How many kinds of coordinate in openGl?

I know there are view coordinate and world coordinate.
I want to know which point is the orgin point
in the screen and each direction of the “x”,“y”,“z”.
In a sample,there are a SolidSphere ,when the function " glTranslatef(-3.75,3.0,0.0)"
was used ,it appeared on the left-top of the screen, but when
“glTranslatef(-3.75,3.0,0.0)” was used ,it appeared on the right top of the screen,I wonder the width of the screen less than 10.
And where is the orign point ?

The standard OpenGL coordinate system is, I believe, one where:

The X axis runs from left to right, increasing in positive value from left to right.

The Y axis runs from bottom to top, increasing in positive value from bottom to top.

The Z axis runs into and out of the screen, increasing in positive value going out of the screen towards the viewer.

There are a bunch of transformations too -
Viewing - specifies location of camera
Modelling - handles moving of objects in scene
Projection - defines view volume/clip planes
Viewport - maps 2D projection to rendering window


[This message has been edited by Mezz (edited 08-21-2001).]