Draw a 3D square using 3D Square and Glut

 #include <GL/glut.h>

/* globals */

GLsizei wh = 500, ww = 500; /* initial window size */
GLfloat size = 3.0;   /* half side length of square */


void drawSquare(int x, int y)
{

	  y=wh-y;
	  glColor3ub( (char) random()%256, (char) random()%256, (char) random()%256);
	  glBegin(GL_POLYGON);
	 	   glVertex2f(x+size, y+size);
		    glVertex2f(x-size, y+size);
	 	   glVertex2f(x-size, y-size);
	    	glVertex2f(x+size, y-size);
	  glEnd();
	  glFlush();
}


/* rehaping routine called whenever window is resized
or moved */

void myReshape(GLsizei w, GLsizei h)
{

/* adjust clipping box */

   	glMatrixMode(GL_PROJECTION);
   	glLoadIdentity(); 
   	glOrtho(0.0, (GLdouble)w, 0.0, (GLdouble)h, -1.0, 1.0);
   	glMatrixMode(GL_MODELVIEW);
   	glLoadIdentity(); 

/* adjust viewport and clear */

	   glViewport(0,0,w,h);
    glClearColor (0.0, 0.0, 0.0, 1.0);
   	glClear(GL_COLOR_BUFFER_BIT);
   	glFlush();

/* set global size for use by drawing routine */

	   ww = w;
   	wh = h; 
}

void myinit(void)
{

   	glViewport(0,0,ww,wh);

/* Pick 2D clipping window to match size of screen window 
This choice avoids having to scale object coordinates
each time window is resized */

   	glMatrixMode(GL_PROJECTION);
   	glLoadIdentity(); 
   	glOrtho(0.0, (GLdouble) ww , 0.0, (GLdouble) wh , -1.0, 1.0);

/* set clear color to black and clear window */

   	glClearColor (0.0, 0.0, 0.0, 1.0);
	   glClear(GL_COLOR_BUFFER_BIT);
	   glFlush();



/* callback routine for reshape event */

   	glutReshapeFunc(myReshape);

}

void mouse(int btn, int state, int x, int y)
{
    if(btn==GLUT_RIGHT_BUTTON && state==GLUT_DOWN)   exit(0);
}

/* display callback required by GLUT 3.0 */

void display(void)
{}

int main(int argc, char** argv)
{

   	glutInit(&argc,argv);
	   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
	   glutCreateWindow("square");
   	myinit ();
   	glutReshapeFunc (myReshape);
   	glutMouseFunc (mouse);
   	glutMotionFunc(drawSquare);
	glutDisplayFunc(display);

   	glutMainLoop();

}