DDA.c

#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;
}