hai guys, Please say me that what is the POSITION of the (0,0,0) and (0 ,0) in the MONITOR screen that is in OPENGL....... please help me.... regards Tango

Normally its at the top left position on your screen but it can always be normalised to make the screen as in the case of first quadrant. The third zero is the Z-Order.

OpenGL's "origin" is at the bottom-left, as a mathematician would expect. There are simple ways to put it at the upper left, as most windowing systems expect. See here and many other Googled references.