DDA LIne algorithm using OpenGL

Digital Differential Analyzer (DDA)

<br />#include<GL/glut.h>
#include<stdlib.h>
#include<stdio.h>
float x1,x2,y1,y2;

void display(void)
{
float dy,dx,step,x,y,k,Xin,Yin;
dx=x2-x1;
dy=y2-y1;

if(abs(dx)> abs(dy))
{
step = abs(dx);
}
else
step = abs(dy);

Xin = dx/step;
Yin = dy/step;

x= x1;
y=y1;
glBegin(GL_POINTS);
glVertex2i(x,y);
glEnd();

for (k=1 ;k<=step;k++)
{
x= x + Xin;
y= y + Yin;

glBegin(GL_POINTS);
glVertex2i(x,y);
glEnd();
}


glFlush();
}

void init(void)
{
glClearColor(0.7,0.7,0.7,0.7);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-100,100,-100,100);
}

int main(int argc, char** argv) {
printf("Enter the value of x1 : ");
scanf("%f",&x1);
printf("Enter the value of y1 : ");
scanf("%f",&y1);
printf("Enter the value of x2 : ");
scanf("%f",&x2);
printf("Enter the value of y2 : ");
scanf("%f",&y2);

glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (500, 500);
glutInitWindowPosition (100,100);
glutCreateWindow ("DDA Line Algo");
init();
glutDisplayFunc(display);
glutMainLoop();

return 0;
}

Output :-