opengl program to create cylinder and a parallelopiped

#include<GL/glut.h>
#include<math.h>
#define PI 3.1415926535898
GLint circle_points=100;
float rd=0.2;
float m,n,k=0.5;
int i;

void display(){
glClear(GL_COLOR_BUFFER_BIT);


for(i=0;i<8;i++){
glPushMatrix();
glTranslatef(-0.5,n,0);
glColor3f(0,1.0,0.0);
        glBegin(GL_LINE_LOOP);
          int i;
          float angle;
          glColor3f(1.0,0.0,0.0);

          for(i=0;i<circle_points;i++)
        {
               angle=2*PI*i/circle_points;
               glVertex2f((cos(angle)*rd),(sin(angle)*rd));
        }
         glEnd();
    glFlush();
glPopMatrix();
n=n+0.02;

glPushMatrix();
glTranslatef(k,m,0);
glBegin(GL_LINE_LOOP);
glVertex2f(-0.2,0.2);
glVertex2f(0.2,0.2);
glVertex2f(0.2,-0.2);
glVertex2f(-0.2,-0.2);
glEnd();
glFlush();
glPopMatrix();
m=m+0.02;
k=k+0.01;
}

}



void initGL()
{
glClearColor(1,1,1,1);
glColor3f(1,0,0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-1,1,-1,1,-1,1);
}


int main(int argc, char** argv) {
   glutInit(&argc, argv);       
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize(500,500);
   glutInitWindowPosition(50, 50);
   glutCreateWindow("circle");
   glutDisplayFunc(display);          
   initGL();                  
   glutMainLoop();              
   return 0;
}