C CODE to draw line using digital differential analyzer (DDA)

#include<iostream.h>

#include<conio.h>

#include<graphics.h>

#include<math.h>

void put_pixel(int x, int y, int col)   

{

 putpixel(x+320, 240-y, col);

}

int round(float x)

{

 double rem = fmod((double)x,1.0);

 if(x<0.5)

   return (floor((double)x));

 else

   return (ceil((double)x));

}

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

{

 int xa,ya,xb,yb;

 setcolor(RED);

 line(320,0,320,480);

 setcolor(BLUE);

 line(0,240,640,240);

 setcolor(WHITE);

 if(x1<x2)

 {

   xa=x1;ya=y1;

   xb=x2;yb=y2;

 }

 else

 {

   xa=x2;ya=y2;

   xb=x1;yb=y1;

 }

 int dx,dy;

 dx=xb-xa;

 dy=yb-ya;

 int steps;

 float x=xa,y=ya;

 if (abs(dx)>abs(dy))

   steps = abs(dx);

 else

   steps = abs(dy);

 float xinc,yinc;

 xinc = 1.0*dx/steps;

 yinc = 1.0*dy/steps;

 put_pixel(xa,ya,15);

A  while(x<xb)

 {

   x+=xinc;

   y+=yinc;

   put_pixel(round(x),round(y),15);

 }

}

void main()

{

 clrscr();

 int x1,y1,x2,y2;

 cout<<"Enter x1,y1 : ";

 cin>>x1>>y1;

 cout<<"Enter x2,y2 : ";

 cin>>x2>>y2;

 int gd = DETECT, gm;

 initgraph(&gd,&gm,"c:\\tc\\bgi");

 dda(x1,y1,x2,y2);

 getch();

 closegraph();

}