Rotate object around another object - c

Question

I drew two rectangles in my scene, and now I'm trying to rotate one rectangle around the other.
When I press the "Left key" my first rectangle moves in direction to the other, but I don't have the effect of rotate because it is only moving in a straight line in direction of the other rectangle.
How do I change the Z direction of the first rectangle?
tl;dr: It's like a solar system, but I don't understand how can I have the depth effect.
I'm using GLUT and OpenGL.
EDIT: More Info:
This is my current code (function that shows the scene):
void RenderScene(void){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1.0f, 0.0f, 0.0f);
glPushMatrix();
glTranslatef(-70.0f, 0.0f, 0.0f);
glRectf(-25.0f, 25.0f, 25.0f, -25.0f);
glPopMatrix();
glColor3f(1.0f, 1.0f, 0.0f);
glPushMatrix();
glTranslatef(xCor, 0.0f, 0.0f);
glRectf(-25.0f, 25.0f, 25.0f, -25.0f);
glPopMatrix();
glFlush();
}
And a image to help:

Answer 1

Please enable depth test to hide objects beyond other objects.
Give a high value z vaue for the far object.
glEnable( GL_DEPTH_TEST );
glClear( GL_COLOR_BUFFER_BIT |GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glTranslatef(-70.0f, 0.0f, 0.0f);
glRectf(-25.0f, 25.0f, 25.0f, -25.0f);
glPopMatrix();
glColor3f(1.0f, 1.0f, 0.0f);
glPushMatrix();
glTranslatef(xCor, 0.0f, 0.0f);
glRectf(-25.0f, 25.0f, 25.0f, -26.0f); // Z value of behind object is set far from eye
glPopMatrix();

Answer 2

What you want to do is moderately complicated.
The only way I know to locate rectangles in 3-space is to build them using glVertex3f() like this:
glBegin(GL_QUADS);
glVertex3f(x0, y0, z0);
glVertex3f(x1, y1, z1);
glVertex3f(x2, y2, z2);
glVertex3f(x3, y3, z3);
glEnd();
Your "solar system" will have to be located in screen coordinates: X->left/right, Y->up/down, Z->into/out of screen. To create the effect of orbiting, you'll have to recalculate all four X and Z for each movement increment.
I also suggest using gluLookAt() if you want to see a different view.
The man page for glPerspective() says that zNear is always positive but you've given it a negative number. I'd leave that line commented out until I saw some orbiting.
HTH.