Stellar system

The fllowing C program  uses the FreeGLUT package to produce orbits for stellar objects. I have not yet applied Kepler's equations to produce elliptical orbits instead of the circular ones shown. As well as Debian 9 'Stretch' 64 bit Linux, I have got the program to run on the Raspberry Pi with Raspbian 10 'Buster'.
Here are screenshot of the program output:

The program can be compiled by using the syntax

gcc programname.c -o programname -lglut -lGL

Here is the program code


// ----------------------------------------------------------
// Includes
// ----------------------------------------------------------
#include <stdio.h>
#include <stdarg.h>
#include <math.h>
#define GL_GLEXT_PROTOTYPES
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

static GLfloat rot;    //rotation angle
// ----------------------------------------------------------
// Function Prototypes
// ----------------------------------------------------------
void display();



// ----------------------------------------------------------
// display() Callback function
// ----------------------------------------------------------
void display(){

  //  Clear screen and Z-buffer
  glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

  // Reset transformations
  glLoadIdentity();

  // Other Transformations
  // glTranslatef( 0.1, 0.0, 0.0 );      // Not included
  // glRotatef( 180, 0.0, 1.0, 0.0 );    // Not included
 //  glScalef( 2.0, 2.0, 0.0 );          // Not included

    glPushMatrix();//push on stack   
        glTranslatef(0.0, 0.0, -10.0); //move
    glRotatef(rot, 0.0, 1.0, 0.0); //rotation
//    glRotatef(rot*2, 1.0, 0.0, 0.0); //rotation
        glColor3f (1.0, 1.0, 0.0);         
        glutWireSphere(1.0, 20, 50);
        glPopMatrix();    //pop out stack

        glPushMatrix();//push on stack
        glTranslatef(0.0, 0.0, -20.0); //move
    glRotatef(rot*0.4, 0.0, 1.0, 0.0); //rotation
    glTranslatef(7.0, 0.0, -1.5); //move
//    glRotatef(rot*2, 1.0, 0.0, -5.0); //rotation
        glColor3f(0.0, 1.0, 1.0);       
        glutWireSphere(1.0, 20, 50);    
        glPopMatrix();    //pop out stack

        glPushMatrix();//push on stack
        glTranslatef(5.0, 0.0, -20.0); //move
        glRotatef(rot*0.2, 0.0, 1.0, 0.0); //rotation     
        glTranslatef(7.0, 2.0, 2.0); //move
        glColor3f (1.0, 1.0, 0.0);         
        glutSolidSphere(1.0, 20, 50);
        glPopMatrix();    //pop out stack
      

        glPushMatrix();//push on stack
        glTranslatef(5.0, 2.0, -25.0); //move
        glRotatef(rot*0.5, 0.0, 1.0, 0.0); //rotation
        glTranslatef(5.0, 0.0, 2.0); //move
        glTranslatef(7.0, 0.0, 4.0); //move
    //    glRotatef(rot, 0.5, 1.0, 0.0); //rotation
        glColor3f(0.0, 1.0, 1.0);       
        glutWireSphere(1.0, 20, 50);    
        glPopMatrix();    //pop out stack
     
 

        glFlush();
        glutSwapBuffers();  //  Request display update
        glutPostRedisplay();


}

void reshape_func(int width, int height)
{



    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
        glFrustum(-1.0, 1.0, -1.0, 1.0, 3.0, 10000.0);
    glMatrixMode(GL_MODELVIEW);
}

void idle_func(void)
{
    rot=0.1*(GLfloat)glutGet(GLUT_ELAPSED_TIME); //Returns the amount of time (in milliseconds) from the time you call the () glutInit.
    glutPostRedisplay(); //re-draw the screen glut   
}



// ----------------------------------------------------------
// main() function
// ----------------------------------------------------------
int main(int argc, char* argv[]){

  //  Initialize GLUT and process user parameters
  glutInit(&argc,argv);
// glNewList(GLOBE, GL_COMPILE);
  //  Request double buffered true color window with Z-buffer
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
 glutInitWindowSize(600,600);
  // Create window
  glutCreateWindow("Rotating spheres in C");
  //  Enable Z-buffer depth test
  glEnable(GL_DEPTH_TEST);



  // Callback functions
  glutDisplayFunc(display);
  glutReshapeFunc(reshape_func);
  glutIdleFunc(idle_func);
  glEnable(GL_DEPTH_TEST);
  //  Pass control to GLUT for events
  glutMainLoop();

  //  Return to OS
  return 0;

}