In gluPersepective() function we define near clipping. In most of the cases we define near clipping as 1.0 which means anything which is beyond 1.0 or which has Z co-ordinate value less than 1.0 will not be drawn then why are the primitives or points are drawn or visible in the screen which have -5.0( or any other negative value for Z-axis)
Because the near/far clipping distances are in eye-space, not model space. The perspective matrix never sees what glVertex gets; it sees those vertices only after they have been transformed by the GL_MODELVIEW matrix. So all of the transforms you set on the modelview matrix happen before the perspective projection.
The bottom line is that glFrustum and gluPerspective generate a right-handed coordinate system. That means that positive z points to you. If you wanna see objects on your screen with your