,x2,y2);
getch();
line(x1,y1,x2,y2);
getch();
closegraph();
}

void linebres(int x1,int y1,int x2,int y2)
{
int dx=abs(x1-x2),dy=abs(y1-y2);
int p,x,y,i,xend,yend;
if(dx!=0)
{
p=2*dy-dx;
if(x1>x2)
{
x=x2;
y=y2;
xend=x1;
}
else
{
x=x1;
y=y1;
xend=x2;
}
putpixel(x,y,2);
for(i=x;i<xend;i++)
{
x+=1;
if(p<0)
p+=2*dy;
else
p+=2*(dy-dx);
}
putpixel(x,y,2);
}
else
{
p=2*dx-dy;
if(y1>y2)
{
x=x2;
y=y2;
yend=y2;
}
putpixel(x,y,2);
for(i=y;i<yend;i++)
{
y+=1;
if(p<0)
p+=2*dx;
else
{
x+=1;
p+=2*(dx-dy);
}
putpixel(x,y,2);
}
}
}