OpenGL Rotating Cube Code

#include<GL/glut.h>
#include<iostream>
#include<dos.h>
#include<time.h>
using namespace std;


GLfloat angle = 0.0;



void spin(void) {
angle = angle + 0.1;
glutPostRedisplay();
}

void display(void)
{
glClearColor(1,1,0,10);
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
gluLookAt(0.0, 0.0, 10, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

glRotatef(angle,1,0,0);
//glRotatef(angle, 0, 1, 0);
//glRotatef(angle,0, 0, 1);
glColor3d(1.0, 0.0, 0.0);
glutWireCube(6.0);
glColor3d(1.0, 0.0, 0.0);

glutWireCube(5.0);
glColor3d(0, 1.0, 0.0);

glutWireCube(4.0);

glColor3d(0, 1.0, 0.0);
glutWireCube(3.0);

glColor3d(0, 0.0, 1.0);
glutWireCube(2.0);
glColor3d(0, 0.0, 1.0);

glutWireCube(1.0);
glutWireCube(1.0);
glColor3d(1, 1, 1.0);

glFlush();

}
void keyboard(unsigned char key, int x, int y)
{
if (key == 27)
exit(0);


}
void reshape(int width, int height)
{
glViewport(0, 0, (GLsizei)width, (GLsizei)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(70, (GLfloat)width / (GLfloat)height, 1.0, 100.0);


glMatrixMode(GL_MODELVIEW);
}
int main(int argc,char * argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(400, 400);
glutInitWindowPosition(600, 100);
glutCreateWindow("Hellow World...!");
glutDisplayFunc(display);
glutKeyboardFunc(keyboard);
glutReshapeFunc(reshape);
glutIdleFunc(spin);
glutMainLoop();
return 0;
}